Association of Molecular Subtypes with Pathologic Response, PFS, and OS in a Phase II Study of COXEN with Neoadjuvant Chemotherapy for Muscle-invasive Bladder Cancer

PURPOSE

The Coexpression Extrapolation (COXEN) gene expression model with chemotherapy-specific scores [for methotrexate, vinblastine, adriamycin, cisplatin (ddMVAC) and gemcitabine/cisplatin (GC)] was developed to identify responders to neoadjuvant chemotherapy (NAC). We investigated RNA-based molecular subtypes as additional predictive biomarkers for NAC response, progression-free survival (PFS), and overall survival (OS) in patients treated in S1314.

EXPERIMENTAL DESIGN

A total of 237 patients were randomized between four cycles of ddMVAC (51%) and GC (49%). On the basis of Affymetrix transcriptomic data, we determined subtypes using three classifiers: TCGA (k = 5), Consensus (k = 6), and MD Anderson (MDA; k = 3) and assessed subtype association with path response to NAC and determined associations with COXEN. We also tested whether each classifier contributed additional predictive power when added to a model based on predefined stratification (strat) factors (PS 0 vs. 1; T2 vs. T3, T4a).

RESULTS

A total of 155 patients had gene expression results, received at least three of four cycles of NAC, and had pT-N response based on radical cystectomy. TCGA three-group classifier basal-squamous (BS)/neuronal, luminal (Lum), Lum infiltrated, and GC COXEN score yielded the largest AUCs for pT0 (0.59, P = 0.28; 0.60, P = 0.18, respectively). For downstaging (

CONCLUSIONS

The Consensus classifier, based in part on the TCGA and MDA classifiers, modestly improved prediction for pathologic downstaging but subtypes were not associated with PFS or OS.

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Key Words Collapse

MESH Headings

• Humans
• Cisplatin/therapeutic use
• Cystectomy/methods
• Deoxycytidine/therapeutic use
• Muscles/pathology
• Neoadjuvant Therapy/methods
• Neoplasm Invasiveness
• Progression-Free Survival
• Retrospective Studies
• Urinary Bladder Neoplasms/drug therapy
• Urinary Bladder Neoplasms/genetics
• Urinary Bladder Neoplasms/pathology

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Grants

• UG1 CA233320 NCI NIH HHS
• UG1 CA233324 NCI NIH HHS
• UG1 CA180830 NCI NIH HHS
• UG1 CA233160 NCI NIH HHS
• U10 CA032102 NCI NIH HHS
• UG1 CA233196 NCI NIH HHS
• U10 CA180888 NCI NIH HHS
• U24 CA114748 NCI NIH HHS
• U10 CA180819 NCI NIH HHS
• UG1 CA233328 NCI NIH HHS

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Affiliation(s)

Seth P. Lerner Baylor College of Medicine, Houston, TX
David J. McConkey Johns Hopkins School of Medicine, Baltimore, MD
Catherine M. Tangen Fred Hutchinson Cancer Research Center, Seattle, WA
Joshua J Meeks Department of Urology, Feinberg School of Medicine, Northwestern University, Chicago, IL
Thomas W. Flaig University of Colorado, School of Medicine, University of Colorado, Aurora, CO
X Hua Fred Hutchinson Cancer Research Center, Seattle, WA
Siamak Daneshmand Department of Urology, Keck School of Medicine, University of Southern California, Los Angeles, CA
Ajjai Shivaram Alva University of Michigan, Ann Arbor, MI
M. Scott Lucia University of Colorado, School of Medicine, University of Colorado, Aurora, CO
Dan Theodorescu Cedars-Sinai CANCER, Los Angeles, CA
Amir Goldkorn University of Southern California, Los Angeles, CA
Matthew I. Milowsky University of North Carolina Lineberger Comprehensive Cancer Center, Chapel Hill, NC
W. Choi Johns Hopkins School of Medicine, Baltimore, MD
Rick Bangs SWOG Cancer Research Network, Portland, OR
Daniel L. Gustafson Colorado State University, Fort Collins, CO
Melissa Plets Fred Hutchinson Cancer Research Center, Seattle, WA
Ian M. Thompson CHRISTUS Medical Center Hospital, University of Texas Health Science Center at San Antonio, San Antonio, TX

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Long-term Outcomes from a Phase 2 Study of Neoadjuvant Chemotherapy for Muscle-invasive Bladder Cancer (SWOG S1314; NCT02177695)

BACKGROUND

The COXEN gene expression model was evaluated for prediction of response to neoadjuvant chemotherapy for muscle-invasive bladder cancer (MIBC).

OBJECTIVE

To conduct a secondary analysis of the association of each COXEN score with event-free survival (EFS) and overall survival (OS) and by treatment arm.

DESIGN, SETTING, AND PARTICIPANTS

This was a randomized phase 2 trial of neoadjuvant gemcitabine-cisplatin (GC) or dose-dense methotrexate-vinblastine-adriamycin-cisplatin (ddMVAC) in MIBC.

INTERVENTION

Patients were randomized to ddMVAC (every 14 d) or GC (every 21 d), both for four cycles.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

EFS events were defined as progression or death before scheduled surgery, a decision to not undergo surgery, recurrence, or death due to any cause after surgery. Cox regression was used to evaluate the COXEN score or treatment arm association with EFS and OS.

RESULTS AND LIMITATIONS

A total of 167 evaluable patients were included in the COXEN analysis. The COXEN scores were not significantly prognostic for OS or EFS in the respective arms, but the GC COXEN score had a hazard ratio (HR) of 0.45 (95% confidence interval [CI] 0.20-0.99; p = 0.047) when the arms were pooled. In the intent-to-treat analysis (n = 227), there was no significant difference between ddMVAC and GC for OS (HR 0.87, 95% CI 0.54-1.40; p = 0.57) or EFS (HR 0.86, 95% CI 0.59-1.26; p = 0.45). Among the 192 patients who underwent surgery, pathologic response (pT0 vs downstaging vs no response) was strongly correlated with superior postsurgical survival (5-yr OS 90%, 89% and 52%, respectively).

CONCLUSIONS

The COXEN GC score has prognostic value for patients receiving cisplatin-based neoadjuvant treatment. The randomized, prospective design provides estimates of OS and EFS for GC and ddMVAC in this population. Pathologic response (

PATIENT SUMMARY

In this study, we evaluated a biomarker to predict the response to chemotherapy. The results did not meet the preset study parameters, but our study provides information on clinical outcomes with the use of chemotherapy before surgery for bladder cancer.

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Key Words

• Biomarkers
• Cystectomy
• Neoadjuvant chemotherapy
• Urinary bladder cancer

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MESH Headings

• Humans
• Cisplatin
• Cystectomy/methods
• Deoxycytidine/therapeutic use
• Muscles/pathology
• Neoadjuvant Therapy/methods
• Neoplasm Invasiveness
• Retrospective Studies
• Treatment Outcome
• Urinary Bladder Neoplasms/drug therapy
• Urinary Bladder Neoplasms/surgery
• Urinary Bladder Neoplasms/pathology

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Grants

• U10 CA180821 NCI NIH HHS
• UG1 CA233324 NCI NIH HHS
• UG1 CA180830 NCI NIH HHS
• UG1 CA233160 NCI NIH HHS
• UG1 CA233373 NCI NIH HHS
• UG1 CA233196 NCI NIH HHS
• U10 CA180820 NCI NIH HHS
• U10 CA180888 NCI NIH HHS
• U10 CA180819 NCI NIH HHS
• UG1 CA233328 NCI NIH HHS

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Affiliation(s)

Thomas W Flaig School of Medicine, University of Colorado, Aurora, CO, USA.
Catherine M Tangen Fred Hutchinson Cancer Research Center, Seattle, WA, USA
Siamak Daneshmand Department of Urology, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
Ajjai Shivaram Alva University of Michigan, Ann Arbor, MI, USA
M Scott Lucia School of Medicine, University of Colorado, Aurora, CO, USA
David James McConkey Johns Hopkins School of Medicine, Baltimore, MD, USA
Dan Theodorescu Cedars-Sinai Cancer, Los Angeles, CA, USA
Amir Goldkorn Division of Medical Oncology, Department of Medicine, Keck School of Medicine and Norris Comprehensive Cancer Center, University of Southern California, Los Angeles, CA, USA
Matthew I Milowsky University of North Carolina Lineberger Comprehensive Cancer Center, Chapel Hill, NC, USA
Rick Bangs Southwestern Oncology Group, San Antonio, TX, USA
Gary R MacVicar Illinois CancerCare PC, Peoria, IL, USA
Bruno R Bastos Cleveland Clinic Florida, Weston, FL, USA
Jared S Fowles Colorado State University, Fort Collins, CO, USA
Daniel L Gustafson Colorado State University, Fort Collins, CO, USA
Melissa Plets Fred Hutchinson Cancer Research Center, Seattle, WA, USA
Ian M Thompson CHRISTUS Medical Center Hospital, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
Seth P Lerner Scott Department of Urology, Dan L Duncan Cancer Center, Baylor College of Medicine, Houston, TX, USA

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Clinical implications of Wnt signaling alterations in patients (pts) with advanced prostate cancer (aPC)

229

Background: Aberrant Wnt signaling has been implicated in prostate cancer tumorigenesis, progression, and metastasis in preclinical models. While studies have identified recurrent molecular alterations in the Wnt signaling components in about 20% of aPC pts, the clinical significance of these alterations has been incompletely characterized. Methods: PROMISE is a multi-institutional, retrospective, clinical-genomic database - inclusive of aPC pts who had tissue and/or blood-based genomic testing by commercially available CLIA-certified platforms. We evaluated outcomes in pts with alterations leading to the activation of the canonical Wnt pathway, specifically activating mutations in CTNNB1 or RSPO2 or inactivating mutations in APC, RNF43, or ZNRF3 (Wnt altered), compared to those lacking such alterations (Wnt wild type). Multiple endpoints were evaluated, including the frequency of metastatic disease to different sites and co-occurring alterations. Results: 1596 pts with aPC were included with a median age of 63 years at diagnosis. Wnt pathway alterations were identified in 12.4% (198/1596). Wnt altered pts had a statistically significant increase in liver and lung metastases compared with Wnt wild type pts at diagnosis (4.5% vs 2.1%, p=0.0438; 6.1% vs 2.9%, p=0.0292), at first metastatic disease (11.6% vs 5.4%, p= 0.0015; 14.8% vs 6.6%, p<0.0001), and at diagnosis of CRPC (14.2% vs 7.9%, p=0.01436; 16.1% vs 6.8%, p=0.0003). Fewer Wnt altered pts had bone metastases at CRPC compared with wild type pts (67.7% vs 75.2%, p=0.04948) without significant difference of bone metastases at the time of diagnosis or at the time of first metastatic disease. The frequency of metastases to other sites was similar between the cohorts. More Wnt altered pts had ductal features on histology at diagnosis compared with Wnt wild type pts (4.0% v 1.6%, p=0.02415) without difference in PSA, Gleason score, TNM stage, or presence of neuroendocrine or intraductal features. Co-occurring genomic alterations that were more common in Wnt altered pts included PTEN loss/mutation (25.3% vs 18.3%, p=0.0270), RB1 loss/mutation (10.6% vs 5.8%, p=0.0079), AR mutations or gain (37.9% vs 24.0%, p< 0.0001), and SPOP mutations (14.1% vs 3.9%, p< 0.0001) as compared with Wnt wild type pts. Conclusions: Wnt pathway alterations were associated with ductal histology, an increase in visceral metastases at all time points evaluated, and an increase in co-occurring PTEN, RB1, AR, and SPOP alterations. The clinical heterogeneity of aPC and differences in co-occurring mutations between the cohorts make isolating the effect of alterations in a single pathway challenging. Analysis of overall survival outcomes is currently in process, and future multivariable analysis is planned to adjust for established clinical factors and co-occurring mutations to identify the independent contributions of Wnt alterations to clinical outcomes.

Clinical impact of mutations in driver oncogenes and TP53/RB1 in advanced prostate cancer

263

Background: Prostate cancer (PCa) is characterized by considerable genetic heterogeneity, and complex genomic features may influence prognosis and treatment response. We created a database of aggressive PCa that integrates comprehensive genomic sequencing with detailed clinical outcomes to better understand the optimal use of genomic sequencing. Methods: From 4/2005-7/2021, PCa cancer patients older than 18 years of age underwent tissue collection for tumoral RNA-sequencing and tumor/normal whole exome sequencing at our institution (HUM00046018, HUM00048105, HUM00067928, SU2C). Genomic and transcriptomic sequencing data was processed using Turnkey Precision Oncology. Genetic alterations, including ETS fusions, SPOP, FOXA1 class 1, and CDK12 mutations, as well as TP53 and RB1 mutations were analyzed. Clinical data was collected from 05/2021-01/2022, and clinical associations (metastasis free survival (MFS), time to castrate resistant prostate cancer (CRPC), and overall survival (OS)) were determined. Results: Data was available for 325 men. Median follow up from diagnosis was 106 months (IQR, 90-121), median age at diagnosis was 61 (IQR, 54-67), and most (91%) presented with PCa adenocarcinoma (n=292/325). At diagnosis, 51% (n=165) had localized, 5% (n=18) had clinical node positive, and 40% (n=128) had de-novo M1 disease. At time of tissue sampling, 87% (n=283) had metastatic disease, and 59% (n=192) were castrate resistant. Established PCa driver mutations included 140 ETS fusions (49%), 26 SPOP mutations (9%), 22 FOXA1 class 1 mutations (8%), and 15 (5%) CDK12 mutations. For men with localized disease at diagnosis (n=197/325), ETS fusion was associated with improved MFS (HR: 0.55; 95% CI: 0.37-0.81), time to CRPC (HR: 0.53; 0.35-0.80), and OS (HR: 0.56; 0.35-0.89). SPOP mutations were also associated with improved prognosis in this population (n=197/325): MFS (HR: 0.45; 0.24-0.84), time to CRPC (HR: 0.36; 0.18-0.73), and OS (HR: 0.46; 0.21-0.99). TP53 mutations were identified in 38% (n=122) of all patients and were associated with worse OS from the time of biopsy after adjusting for PCa castration state and disease spread at biopsy (HR: 2.2; 1.7-2.9, p<0.001). RB1 mutations were identified in 12% (n=40; 24/40 also TP53 mutants). OS from the time of biopsy was worse in the presence of dual TP53/RB1 mutants when compared to TP53 or RB1 mutants alone, independent of the disease state at time of biopsy (HR, 4.3; 95%CI: 2.7-7.0). Conclusions: In a cohort of aggressive PCa, oncogenic driver mutations were associated with significant differences in prognosis. ETS fusions and SPOP mutations correlated with improved outcomes for men with localized disease at presentation. TP53 loss was associated with worse prognosis, as was the combination with RB1 loss, across the disease spectrum. Future efforts will focus on correlating sensitivity to PCa treatments with genetic alterations throughout the disease course.

Evaluating the clinical utility of circulating tumor cells (CTC) profiling to predict selection of preferred therapeutic regimens in newly diagnosed or pretreated refractory renal cell carcinomas (RCC)

717

Background: There is an unmet need for biomarkers enabling therapeutic selection and prediction of clinical outcomes in kidney cancer . We evaluated the feasibility and utility of profiling of circulating tumor cells (CTCs) via multiplexed fluorescence immunocytochemistry (ICC) to identify liquid biopsy biomarkers linked to treatment response (or resistance) in advanced RCC patients. In addition, transcriptome analysis for 20802 genes from exosomal RNA is planned to evaluate novel prognostic and predictive signatures. Methods: Patients with either untreated or pretreated advanced RCC were eligible prior to starting a new systemic therapy regimen. IRB approved written informed consent was obtained. Serial blood samples were collected at baseline, and at 3, 6, 12 and 24 months. Primary endpoint of the study was to detect the proportion of patients with RCC in whom CTCs can be detected and profiled. Secondary endpoints are to correlate the profiling and changes in CTC with response and clinical outcomes. The study will meet its primary endpoint if the assay provides adequate detection and profiling for at least 12 patients. With an overall sample size of 50 the width of a 95% confidence interval for the rate of providing a therapeutic intervention is guaranteed to be less than 26%. Results: 44 evaluable patients have been enrolled; 11 females, 33 males. Median age was 64 years (range 40-85 years). 38 white patients, 2 black patients and 4 of other ethnicity have been enrolled.16 patients were untreated, 22 were pretreated and 6 were undergoing adjuvant therapy post nephrectomy. 37 patients had clear cell histology, 4 non clear cell and 3 unclassified histology. 42 of the 44 (95.5%) patients had detectable CTCs in the baseline sample. 21 on treatment samples have been collected to date, with detectable CTCs in all except one sample. 53 of 65 samples (81.5%) demonstrated detection of at least one biomarker by ICC. VEGFA expression was the most commonly detected biomarker on ICC (detected in 28 of 63 samples). Conclusions: The primary endpoint was met, and feasibility of the test was demonstrated with 95% of the baseline samples showing CTC detection and 81.5% showing biomarker expression. This blood-based, non-invasive liquid biopsy demonstrated high sensitivity for detection of cancer cells, and presents a potential opportunity for biomarker profiling to predict therapeutic efficacy of conventional RCC therapeutic agents. Correlation of longitudinal CTC with clinical outcomes will be reported. Transcriptome analysis is under evaluation for novel prognostic and predictive signatures and will be reported.

Biomarkers of response to enfortumab vedotin (EV) in patients (pts) with advanced urothelial carcinoma (aUC): Analysis of the UNITE study

450

Background: EV, an antibody-drug conjugate (ADC) targeting Nectin-4, is used widely in treatment-refractory aUC, but limited data are available on biomarkers predictive of EV outcomes. We investigated potential biomarkers of response to EV in a pt cohort in the UNITE dataset. Methods: We included the retrospective UNITE study pts from 16 sites, with available next generation sequencing using institutional or commercial platforms, treated with EV alone outside clinical trials. Observed response (ORR) was determined by investigators for evaluable pts with scans after ≥1 dose of EV. Assessed molecular biomarkers included tumor mutation burden (TMB), PD-L1 status, somatic alterations (alts) in ≥ 10% of pts ( TERTp, TP53, ARID1A, CDKN2A, CDKN2B, FGFR3, ERBB2, CCND1, KDM6A, MTAP, PIK3CA, RB1, TSC1) and presence of ≥1 DNA damage response mutations ( ATM, BARD1, BRCA1, BRCA2, CDK12, CHEK2, PALB2, PPP2R2A, or RAD51B). ORRs were compared using Chi-squared test, while median progression-free and overall survival (mPFS, mOS) from EV start were compared with log-rank test and Cox proportional hazards in pts with and without biomarker presence. Results: A total of 170 pts had outcomes and NGS data available. Median age was 70, 133 (78%) were men, 144 (85%) Caucasian, 110 (65%) with pure urothelial histology, 118 (69%) with primary bladder tumor, and 116 (68%) had ≥ 2 lines of therapy before EV. For all pts, ORR 47%, mPFS 6 mos, mOS 12 mos. ORRs were higher in pts with ERBB2 (67% vs 44%; p = 0.05) and TSC1 (68% vs 25%; p=0.04) alts vs wild-type. Shorter mPFS was noted in pts with CDKN2A, CDKN2B, and MTAP alts, and longer mOS in pts with high TMB (table). Conclusions: This large, multi-site, retrospective cohort of pts with aUC identified several potential biomarkers associated with differential outcomes to EV. These findings, upon external validation, may help inform clinical decision making and potential therapy sequencing with available ADCs. Limitations include retrospective nature, pt selection, and confounding biases. [Table: see text]

Outcomes Database to Prospectively Assess the Changing Therapy Landscape in Renal Cell Carcinoma (ODYSSEY RCC)

TPS739

Background: The landscape for treatment of metastatic renal cell carcinoma (mRCC) has changed dramatically over the past 7 years with the approvals of tyrosine kinase inhibitors and immune-oncology (IO) agents alone or in combination for untreated mRCC. However, multiple knowledge gaps remain. While active surveillance remains an option for selected pts, prospective evidence on selection of and outcomes for pts is limited. Recent phase III trials all used a common comparator, sunitinib, so no comparative effectiveness data on the new IO-based regimens exists. There are also no routinely used predictive biomarkers in mRCC pt management. Therefore, a better understanding of the biologic determinants associated with cancer heterogeneity and clinical outcomes through blood, tumor, and radiographic based assessments is needed. Importantly, longitudinal changes in health-related quality of life (QOL) and symptom burden of patients with mRCC initiated on new IO–based regimens outside of an interventional clinical trial are poorly understood. Pt reported outcomes (PRO) are rarely captured in a systematic manner. Addressing the evidence gap for how real world pts symptomatically change with treatment combinations and sequences over time is a pressing unmet need. Methods: This is a prospective, observational cohort, phase IV study of 800 mRCC pts in the US. Pts must: be age ≥19 at informed consent; have a diagnosis of mRCC (any histology) with no prior systemic therapy for mRCC (surgery and radiation therapy, prior neoadjuvant/adjuvant therapy for non-mRCC, and pts currently not on systemic therapy and being observed are all permitted); and be able to comply with completion of PROs. Those being treated for active malignancies other than mRCC or not intending to undergo follow up care at a study site within PCORnet are excluded. Pts will undergo consent and baseline assessments, including research blood collection and processing, by the study site team. A novel aspect of this study is the use of PCORnet and Medicare data to minimize data collection burden on sites. PCORnet, the National Patient-Centered Clinical Research Network, is a network of networks that curates EHR data from multiple health systems using a common data model. This allows subsequent follow up to be centrally coordinated by the coordinating center. PRO will be collected at baseline (pre-treatment), every 3 mos for 2 yrs, and then every 6 mos until end of follow up (minimum 18 mos follow-up; maximum 36 mos follow-up). The primary objective is to determine distinct patterns of change in QOL and symptom burden of mRCC pts receiving therapy. Secondary objectives include quantifying the time to treatment discontinuation of pts, identifying patterns of clinical management in the real world setting of mRCC pts on various treatment regimens, and evaluating overall survival of mRCC pts. ClinicalTrials.gov Identifier: NCT04919122 Clinical trial information: NCT04919122 .

Enfortumab vedotin (EV) outcomes with and without immediate prior immune checkpoint inhibitor (ICI) in patients (pts) with advanced urothelial carcinoma (aUC)

514

Background: EV is FDA-approved in pts with aUC and ≥1 prior therapy line. Data from EV-103 trial indicate robust response to first-line EV/pembrolizumab, suggesting potentially at least additive treatment effect with EV/ICI combination. Given the long half-life of ICIs, pts who start EV treatment immediately after ICI may potentially derive benefit from that therapy sequence. We hypothesized that the last systemic therapy prior to EV would impact outcomes, as pts treated with ICI immediately prior to EV would have superior outcomes relative to pts treated with chemotherapy (chemo). Methods: UNITE is a retrospective study of pts treated with EV at 16 US sites. Pt characteristics and outcomes were abstracted from EMR review at each site. Observed response was determined by investigators for evaluable pts with scans following ≥1 EV dose. Pts treated with EV monotherapy were divided into two groups based on whether they received chemo or ICI as the line of therapy immediately prior to EV, regardless of other therapy received. Chi-squared test was used to assess differences in pt characteristics and ORR while log-rank tests were used for OS and PFS measured from EV start. Results: Among 325 pts treated with EV monotherapy, 247 had chemo or ICI as immediate prior treatment, with 186 pts receiving ICI (Group A) and 61 pts receiving platinum-based chemo (Group B). In 247-pt cohort, ORR to EV was 52% and mPFS and mOS were 6 and 13 mos. Group B pts were younger, had more bone mets and higher Bellmunt risk factors, but were otherwise similar to Group A (Table). Most pts had both prior chemo and ICI in both group A (58%) and group B (84%). Group A pts had shorter time from last treatment (median 1.2 vs 3.2 mo, p<0.01), lower ORR to immediate prior treatment (16% vs 37%, p<0.01) and fewer prior therapy lines (mean 1.9 vs 2.6, p<0.01). Group A had superior ORR (58% vs 37%, p=0.02), mPFS (6.9 vs 4.8 mo, p=0.02) and mOS (15.2 vs 8.8 mo, p=0.01) from EV start vs Group B. Conclusions: Pts with aUC treated with EV had superior outcomes if they received ICI instead of chemo as immediate prior treatment, suggesting the hypothesis that this may represent an optimal therapy sequence or combination. These data need external validation as limitations include retrospective design, lack of randomization, and selection and confounding biases. [Table: see text]

Final results of phase Ib/II study of durvalumab and guadecitabine in advanced clear cell renal cell carcinoma (ccRCC) and biomarker analysis

696

Background: Hypomethylating agents (HMA) can augment the anti-tumor immune response. Guadecitabine (G) is a novel HMA shown to induce a dose-dependent decrease of global DNA and gene-specific methylation in pre-clinical models. Methods: This is phase Ib/II clinical trial of Guadecitabine (G) and Durvalumab (D) in advanced ccRCC. Phase Ib tested two doses of G, de-escalated from 60 mg/m2 to 45 mg/m2 in combination with standard dose of D. Followed by two cohorts in phase II. Cohort 1 (C1, CPI naïve) allowed up to one prior line of treatment and Cohort 2 (C2, CPI refractory) enrolled patients with up to two prior systemic therapies including at least one CPI. Primary endpoint in phase 1b was safety, primary endpoint in phase II was overall response rate (ORR) and secondary endpoint of progression free survival (PFS) and overall survival (OS) and biomarkers evaluation. Results: Fifty-seven patients were enrolled, 42 were in C1 and 15 in C2. One dose limiting toxicity (DLT) of grade 3 neutropenia was noted with G 60 mg/m2. The combination of G 45 mg/m2 on days 1-5 along with D at 1500 mg on day 8, was deemed safe and the recommended phase II dose. Asymptomatic neutropenia was the most common adverse event (AE). Other AEs included thyroid dysfunction, diarrhea, pneumonitis, myalgia, and hepatotoxicity. No treatment-related deaths were reported. The ORR for C1 and C2 were 26% and 7% respectively. The median PFS for C1 and C2 were 18.4 and 3.9 months respectively. Median OS was not reached. Flow cytometry on peripheral blood (PB) collected before treatment demonstrated myeloid-derived suppressor cells (MDSC) to be inversely associated with response, showing the highest levels in progressive disease (PD) and the lowest in partial response (PR). Responders to treatment had the highest expression of IFN γ, IL-17 and RORyt in CD8+ T cells and lower Foxp3 expression in CD4+ T cells compared to non-responders. We observed a significant increase in serum CXCL9/CXCL10 with the study combination (p 0.00003 and p 0.000005 respectively) and this increase correlated with better clinical outcome. Conclusions: The combination of D and G has an acceptable toxicity profile and promising efficacy mainly PFS in CPI naïve ccRCC patients, that is worth further investigation in larger randomized clinical trial. Clinical trial information: NCT03308396 .

Outcomes with immune checkpoint inhibitor (ICI) therapy in patients with FGFR2/3 alterations in advanced urothelial carcinoma (aUC)

478

Background: Erdafitinib is FDA-approved for patients (pts) with advanced urothelial carcinoma (aUC) with FGFR2/3 mutation or fusion and progression after platinum-based chemotherapy. It is postulated that FGFR3-altered aUC may be a “cold tumor” and associated with non-T cell-inflamed phenotype and, thus, may be less responsive to ICI. We hypothesized that pts with aUC that harbor FGFR2/3 alterations would have lower response and shorter survival on ICI. Methods: We performed a retrospective cohort study of pts with aUC treated with ICI and available genomic data in 11 institutions; pts with pure non-UC, treated with combinations or on clinical trial were excluded. Outcomes (overall response rate [ORR], progression free survival [PFS] and overall survival [OS] were compared in pts with and without FGFR2/3 alterations. PFS and OS was compared using Cox proportional hazards. All analyses were performed in the overall population and also categorized by treatment line (1st line [1L] vs salvage [2+L]). Multivariable models were adjusted for an internally developed risk score for 1L and Bellmunt risk score for 2+L; p<0.05 was significant. Results: 310 pts met inclusion criteria; 217 pts, 206 pts, and 204 pts were included in ORR, OS and PFS analyses, respectively. Median follow up time was 37 months [mo]. Overall, median age at ICI initiation was 69, 74% men, 85% White, 27% mixed histology, 24% upper tract, 15% liver metastases, 55% ECOG PS 0-1; 101 pts (33% of total population) had FGFR2 or FGFR3 mutation/fusion. ORR to ICI in pts with FGFR2/3 alteration was 25% (95% CI 15-37%) vs 46% (95% CI 38-55%) in pts without such alterations. PFS was shorter for pts with FGFR2/3 alteration (median [m] PFS 4 mo vs 7 mo without such alterations; HR=1.53 [95% CI 1.09-2.15], p=0.015). However, OS was similar in both groups (mOS 14 mo in both groups; HR=1.09 [95% CI 0.75-1.58], p=0.65). ORR, PFS and OS analyses stratified by ICI treatment line (1L vs 2+L) are shown in the Table. Conclusions: In this multisite retrospective study, the presence of FGFR2/3 alterations was associated with lower ORR and shorter PFS in pts with aUC treated with ICI. Limitations include retrospective nature, lack of randomization and central scan review, selection bias, missing data, and possible residual confounding. Findings suggest that FGFR2/3 alterations may impact response and PFS with ICI and might inform discussion on the optimal sequence of therapies in aUC but need external validation and ideally clinical trial data. [Table: see text]

EVEREST: Everolimus for renal cancer ensuing surgical therapy—A phase III study (SWOG S0931, NCT01120249)

LBA4500

Background: Patients (pts) who undergo resection of renal cell carcinoma (RCC) with curative intent remain at risk for disease relapse. We conducted a phase III, double-blind, placebo (PB)-controlled, intergroup study to determine the effect of adjuvant treatment with the mTOR inhibitor everolimus (EVE) on recurrence-free survival (RFS). Methods: Pts with treatment-naïve, non-metastatic, fully-resected RCC at intermediate high- (pT1 G3-4 N0 to pT3a G1-2 N0) or very high-risk (pT3a G3-4 to pT4 G-any or N+) for recurrence were randomized 1:1 to EVE 10 mg PO daily x 54 weeks or PB within 12 weeks of radical or partial nephrectomy. Randomization was stratified by risk group, histology (clear vs. non-clear cell), and performance status (0 vs. 1). RFS was the primary end point; secondary endpoints included overall survival (OS) and adverse events (AEs). The study was designed to detect an 18% reduction in the risk of RFS with EVE compared to PB, corresponding to an improvement of median RFS from 6.75 (based on E2805 ASSURE) to 8.23 years. Final analysis, using a stratified logrank test, was to occur after 804 total events or by 3/2022, whichever occurred first. Results: Between 4/2011 and 9/2016, 1545 pts were randomized to EVE (n = 775) or PB (n = 770). Overall pt characteristics included: intermediate high-/very high-risk 45%/55%; clear cell/non-clear cell 83%/17%. The DSMC recommended study continuation after each of 4 pre-specified interim analyses. 556 DFS events among 1499 eligible pts occurred by the time of final study analysis on 2/23/2022. The median follow-up was 76 months. RFS was improved with EVE vs. PB (HR 0.85, 95% CI, 0.72 – 1.00; P1-sided= 0.0246), narrowly missing the pre-specified, one-sided significance level of 0.022 which accounted for interim analyses. Median RFS was not reached; the 6-year RFS estimate was 64% for EVE and 61% for PB. RFS improvement with EVE vs. PB was observed in the very high-risk group (HR 0.79, 95% 0.65-0.97; P1-sided= 0.011) but not in the intermediate high-risk group (HR 0.99, 95% CI 0.73-1.35, P1-sided= 0.48) ( P for interaction = 0.22). With 290 deaths, OS was similar between arms (HR 0.90, 95% CI, 0.71 – 1.13; P1-sided= 0.178). Fewer pts completed all 54 weeks of study treatment in the EVE group (45% v 69%). In the EVE group, 37% withdrew due to AEs (vs 5% in PB). Grade 3-4 AEs occurred in 46% of pts treated with EVE and 11% with PB. The most common grade 3-4 AEs were mucositis (14% v 0%), hypertriglyceridemia (11% vs. 2%), and hyperglycemia (5% vs. 0%). Conclusions: Adjuvant EVE improved RFS in RCC pts after nephrectomy, but the nominal significance level was narrowly missed. The RFS improvement was seen despite a high rate of early treatment discontinuation. A 21% improvement in RFS with EVE was observed in pts with very high-risk disease, a group for whom adjuvant therapy may be most relevant. Clinical trial information: NCT01120249.

Piflufolastat F 18-PET/CT in patients with prostate cancer: An analysis of OSPREY (cohorts A and B) standardized uptake value (SUV) results stratified by PSA and Gleason score

5024

Background: The OSPREY clinical trial was a phase 2/3 prospective study of prostate specific membrane antigen (PSMA) PET/CT using piflufolastat F 18. Piflufolastat F 18 (aka 18F-DCFPyL or PyL) is a novel PSMA-targeting radiopharmaceutical approved for imaging of PCa pts both at initial staging and for disease recurrence. Here we describe SUV results by biopsy status, baseline PSA levels, and Gleason score (GS). Methods: Piflufolastat F 18-PET/CT was evaluated in men with NCCN high-risk PCa scheduled to undergo radical prostatectomy with pelvic lymphadenectomy (RP-PLND) (Cohort A) and men with radiologically suspected recurrent/metastatic PCa (Cohort B). A single IV dose of 9 mCi (333 MBq) of piflufolastat F 18 was administered followed by PET/CT acquisition 1-2 hours later. Piflufolastat F 18 uptake in various lesion locations as defined by maximum and peak SUV (SUVmax, SUVpeak) were determined by three blinded, independent central readers for each tissue (e.g., bone, lymph nodes (LN), soft tissue). To measure SUVs, the reader placed a volume of interest (VOI) on each identified lesion. SUVmax was defined as the maximum single-voxel SUV within the VOI. SUVpeak within the VOI was defined as the average SUV within a fixed-sized VOI (1 cm diameter sphere), representing the cluster with the highest average SUV. Results: 345 men underwent piflufolastat F 18-PET/CT. Cohort B (n = 93evaluable) SUVmax and SUVpeak were significantly higher for biopsy positive (+)(one biopsy lesion/pt) when compared to biopsy negative (-) lesions from bone and LN. SUVpeak for biopsied bone and LN (Cohort B) appeared to increase with rising baseline PSA. In high-risk PCa pts, SUVpeak for prostate (Cohort A; n = 252 evaluable) increased with baseline PSA and were highest for GS 9-10 (Table). Conclusions: Piflufolastat F 18-PET/CT uptake was significantly higher in biopsy + lesions and increased with baseline PSA. Prostate SUVpeak was highest for GS 9-10. Clinical trial information: NCT02981368. [Table: see text]

Outcomes with novel combinations in nonclear cell renal cell carcinoma (nccRCC): ORACLE study

4545

Background: Despite recent advances in the treatment of clear cell RCC, there is a paucity of data to guide management of nccRCC due to the heterogeneity and rarity of these tumors. The clinical activity of combination therapies (including IO-IO, IO-VEGF, VEGF-mTOR) in subtypes of advanced nccRCC is unknown. Methods: In this multicenter retrospective analysis, we evaluated the efficacy of combination systemic therapies in patients with nccRCC. Eligible patients included those with nccRCC as determined by local genitourinary pathology review and receipt of one of three combination regimens during any line treatment (IO-IO, IO-VEGF, mTOR-VEGF). The primary endpoint was objective response rate (ORR) assessed by investigator review. Secondary endpoints were progression- free survival (PFS), disease control rate (DCR), and overall survival (OS). Results: Among 128 included patients, median age was 57 years; 66% were male and 65% white. Histologies included papillary (37%), unclassified (33%), chromophobe (16%), translocation (9%), and other (5 %). Among all patients, 69% had prior nephrectomy; 80% were IMDC intermediate/poor risk; 20% had sarcomatoid and/or rhabdoid differentiation, 27% and 29% had liver and bone metastasis respectively and 63% received combination treatment as first line. Comparison of outcomes based on treatment regimen, line of treatment and subtype is shown in the table. Median PFS and OS were longer with IO/IO and IO/VEGF compared to VEGF/ mTOR at 8.5, 9.5 and 3.7 months and 24.4, 18.2 and 15.4 months respectively. Conclusions: Antitumor activity was observed with novel combinations in nccRCC in both frontline and later line setting. Optimal management of nccRCC remains an unmet need and prospective data is warranted to guide treatment selection for this population. [Table: see text]

Temsirolimus (T) in patients (pts) with solid tumors with mTOR mutation: Results from the Targeted Agent and Profiling Utilization Registry (TAPUR) Study

3114

Background: TAPUR is a phase II basket study evaluating anti-tumor activity of commercially available targeted agents in pts with advanced cancers with genomic alterations. Results in a cohort of solid tumor pts with mTOR mutation (mut) treated with T are reported. Methods: Eligible pts had solid tumors, no standard treatment (tx) options, measurable disease, ECOG Performance Status (PS) 0-2, and adequate organ function. Genomic testing was performed in CLIA-certified, CAP-accredited site selected labs. Pts matched to T had various solid tumors with mTOR mut. After antihistamine pre-treatment, 25 mg T was infused over 30-60 minutes weekly until disease progression. Primary endpoint was disease control (DC), defined as complete (CR) or partial (PR) response, or stable disease at 16+ weeks (wks) (SD 16+) (RECIST v1.1). Low accruing histology-specific cohorts with the same genomic alteration and tx were collapsed into a single histology-pooled cohort for this analysis. For histology-pooled cohorts with sample size ≤28, the results are evaluated based on a one-sided exact binomial test with a null DC rate of 15% vs. 35% (α = 0.10 and power=0.86 for N = 26) and one-sided 90% confidence interval (CI). Other efficacy endpoint estimates are presented with two-sided 95% CIs. Secondary endpoints were progression-free survival (PFS), overall survival (OS) and safety. Results: 29 pts with solid tumors (11 histologies) with mTOR mut were enrolled from June 2016 to June 2020. 3 pts were not evaluable (2 pts, no post-baseline tumor eval; 1 pt, no measurable disease) and excluded from efficacy analyses. The Table shows demographics and outcomes. 2 PR and 10 SD16+ were observed for a DC rate of 46% (one-sided 90% CI: 32% to 100%) and an objective response (OR) rate of 8% (95% CI: 1% to 25%); the null hypothesis of a 15% DC rate is rejected (p<0.001). 5/10 pts with SD16+ had CRC or biliary cancer. Of the 2 pts with PR, one had uterine cancer and T1977R mut and the other had head and neck cancer and I1636V mut. The durations of PR were 12.3 and 23.9 wks, respectively, and median duration of SD was 34.5 wks (range: 18.7, 90.0) for pts with SD16+. 8 pts experienced grade 3 or grade 4 AEs or SAEs at least possibly related to T, including acute kidney injury, epistaxis, hyperglycemia, hypertension, hypertriglyceridemia, mucositis, leukopenia, thrombocytopenia, and pneumonitis. Conclusions: Monotherapy T showed evidence of anti-tumor activity in pts with advanced solid tumors with mTOR mut. Additional study is warranted to confirm the efficacy of T in pts with mTOR mut. Clinical trial information: NCT02693535. [Table: see text]

Biomarker-directed therapy in black and white men with metastatic castration-resistant prostate cancer (mCRPC)

5013

Background: Black men have been underrepresented in large-scale molecular prostate cancer (PC) surveys, despite having higher PC incidence and mortality. Since molecular profiling to guide the use of targeted agents is increasingly important in mCRPC, we compared precision medicine data and utilization in a cohort of black and white men with mCRPC. Methods: The PROMISE precision medicine database is an academic collaboration to compile clinical and genomic data from men with PC. All patients have had germline and/or somatic genetic testing performed. Eligibility criteria for this analysis included a diagnosis of mCRPC with available race and biomarker data. The primary outcome was the proportion of non-Hispanic black (NHB) and non-Hispanic white (NHW) men with actionable molecular data, defined as the presence of mismatch repair deficiency (MMRd/MSI-H), homologous recombination repair deficiency (HRRd), tumor mutational burden (TMB) ≥ 10 mut/MB, or AR-V7. Secondary outcomes included the proportion of NHB and NHW men with other alterations, the type and timing of genomic testing performed, and the use of targeted therapy. Results: A total of 962 mCRPC patients (21.2% NHB; 78.8% NHW) met inclusion criteria of 1619 in the overall database. Median age (NHB/NHW) was 61/63; 77.5/68.8% had Gleason 8-10; 52.5/56.7% presented with de novo metastatic disease (33.8/29.9% LN, 36.2/32.2% bone and 8.3/6.1% viscera). The median time from diagnosis to first molecular result was 56.3 mo for NHB v 58.7 mo for NHW (p = 0.45). Use of blood-based molecular testing was more common in NHB men (48.7% v 36.4%, p < 0.001). Overall, 32.8% of NHB men harbored actionable molecular data compared to 30.3% of NHW men (Table). MMRd/MSI-H was more common in NHB men (9.1 v 4.9%, p = 0.04). Other than PTEN (12.7/23.8% NHB/NHW, p = 0.0001), no significant differences were seen in the 15 most frequently mutated genes, including TP53, AR, CDK12, RB1, and PIK3CA. Tumor suppressor co-mutations (PTEN/TP53/RB1) were found in 13.1% of NHB and 18.0% NHW (p = 0.13). Delivery of targeted therapy was reported in 19.6% of NHB and 23.7% of NHW men (p = 0.25) after a median of 2 CRPC lines. Median OS from development of mCRPC was 41.5 mo (95% CI, 34.7-51.3) and 44.7 mo (95% CI, 41.1-51.5) for NHB and NHW men, respectively (p = 0.14). Conclusions: In a real-world mCRPC molecular profiling cohort, we found similar overall rates of actionable molecular alterations in NHB and NHW men, but higher rates of MMRd/MSI-H and lower frequency of PTEN alterations in NHB men. We did not find differences in delivery of targeted therapy. [Table: see text]

Focal radiation with pulsed systemic therapy of abiraterone, androgen deprivation therapy (ADT), olaparib towards castration-sensitive oligometastatic prostate cancer (FAALCON Trial)

TPS5113

Background: Molecular imaging (i.e. PSMA directed agents) identifies metastatic prostate cancer at an earlier disease state than conventional imaging resulting in a new clinical entity within metastatic hormone-sensitive prostate cancer (mHSPC): molecular positive HSPC (mpHSPC). Historically, patients in this category with prior local therapy would have been classified as having a biochemical recurrence only, and observation was routine. Approaches to mpHSPC include observation or the use of focal and/or systemic therapies. Focal radiation for mpHSPC may delay the need for systemic therapy, yet many patients require further focal or systemic treatment. Androgen deprivation therapy (ADT) with abiraterone (abi) benefits men with high-risk localized disease and standard mHSPC. mpHSPC hypothetically resides somewhere between these two disease states. Finally, the inhibition of poly(ADP-ribose) polymerase (PARP) with olaparib plus abi shows promise in metastatic castration resistant prostate, suggesting this approach may be worthy of testing in earlier disease states. Methods: FAALCON is a single-site, phase 2 clinical trial testing olaparib with abi, ADT and radiation therapy in oligometastatic mpHSPC. Oligometastatic mpHSPC is defined as up to 5 radiation treatment sites (5 cm maximum size each) and must encompass all visible disease on the molecular scan. Patients must have had their prostate previously treated. The primary endpoint is the percentage of patients without treatment failure 24 months from study start. Treatment failure is defined as one of the following: new or progressive metastases on CT/MRI, new lesions on bone scan without alternate explanation, clinical progression, or a PSA doubling time under 6 months with an absolute final PSA over 1.5 ng/mL. Additional radiation therapy is deemed progression. Select secondary endpoints include time to any subsequent therapy, and percentage of patients with undetectable PSA with a recovered testosterone at multiple timepoints. Correlative work will analyze quality of life and prior prostatic tissue. ADT and abi (1000 mg daily) are given for 6 months, and radiation is completed by day 40. Olaparib (300 mg PO twice daily) is started 2 weeks after radiation completes and continues for the remaining ̃5 months. After therapy completion, patients are monitored by PSA q3 months with imaging based on predetermined PSA cutoffs. Molecular imaging (PSMA-PET) may be offered on study. Historical disease control at 24 months is estimated at 40% from prior molecular guided radiation studies and intermittent ADT. With 80% power and a one-sided 5% type-I error, we can detect a hazard ratio of 0.5 (80% control rate) at 24 months with 26 patients. To account for dropout, 29 patients will be accrued. Clinical trial information: NCT04748042.

Targeting resistant prostate cancer, with or without DNA repair defects, using the combination of ceralasertib (ATR inhibitor) and olaparib (the TRAP trial)

88

Background: Men with metastatic, castration resistant prostate cancer (mCRPC) harboring DNA repair defects (̃20%) achieve a radiographic progression free survival of 7.4 months with PARP inhibitors (PARPi). Preclinical studies combining a PARPi (olaparib) and DNA damage checkpoint inhibitor (ATR inhibitor, ceralasertib) show synergy, providing the rationale to test this combination in men with mCRPC, including where single agent olaparib has been shown to be active. Methods: Two cohorts were accrued to a trial combining ceralasertib with olaparib in men a) with or b) without DNA repair defects. All patients progressed on ≥1 prior mCRPC therapy with no prior PARPi or platinum chemotherapy. The primary endpoint was disease response (confirmed PSA decline ≥50% and/or RECIST response), while disease progression was defined per Prostate Cancer Working Group 3 definition. Each cohort is analyzed independently for disease endpoints, while both groups were combined for toxicity assessments. Results: The 12 person DNA repair-deficient (DRDef) cohort allowed patients with germline BRCA2 loss (n = 4), somatic BRCA2 loss (n = 1) and ATM loss (n = 1 germline, n = 5 somatic and n = 1 somatic with unknown germline). 35 men without BRCA2/BRCA1 or ATM genomic loss were accrued to the DNA repair-proficient (DRPro) cohort. These men had next-generation sequencing (NGS) on contemporary biopsies (prior to enrolment without intervening therapy, 12), prior NGS on metastatic tissue (10), prior NGS on primary prostatic tissue (n = 3), or cell-free analyses (5). Five patients have incomplete cell-free analyses. At data cutoff (October 2021), in the DRDef cohort, the response rate by confirmed ≥50% PSA decline was 4/10 (40%) including 3 of 4 BRCA2 patients, and another is awaiting sufficient follow up; 1 of 6 ATM-deficient patients responded and another is awaiting sufficient follow up. All 4 DRDef responders remain on therapy (median of 8 months). For patients in the DRPro cohort who have completed therapy and response assessment (n = 21), 3 responded, one with a duration of 12 months, two with 6 months. An updated analysis will be presented. Conclusions: This analysis suggests potential activity of the doublet for DRDef (BRCA2 mainly) and DRPro mCRPC. Ongoing biomarker analysis (e.g. ATM IHC, contemporaneous cell-free DNA analysis rather than archived tissue) may help guide selection of patients most likely to benefit. Clinical trial information: NCT03787680.

SWOG S1314: A randomized phase II study of co-expression extrapolation (COXEN) with neoadjuvant chemotherapy for localized, muscle-invasive bladder cancer with overall survival follow up

536

Background: This trial evaluated COXEN, a gene expression model, as a predictive biomarker in muscle-invasive bladder cancer (BC) patients randomized to Gemcitabine-Cisplatin (GC) or dose-dense Methotrexate-Vinblastine-Adriamycin/doxorubicin-Cisplatin (ddMVAC). Primary results correlating COXEN with pathologic response at surgery have been reported. This secondary analysis includes progression-free (PFS) and overall survival (OS). Methods: Eligibility included Stage cT2-T4a N0 M0, urothelial BC (mixed histology allowed), ≥ 5 mm of viable tumor, cisplatin eligible, with plan for cystectomy. 237 patients were randomized between ddMVAC, given every 14 days for 4 cycles, and GC, given every 21 days for 4 cycles. Cox regression was used to evaluate COXEN score or treatment arm association with PFS and OS, adjusting for stratification factors (stage and PS). Results: 167 patients were included in the primary COXEN analysis all having either at least 3 cycles of chemo and surgery within 100 days of last chemo or having progressed while receiving chemo. The COXEN scores were not significantly prognostic for OS or PFS in their respective arms; the COXEN GC score was a significant predictor for OS in pooled arms. OS and PFS data are shown for both scores in the table. In the intent to treat analysis (n=227), there was no significant difference in OS or PFS for ddMVAC versus GC (for OS, HR =0.87, 95% CI 0.54-1.40), p = 0.57); for PFS (HR= 0.76 95% CI 0.58-1.01, p = 0.055). Association of path response with OS will be presented. Conclusions: The COXEN GC score may be prognostic of survival in those receiving platinum-based neoadjuvant treatment. The randomized, prospective design provides estimates of OS and PFS for GC and ddMVAC that appear comparable, but this phase II trial is underpowered for definitive comparisons. The prospective data and correlative samples from S1314 will allow for further assessment of COXEN and other RNA and DNA based predictive and prognostic biomarkers. Clinical trial information: NCT02177695. [Table: see text]

ABLE: Phase 2, single-arm, two-stage study of nabpaclitaxel with anti-PD1/PDL1 in advanced urothelial cancer

502

Background: Anti-PD/PDL1 immune checkpoint inhibitor monotherapy is standard in select PDL1 expressing advanced urothelial cancer (aUC) and platinum-refractory aUC. Nab-paclitaxel (NAB) previously showed encouraging activity in platinum-refractory aUC. We conducted a single-arm trial of the combination of NAB and pembrolizumab in platinum-refractory or cisplatin-ineligible aUC. Methods: Eligible patients (pts) had RECIST 1.1 measurable urothelial cancer, grade ≤1 neuropathy, and ECOG PS 0-2. Study therapy consisted of NAB at starting dose of 125 mg/m2 IV on days 1 and 8 and pembrolizumab 200 mg IV on day 1 in 21-day cycles until progression, intolerable toxicity, death, or consent withdrawal. Continuing NAB after 6 cycles was optional. NAB starting dose was reduced to 100 mg/m2 after planned interim analysis on the first 17 subjects. Primary endpoint was overall response rate (ORR) by RECIST 1.1. Secondary endpoints included safety/toxicity, progression free survival (PFS), overall survival, complete response proportion, duration of response (DOR), and duration of therapy (DOT). Results: Between 2/2018 and 4/2021, 36 response evaluable pts were enrolled; 11 of upper tract origin, 32 men, mean age 71.5 years (range 52 – 88), 25 pure urothelial, 15 platinum-refractory, 21 cisplatin-ineligible by Galsky criteria, and ECOG PS was 0, 1 or 2 in 9, 20, and 7 pts, respectively. Unconfirmed best ORR was 58.3% (95% CI: 42-74) including 3 CR and 18 PR, confirmed ORR 50% (18/36); 31/36 pts experienced some tumor shrinkage. Median DOR was 19 weeks (95% CI: 15.6-34.8), and median PFS 5.4 months (95% CI: 4.6-7.9). Pts received a median of 6 cycles (range 1-14) with median DOT 4.2 months (range 0.6-9.6). Grade ≥3 adverse events (AE) occurred in 25 pts including fatigue (n = 6), anemia (n = 6), peripheral neuropathy (n = 3), and oral mucositis (n = 3); 6 discontinued treatment due to AEs. Ten pts had immune mediated AEs including 1 with encephalitis. Archival tumor NGS revealed TMB ≥10 in 5/21 available. Conclusions: The combination of NAB and pembrolizumab exhibited promising activity in advanced urothelial cancer with no unexpected toxicity. Clinical trial information: NCT03240016.

Prognostic value and therapeutic implications of an integrative molecular subtype and immune content classifier in localized muscle-invasive bladder cancer

530

Background: Localized muscle-invasive bladder cancer (MIBC) exhibits heterogeneous molecular features and outcomes, with a 5-year mortality rate of approximately 30%. Immune checkpoint blockade (ICB) has the potential to improve oncological outcomes but molecular tools are needed to identify those most likely to benefit. Here, we integrate transcriptomically derived tumor immune microenvironment (TIME) data with molecular subtypes to create a novel integrative classifier with prognostic and therapeutic implications. Methods: RNAseq data from patients with localized muscle-invasive bladder cancer (MIBC) from the Cancer Genome Atlas BLCA (TCGA-BLCA) project was utilized (n = 187). CIBERSORT was used for immune cell deconvolution, and unsupervised hierarchical clustering divided the cohort based on similar immune profiles. Consensus molecular clustering information for the cohort was obtained from Kamoun et al. Overall survival (OS) of each cluster were analyzed. The tumor immune dysfunction and exclusion (TIDE) tool, which uses a genomic signature validated on immunotherapy treated melanoma patients to model tumor immune evasion, was then used to predict response to ICB. Results: In the TCGA-BLCA cohort, there were two distinct clusters enriched with macrophages, CL1-M0Hi (n = 18) and CL5-M2Hi (n = 35). Compared to the rest of the cohort, these two macrophage enriched clusters combined exhibited a decreased OS (33.1 mo vs. NR, p = 0.01). TIDE tool predicted ICB response was lowest in CL1 (6/18, 33%; p = 0.09), CL5 (12/35, 34%; p = 0.02), and the Ba/Sq molecular cluster (16/57, 28%; p = 1.3x10-5). Patients designated as CL1 or CL5 by immune clustering and Ba/Sq by molecular consensus were combined into a subgroup (n = 20). Compared to the rest of the cohort, this Ba/Sq_MacrophageHi subgroup had a higher body mass index (31.0 vs. 25.8 BMI, p = 0.0004), more whites (95% vs. 64%, p = 0.03), and had a higher stage (80% Stage III/IV vs. 20% Stage I/II, p = 0.05). The Ba/Sq_MacrophageHi cluster demonstrated higher PD-L1 expression (mean Z score 0.15 vs. -0.09; p = 0.008), there was a higher degree of T cell exclusion (mean Z score 0.16 vs. -0.06; p = 0.003) and cancer-associated fibroblasts (mean Z score 0.03 vs. -0.02; p = 3.4x10-5). Overall, the predicted response to ICB by TIDE in the Ba/Sq_MacrophageHi was lower (OR 0.15, 0.03-0.55 p = 0.002) and OS was significantly shorter (median 16.7 mos vs. 54.9 mo, p = 0.04). Conclusions: We demonstrated the prognostic significance of the Basal/Squamous subtype with macrophage enrichment in patients with localized MIBC. Pending further prospective validation, this sub-population may be less amenable to ICB treatment.

Characterizing IMDC prognostic groups in contemporary first-line combination therapies for metastatic renal cell carcinoma (mRCC)

308

Background: The combination of immuno-oncology agents (IO) ipilimumab and nivolumab (IPI-NIVO) and combinations of IO with vascular endothelial growth factor targeted therapies (IOVE) have demonstrated efficacy in clinical trials for the first-line treatment of mRCC. This study seeks to establish real-world clinical benchmarks based on the International mRCC Database Consortium (IMDC) criteria using vascular endothelial growth factor targeted therapy (VEGF-TT) treated patients for context. Methods: The IMDC database (IMDConline.com) was used to identify patients with mRCC who received first-line IPI-NIVO, IOVE (axitinib/pembrolizumab, lenvatinib/pembrolizumab, cabozantinib/nivolumab, or axitinib/avelumab) and VEGF-TT (sunitinib or pazopanib) from 2002-2021. The primary endpoint was overall survival (OS) and was calculated from time of initiation of first-line therapy to death or last follow up. Log-rank tests were conducted to compare favorable, intermediate, and poor risk OS outcomes within treatment groups. Overall response rates (ORR) and complete response (CR) rates were calculated based on physician assessment of best clinical response. Results: In total, 692 patients received IPI-NIVO, 244 received IOVE, and 7152 received VEGF-TT. Baseline characteristics for IPI-NIVO, IOVE, and VEGF-TT, respectively, were as follows: median age (interquartile range) 63 (56-69), 64 (57-70), and 63 (56-70); male 72%, 74%, and 72% (p=0.74); non-clear cell histology 15%, 10%, and 13% (p=0.15); sarcomatoid features 24%, 15%, and 13% (p<0.0001); brain metastasis 8%, 4%, and 8% (p=0.04); liver metastasis 18%, 14%, and 18% (p=0.17); underwent nephrectomy 61%, 79% and 80% (p<0.0001). OS and ORR are reported in the table. P-values (log rank) for OS between risk groups were significant for IPI-NIVO (p<0.0001), IOVE (p=0.0005), and VEGF-TT (p<0.0001). Conclusions: These findings provide real-world survival and response benchmarks for contemporary first-line mRCC treatments and could be helpful for patient counselling. In addition, these findings mirror the efficacy of combination therapies established in clinical trials against VEGF-TT monotherapy. IMDC criteria continue to risk stratify patients in these novel combination therapies.[Table: see text]

First-line therapy for metastatic renal cell carcinoma with pancreatic metastases: Results from the International Metastatic Renal Cell Carcinoma Database Consortium (IMDC)

317

Background: Metastatic renal cell carcinoma (mRCC) with pancreatic metastases (PM) is characterised by heightened angiogenesis, which is associated with improved outcomes with vascular endothelial growth factor (VEGF) inhibitors. We aimed to compare the efficacy of first-line (1L) ipilimumab/nivolumab (IOIO) vs. anti-PD(L)1/anti-VEGF (IOVE) vs. VEGF monotherapy (VE) in mRCC patients with and without PM. Methods: We performed a retrospective analysis of patients with and without PM, using the IMDC. Sites of metastases were captured at initiation of 1L. Patients with PM could also have metastases at other sites. We studied overall survival (OS) from start of 1L therapy using Cox regression, adjusted for IMDC risk groups. Kaplan Meier survival curves were generated. Results: 543/7,634 (7%) patients had PM. Patients with PM in the overall population had improved OS compared to those without, 56 vs 25.6 months respectively (HR 0.63, 95% CI 0.55-0.73, p<0.0001). When examining the effect of PM within 1L options, those treated with IOVE exhibited a longer OS if PM were present vs absent, median not reached vs 45 months respectively (HR 0.41, 95% CI 0.18-0.93 p=0.03). This association was also seen in patients with treated with 1L VE, in those with PM vs absent, median 53.1 vs 25.1 months respectively (HR 0.65, 95% CI 0.55-0.76, p <0.0001). Contrastingly there was no difference in median OS of patients with or without PM in patients receiving IOIO, 41.4 vs 44.4 months respectively (HR 0.86, 95% CI 0.48-1.56, p=0.62). Comparing the outcomes between 1L therapies in patients with PM the median OS of IOVE vs VE was not reached vs 53.1 months respectively (HR 0.37, 95% CI 0.16-0.83 p=0.02). Conversely, upfront VE and IOIO had a similar median OS of 53.1 vs 41.4 months respectively (HR 0.81, 95% CI 0.45-1.47 p=0.49). We were unable to find any difference in OS between those treated with IOVE vs IOIO, median not reached vs 41.4 months respectively (HR 0.52 95%, CI 0.19-1.45, p=0.21), but the low event rate limited this interpretation. Conclusions: We found that the presence of PM leads to an indolent biological behavior and was associated with improved outcomes when 1L therapy included a VE component. PM patients had comparable OS outcomes on 1L VE and 1L IOIO therapy, but improved OS when treated with 1L IOVE. Anti-angiogenic therapy may be necessary to optimize outcomes in PM and this warrants prospective evaluation. [Table: see text]

Implications of androgen receptor (AR) alterations identified by genomic testing of tissue and blood from advanced prostate cancer (aPC) patients (pts)

138

Background: AR alterations such as ligand binding domain mutations and amplification evolve under the selective pressure of testosterone suppression and AR targeted agents (ARTA) such as abiraterone or enzalutamide, but their relevance to ARTA treatment outcomes remain unclear. Methods: PROMISE is a multi-institutional retrospective clinical-genomic database inclusive of aPC pts who had tissue and/or blood based genomic testing by commercially available CLIA-certified platforms. We analyzed men who received second generation ARTA and stratified patients according to genomic testing timing (pre-/post-ARTA), castration resistance, type of AR alteration, and PSA decline ≥50% on first ARTA. Time to progression (TTP) from first ARTA initiation was estimated using the Kaplan-Meier method and differences between subgroups defined by AR alteration status were assessed using the log-rank test. Results: 854 pts who received ARTA and had tissue-based (n = 600) or blood-based (n = 335) genomic testing were included. Median age was 62 (range, 33-93). Pre- and post-ARTA genomic testing was available in 387 and 467 pts, respectively. AR alterations were identified in 16% (61/387) of pre-ARTA and 48% (226/467) of post-ARTA pts with AR amplifications in 10% (38/387) and 35% (161/467) of the pts, respectively. 15/52 pts who had pre- and post-ARTA testing developed a new AR alteration. In pre-ARTA cohort; castration status, median TTP, and PSA response for 1st ARTA according to alteration status are summarized in the table. In the post-ARTA group, the most common AR mutations were L702H (53%), followed by T878A (33%); whereas, in the pre-ARTA group, the H875Y (26%) mutation was most common. AR mutations in post-ARTA group were seen at similar rates regardless of prior docetaxel exposure (14.3% vs 18.0%, p = 0.46) and following first abiraterone vs enzalutamide/apalutamide exposure (48.6% vs 48.3%, p = 1.0). Conclusions: AR mutations, unlike amplifications, were associated with shorter TTP on abiraterone. Genomic testing should be considered before second line ARTA.[Table: see text]

Association of TMB and PD-L1 with efficacy of first-line pembrolizumab (pembro) or pembro + chemotherapy (chemo) versus chemo in patients (pts) with advanced urothelial carcinoma (UC) from KEYNOTE-361

540

Background: The 3-arm, open-label, phase 3 KEYNOTE-361 study (NCT02853305) evaluated first-line pembro ± chemo vs chemo in advanced UC regardless of PD-L1 status. The trial did not meet its primary end points of superior PFS and OS with pembro + chemo vs chemo and thus analysis of pembro monotherapy (mono) vs chemo was exploratory. We explored the association of TMB status and PD-L1 combined positive score (CPS) with clinical outcomes in KEYNOTE-361. Methods: In pts with TMB and/or PD-L1 data, the association between TMB (via whole exome sequencing) and PD-L1 (via PD-L1 IHC 22C3 pharmDx) and clinical outcomes (ORR, PFS, and OS) was evaluated. In each treatment arm, the hypotheses regarding the associations were evaluated using logistic regression (ORR) and Cox proportional hazards regression (PFS; OS), and 1-sided (pembro; pembro + chemo) and 2-sided (chemo) P values were calculated; significance was prespecified at α = 0.05 without multiplicity adjustment. Clinical utility was assessed using prespecified cutoffs of 175 mut/exome (TMB) and CPS 10 (PD-L1). Clinical data cutoff was April 29, 2020. Results: 820/993 pts (82.6%) had evaluable TMB data (pembro, 252; pembro + chemo, 282; chemo, 286). TMB (log10) was significantly positively associated with ORR, PFS, and OS for pembro ( P < 0.001, < 0.001, and 0.007, respectively) and PFS and OS for pembro + chemo ( P= 0.007 and 0.010, respectively). The area under the receiver operating characteristics (AUROC) curve (95% CI) for discriminating response was 0.64 (0.56-0.71) for pembro, 0.53 (0.46-0.60) for pembro + chemo, and 0.52 (0.45-0.59) for chemo. Efficacy by TMB cutoff is reported in the Table. All 993 pts had PD-L1 data (pembro, 302; pembro + chemo, 349; chemo, 342). PD-L1 was significantly positively associated with PFS for pembro ( P= 0.006) and ORR for pembro + chemo ( P= 0.042) but not chemo. Efficacy by PD-L1 CPS is reported in the Table. Conclusions: Strong associations were observed between TMB and all 3 clinical outcomes (ORR, PFS, and OS) with pembro mono in the first-line setting and a reduced association was observed between TMB and clinical outcomes with pembro + chemo. No consistent associations were observed between PD-L1 and clinical outcomes with pembro mono or pembro + chemo. Clinical trial information: NCT02853305. [Table: see text]

Post hoc pooled analysis of first-line (1L) pembrolizumab (pembro) for advanced urothelial carcinoma (UC): Outcomes by response at week nine in KEYNOTE-052 and KEYNOTE-361

519

Background: Pembro is a 1L treatment for cisplatin-ineligible pts with UC. This post hoc landmark analysis evaluated clinical outcomes by response at 9 wk to 1L pembro monotherapy in pts with advanced/unresectable or metastatic UC from the single-arm phase 2 KEYNOTE-052 (NCT02335424) and the randomized phase 3 KEYNOTE-361 (NCT02853305) trials. Methods: Cisplatin-ineligible pts with advanced UC were enrolled in KEYNOTE-052 and received pembro (200 mg Q3W for ≤2 y). Platinum-eligible pts with advanced UC who had not previously received systemic chemotherapy (chemo) were enrolled in KEYNOTE-361 and randomly assigned 1:1:1 to receive pembro (200 mg Q3W for ≤2 y), pembro + chemo (1000 mg/m2 gemcitabine on d1 and d8 + cisplatin [70 mg/m2] or carboplatin [AUC 5] on d1 of each 3-wk cycle), or chemo. The primary analysis group included pembro monotherapy–treated pts; the sensitivity analysis group included pembro monotherapy–treated pts from KEYNOTE-052 and the choice of carboplatin subpopulation of pembro monotherapy–treated pts from KEYNOTE-361. Landmark analyses of OS by pts with CR, PR, SD, or PD per RECIST v1.1 by BICR at first imaging assessment (wk 9) were pooled for the ITT populations. Duration of CR/PR/SD and OS were estimated using the Kaplan-Meier method. Data cutoffs were Sep 26, 2020 (KEYNOTE-052) and Apr 29, 2020 (KEYNOTE-361). Results: The primary analysis group included 681 pembro-treated pts (KEYNOTE-052, N = 374; KEYNOTE-361, N = 307); the sensitivity analysis group included 544 pembro-treated pts (KEYNOTE-052, N = 374; KEYNOTE-361, N = 170). Median time from randomization to cutoff was 51.9 mo (range, 22.0-65.3) and 53.7 mo (range, 22.0-65.3) for the primary and sensitivity analysis groups, respectively. Twenty-five pts (4.6%) had CR and 135 (24.6%) had PR (primary group); 17 pts (3.9%) had CR and 105 (24.1%) had PR (sensitivity group). Median DOR was 25.9 mo for pts with CR/PR at wk 9; pts with CR/PR or SD at wk 9 had longer OS than pts with PD at wk 9 (Table). Conclusions: In this post hoc analysis, pts with advanced UC in KEYNOTE-052 and KEYNOTE-361 with CR/PR at wk 9 had better clinical outcomes with pembro monotherapy than pts with SD or PD; 1L pembro monotherapy continues to show efficacy in advanced UC. Clinical trial information: NCT02335424 and NCT02853305. [Table: see text]

DNA damaging therapies in patients (pts) with prostate cancer (PC) and pathogenic alterations in homologous recombination repair (HRR) genes

129

Background: Pathogenic HRR gene mutations may confer sensitivity to PARP inhibitors (PARPi) and/or platinum chemotherapy (chemo). While pts harboring mutations in BRCA1/2 appear to benefit from these DNA damaging therapeutics, outcomes data for those with non- BRCA1/2 mutations are less robust. We evaluated outcomes in men with HRR gene-mutated PC who received treatment with PARPi and/or platinum-based chemo stratified by type of HRR alteration. Methods: Retrospective data from the PROMISE Consortium was utilized (PMID: 34363009). PC pts with pathogenic HRR mutations who received PARPi and/or platinum-based chemo were included. Differences in PSA progression-free survival (PFS), clinical/radiographic PFS (rPFS), and overall survival (OS) between those with BRCA1/ 2 mutations (Cohort A) and those with mutations in HRR genes that do not directly interact with the BRCA complex (Cohort B: ATM, CDK12, CHEK1, CHEK2, FANCL) were evaluated. We also evaluated outcomes in pts with HRR gene mutations known to interact with the BRCA complex aside from BRCA1/2 (Cohort C: RAD51B/C/D, RAD54L2, BARD1, GEN1, PALB2, FANCA, BRIP1). Results: Of 361 pts identified with HRR gene alterations, 89 received PARPi and 70 received platinum-based chemo. Prior therapy and metastatic disease sites were similar between cohorts. PSA PFS, rPFS, and OS were significantly improved in Cohort A vs. Cohort B with PARPi but not platinum-based chemo (Table). Sample size in cohort C was too small to allow for statistical comparison, although PSA PFS, PFS and OS were reasonably long. Conclusions: PC pts with BRCA1/2 mutations had improved outcomes to PARPi compared to those with mutations in HRR genes not directly interacting with the BRCA complex. Platinum-based chemo appeared effective regardless of which HRR gene was affected. [Table: see text]

A phase II trial of abemaciclib (abema) and atezolizumab (atezo) in unselected and CDK12-loss metastatic castration-resistant prostate cancer (mCRPC)

TPS213

Background: Alterations in the cell cycle signaling pathway are common in mCRPC and may contribute to resistance to AR-targeted therapies. Inhibitors of cyclin-dependent kinases 4 and 6 (CDK4/6i) have revolutionized the therapeutic landscape in ER+ breast cancer and have demonstrated robust anti-tumor activity in multiple pre-clinical mCRPC models such as enzalutamide-resistant cell lines, including those with the androgen-receptor splice variant 7 (AR-V7). Pre-clinical synergy has also been seen in multiple studies of CDK4/6i and anti-programmed death 1 (PD-1) or PD-ligand-1 (PD-L1). Additionally, loss of function alterations of CDK12, found in 5-7% of mCRPC, may confer vulnerability to anti-PD-L1 agents. Methods: This multi-center study will enroll 54 unselected mCRPC patients (pts), randomized 1:1 to abema (arm A) or abema + atezo (arm B); and 21 pts with known loss of function mutations in CDK12 (arm C) treated with atezo (n = 5) or abema + atezo (n = 16). All pts will undergo on-treatment (6-week) tumor biopsy. Treatment will be continued until disease progression and crossover is prohibited. Key eligibility criteria are age ≥ 18 years, ECOG PS 0-1, biopsy-proven prostate adenocarcinoma, progressive metastatic disease per Prostate Cancer Working Group 3 (PCWG3), progression/intolerance to ≥ 1 novel antiandrogen in hormone-sensitive or CRPC setting, ineligible for docetaxel/cabazitaxel (progression within 12 months of taxane, pt refusal, investigator discretion), no uncontrolled comorbidity or history of pneumonitis/ILD. Arms A & B will use two stage design for co-primary endpoints of progression-free survival at 6 months using PCWG3 (6m-PFS) and objective response rate (ORR). If ≥ 1/12 pts meet either co-primary endpoint, 2nd stage will open to enroll 15 more pts in that arm. Treatment will be deemed to have meaningful clinical activity (MCA) if ≥ 6/27 meet 6m-PFS or ≥ 5/27 have an ORR. This will provide 86% power for 6m-PFS (34% vs. 12%) and 85% power for ORR (30% vs. 10%) at a one-sided α = 0.08. For MCA in arm C, 16 patients treated with abema+atezo will provide 80-85% power for 6m-PFS (34% vs. 12%) at a one-sided α = 0.05 using a one-sample log-rank test. Primary safety endpoint is the incidence of dose-limiting toxicities in pts receiving abema+atezo. Key secondary endpoints are clinical benefit rate (ORR + stable disease), duration of response and overall survival in arms A and B, and safety events in all arms. Primary exploratory endpoint is comparison of tumoral FoxP3+/CD8+ ratio in pts treated with abema vs. abema + atezo. Additional exploratory endpoints will evaluate association between response and genomic alterations identified from tissue or circulating tumor-derived exosomes. Enrollment began in July 2021 and projected enrollment goal is 3 years (NCT04751929). Clinical trial information: NCT04751929.

First-line pembrolizumab in advanced urothelial carcinoma: Clinical parameters associated with efficacy in the phase 2 KEYNOTE-052 and phase 3 KEYNOTE-361 trials

521

Background: First-line treatment with pembrolizumab (pembro) monotherapy has shown durable clinical activity in selected patients (pts) with advanced/unresectable or metastatic urothelial carcinoma (UC). In a pooled population of pts with advanced UC from the single-arm phase 2 KEYNOTE-052 (NCT02335424) and the randomized, open-label, phase 3 KEYNOTE-361 (NCT02853305) studies, this exploratory analysis evaluated the relationship between baseline characteristics and clinical outcomes of first-line pembro monotherapy. Methods: Cisplatin-ineligible pts with advanced UC were enrolled in KEYNOTE-052 and chemotherapy-naive pts with advanced UC were enrolled in KEYNOTE-361. For analysis of predictive factors for ORR and OS in pembro-treated pts, the purposeful selection method was used to build the multivariable logistic regression model (ORR) and multivariable Cox model (OS), beginning with a univariable analysis of each independent variable. Any variable in the univariate model with P < 0.10 was a candidate for the multivariate model. The stepwise selection method was used to select the variables in the final model. Significance of the final model was set at P < 0.05. Data cutoff dates were September 26, 2020 (KEYNOTE-052) and April 29, 2020 (KEYNOTE-361). Results: This pooled analysis included 681 pts treated with pembro monotherapy (KEYNOTE-052, N = 374; KEYNOTE-361, N = 307 [170 were cisplatin ineligible]). Median follow-up was 51.9 mo (range, 22.0-65.3). ORR was 29.4% (95% CI, 26.0-32.9; 69 CRs, 131 PRs), and median DOR was 33.2 mo (range, 1.4+ to 60.7+). Median OS was 12.5 mo (95% CI, 11.0-14.6). By multivariate analysis, independent factors significantly associated with higher ORR were PD-L1 status (combined positive score [CPS] ≥10 vs CPS < 10; odds ratio [OR], 1.90 [95% CI, 1.33-2.71]; P = 0.0004), site of metastasis (lymph node only vs visceral disease; OR, 1.66 [95% CI, 1.06-2.59]; P = 0.0265), liver involvement (absent vs present; OR, 1.75 [95% CI, 1.06-2.89]; P = 0.0294), and baseline hemoglobin level ≥10 vs < 10 g/dL; OR, 2.17 [95% CI, 1.09-4.31]; P = 0.0276). Multivariate analysis of OS is displayed in the Table. Conclusions: This exploratory multivariate analysis identified numerous factors, including PD-L1–positive status (CPS ≥10), lymph node only metastasis, and lower ECOG PS score, associated with improved clinical outcomes in pts with advanced UC treated with first-line pembro monotherapy. Clinical trial information: NCT02335424 and NCT02853305. [Table: see text]

Phase 2 trial of immunotherapy in tumors with CDK12 inactivation (IMPACT): Results from cohort A of patients (pts) with metastatic castration resistant prostate cancer (mCRPC) receiving dual immune checkpoint inhibition (ICI)

103

Background: Prostate cancer with CDK12 inactivation represents a distinct subtype in mCRPC, tumors are characterized by excessive tandem duplications, genomic instability, gene fusion-caused putative neoantigens and increased tumor T cell infiltration. Retrospective experiences with ICI in CDK12 inactivation CRPC pts reported PSA and radiographic responses. We conducted a prospective multi-site clinical trial of ipilimumab and nivolumab in CDK12 inactivation or mutated cancers. Herein, we report our findings in the completed cohort A of men with mCPRC. Methods: Eligible pts had mCRPC (ongoing androgen deprivation therapy with serum testosterone £ 50 ng/dL) and putative CDK12 inactivation of function aberrations on any commercial or institutional CLIA/CAP approved next generation sequencing assay. Archival tumor tissue was requested for correlative biomarker analysis. Pts received nivolumab 3 mg/kg IV and ipilimumab 1 mg/kg IV q3 weeks for up to 4 cycles, followed by maintenance nivolumab at 480 mg IV q4 weeks until disease progression, intolerable toxicity, or consent withdrawal. The primary endpoint was PSA response, defined as a greater than or equal to 50% decline in PSA from baseline. Secondary endpoints included safety/toxicity, secondary efficacy measures including QoL and overall survival. Exploratory objectives included baseline tumor whole exome analysis and changes in circulating immune profiles with therapy. Results: As of data cut-off in Aug 2021, 28 mCRPC pts enrolled in Cohort A; median ECOG PS was 1 (0-2 range), 22/28 had Gleason 8-10 cancer, mean baseline PSA at study entry was 231 ng/dL, all pts had received ≥1 prior oral androgen signaling inhibitor and ≥1 cytotoxic chemotherapy. Unconfirmed PSA ≥30% decline was seen in 6/28 pts (21.4%) and PSA ≥50% decline in 4/28 pts (14.2%). Grade ≥3 possible/probable/definite adverse events were noted in 7/28 (25%) and SAEs in 10/28 pts (35.7%). Six pts (21.4%) experienced a rapid PSA increase by ≥ 10-fold over baseline. Conclusions: Combination immunotherapy was reasonably tolerated in this heavily pre-treated population and was associated with unconfirmed PSA responses in a subset of pts. Ongoing correlative analyses could explain responses mechanistically. Enrollment in Cohort B of non-prostate cancers and Cohort C of nivolumab monotherapy in prostate cancer are still ongoing. Clinical trial information: NCT03570619.

Piflufolastat F 18-PET/CT in prostate cancer patients: An analysis of OSPREY (Cohorts A and B) standardized uptake value (SUV) results stratified by PSA and gleason score

35

Background: The OSPREY clinical trial was a phase 2/3 prospective study of prostate specific membrane antigen (PSMA) PET/CT using piflufolastat F 18. Piflufolastat F 18 (aka 18F-DCFPyL or PyL) is a novel PSMA-targeting radiopharmaceutical approved for imaging of PCa pts both at initial staging and for disease recurrence. Here we describe SUV results by biopsy status, baseline PSA levels, and Gleason score (GS). Methods: Piflufolastat F 18 -PET/CT was evaluated in men with NCCN high-risk PCa scheduled to undergo radical prostatectomy with pelvic lymphadenectomy (RP-PLND) (Cohort A) and men with radiologically suspected recurrent/metastatic PCa (Cohort B). A single IV dose of 9 mCi (333 MBq) of piflufolastat F 18 was administered followed by PET/CT acquisition 1-2 hours later. Piflufolastat F 18 uptake in various lesion locations as defined by maximum and peak SUV (SUVmax, SUVpeak) were determined by three blinded, independent central readers for each tissue (e.g., bone, lymph nodes (LN), soft tissue). To measure SUVs, the reader placed a volume of interest (VOI) on each identified lesion. SUVmax was defined as the maximum single-voxel SUV within the VOI. SUVpeak within the VOI was defined as the average SUV within a fixed-sized VOI (1 cm diameter sphere), representing the cluster with the highest average SUV. Results: 345 men underwent piflufolastat F 18-PET/CT. Cohort B (n = 93 evaluable) SUVmax and SUVpeak were significantly higher for biopsy positive (+) (one biopsy lesion/pt) when compared to biopsy negative (-) lesions from bone and LN. SUVpeak for biopsied bone and LN (Cohort B) appeared to increase with rising baseline PSA. In high-risk PCa pts, SUVpeak for prostate (Cohort A; n = 252 evaluable) increased with baseline PSA and were highest for GS 9-10 (Table). Conclusions: Piflufolastat F 18-PET/CT uptake was significantly higher in biopsy + lesions and increased with baseline PSA. Prostate SUVpeak was highest for GS 9-10. Clinical trial information: NCT02981368. [Table: see text]

Differential responses to taxanes and PARP inhibitors (PARPi) in ATM- versus BRCA2-mutated metastatic castrate-resistant prostate cancer (mCRPC) patients (pts)

5040

Background: PARPi have shown promise in mCRPC pts with mutations in DNA repair, but ATM- and BRCA2-altered pts may respond differently to PARPi. We hypothesized that differences may also exist for taxane therapy, aiding in treatment sequencing decisions. Methods: mCRPC pts (N = 137) with deleterious ATM or BRCA2 mutations who received taxanes, PARPi, or both were identified from 8 US academic centers. Demographic, treatment, and survival data were collected. Kaplan-Meier analyses were performed for time-to-treatment-discontinuation (TTD), as well as overall survival (OS), from time of first taxane or PARPi therapy. Cox hazard ratio (HR) regression analyses were performed, adjusting for Gleason sum (≤7 vs. 8-10). For OS, receipt of subsequent therapies following first taxane or PARPi was also included as a covariate. Results: 50 ATM- and 87 BRCA2-mutated pts were identified. 40/50 (80%) of ATM-mutated pts received taxane only or taxane prior to PARPi, while 10/50 (20%) received PARPi only or PARPi prior to taxane. ATM-mutated pts showed a trend towards longer TTD when taxane was given first vs PARPi given first (P = 0.08, adjusted HR for taxane treatment 0.50 [95% CI: 0.24–1.08]). Considering all pts who received taxane first, ATM-mutated pts had longer TTD than BRCA2-mutated pts who received taxane first ( P= 0.04, adjusted HR for ATM 0.61 [CI: 0.37–0.99]). Among ATM-mutated pts, OS was longer in those receiving taxane first ( P= 0.06, adjusted HR for taxane treatment 0.33 [CI: 0.10–1.05]). Among BRCA2-mutated pts, 43/87 (49%) received taxane first and 44/87 (51%) received PARPi first. BRCA2-mutated pts had longer TTD when PARPi was given first vs taxane given first ( P< 0.0001, adjusted HR for PARPi treatment 0.32 [CI: 0.19–0.56]). Considering all pts who received PARPi first, BRCA2-mutated pts also had longer TTD than ATM-mutated pts who received PARPi first ( P= 0.0031, adjusted HR for BRCA2 0.29 [CI: 0.12–0.66]). There was no significant OS difference in BRCA2-mutated pts regarding which treatment was given first ( P= 0.63, adjusted HR for PARPi treatment 1.18 [CI: 0.59–2.35]). Conclusions: Our data in ATM- and BRCA2-mutated mCRPC pts suggests a trend towards improved clinical outcomes when taxanes are used prior to PARPi in ATM-mutated pts, while the reverse sequence appears to be better for BRCA2-mutated pts.[Table: see text]

Pembrolizumab (pembro) in combination with gemcitabine (Gem) and concurrent hypofractionated radiation therapy (RT) as bladder sparing treatment for muscle-invasive urothelial cancer of the bladder (MIBC): A multicenter phase 2 trial

4504

Background: Trimodality bladder preservation therapy (TMT) is a standard treatment option for clinically localized MIBC with curative intent. Pembro has shown activity in MIBC in the neoadjuvant setting and may combine well with TMT to improve outcomes. This trial evaluated the safety and efficacy of pembro added to TMT in MIBC. Methods: This multicenter phase 2 trial included pts with cT2 – T4aN0M0 MIBC who declined or were ineligible for cystectomy (RC), ECOG PS 0/1, eGFR > 30 cc/min, and no contraindications to pelvic RT or pembro. No perioperative chemotx for MIBC was permitted. Pts received pembro 200 mg x 1 followed 2-3 weeks by maximal TURBT and then whole bladder RT (52 Gy/20 fx; IMRT preferred) with twice wkly gem 27 mg/m2 and pembro Q3 wks x 3 treatments. 12 wks post-RT, CT/MR AP, TUR of tumor bed and cytology were performed to document response. Up to 6 pts were enrolled to a safety cohort (SC) followed by 48 pts in efficacy cohort (EC). The primary endpt is 2-yr bladder-intact disease-free survival (BIDFS: first of MIBC or regional nodal recurrence, distant metastases, or death) assessed by serial cysto/cytology and CT/MRI. EC had 85% power to detect a 20% absolute improvement in 2-yr BIDFS rate over 60% historical rate (RTOG Pooled analysis; Mak JCO 2014). Key secondary endpts were safety, 12 wks CR rate, metastases-free survival and overall survival. Tumor tissue was collected at study entry, maximal TURBT and post-treatment TUR of tumor bed with serial PBMCs for correlative analyses. Results: From 5/2016 to 10/2020, 54 pts (6 SC, 48 EC; 72% M) enrolled at 5 centers; Median age 67 (65-89) for SC and 74 (51-97) for EC. C-stage (74% cT2, 22% cT3, and 4% cT4). 39 (72%) declined RC. All 6 pts in SC and 42/48 (88%) of EC pts completed all study therapy; 1/48 (2%), 2/48 (4%), and 4/48 (8%) discontinued RT/Gem, Gem or Pembro, respectively, most often due to toxicity. As of 1/2021 (median F/U 40.9 mos (38.6-50.8) SC and 11.7 mos (0.6 – 32.2) EC), no recurrences in SC, and 12/48 EC pts had any recurrence (6 NMIBC, 0 MIBC, 2 regional and 4 distant). The estimated 1 yr BIDFS rate is 77% (95% CI: 0.60-0.87). 12 wks CR rate was 100% in SC and 83% for EC (1 PR, 3 NR, 1 Progression, 11 NE; 2 still on active study). In the EC, 35% of pts had a Gr ≥3 TEAE (Gr 3 events included UTI 8%, diarrhea 4%, colitis 4%, bladder pain/obstruction 4%, neutropenia 2%, thrombocytopenia 2%). Notable Pembro Gr ≥3 TRAE included 3 pts (6%) Gr 3 GI toxicity and 1 pt Gr 4 colonic perforation. 1 patient died due to fungemia, unrelated to study therapy. Conclusions: Pembro added to hypofractionated RT and twice weekly gem was well-tolerated with promising efficacy in this early analysis. Pembro-related toxicity was consistent with prior monotherapy trials. Selected correlative analyses from serially collected blood and tissue specimens will be presented. Clinical trial information: NCT02621151.

Outcomes with novel combinations in non-clear cell renal cell carcinoma(nccRCC): ORACLE study

4580

Background: Despite advances in the treatment of clear cell RCC, there is a paucity of data to guide management of nccRCC due to the heterogeneity and rarity of these tumors. The clinical activity of new combination therapies (including immunotherapy (IO), anti-vascular endothelial growth factor inhibitors (VEGF), and mammalian target of rapamycin (mTOR) inhibitors) in metastatic nccRCC is not known. Methods: In this multicenter retrospective analysis, we explored the efficacy of combination systemic therapies in patients with nccRCC. Baseline and follow-up demographic, clinical, treatment, and radiographic data were collected. The primary endpoint was objective response rate (ORR) assessed by investigator review. Secondary endpoints include progression- free survival (PFS), disease control rate (DCR), median duration of response (DOR), overall survival (OS), and biomarker correlates. Results: Among 66 included patients, median age was 59 yr; 60% were male and 62% white. Histologies included papillary (38%), chromophobe (17%), unclassified (24%), translocation (12%), and other (9 %). Sarcomatoid and/or rhabdoid differentiation was present in 18%, 70% had prior nephrectomy, 86% were IMDC intermediate/poor risk, 29% and 32% had liver and bone metastasis respectively. 67% received combination treatment in the first line. Comparison of outcomes based on treatment regimen is shown in the table. Conclusions: Antitumor activity was observed with novel combinations in nccRCC which warrants further prospective studies. Response rates and survival with combination therapy in this dataset remain inferior to rates seen in clear cell RCC.[Table: see text]

Immune checkpoint inhibitors (ICI) in advanced sarcomatoid renal cell carcinoma (sRCC): A multicenter study

4568

Background: Advanced sRCC is an aggressive disease with limited responsiveness to chemotherapy and VEGF-targeted therapies. Subgroup analyses from randomized trials showed improved outcomes with ICI, though sample sizes were relatively small. Methods: We conducted a multi-institutional retrospective analysis of consecutive patients (pts) who had RCC with any sarcomatoid component and received systemic therapy for advanced disease. The pts were classified into ICI+ and ICI- groups (gp) based on whether they had received ICI in any treatment line. Overall survival (OS) was measured from the initiation of first systemic therapy. Time to ICI failure (TIF) was defined as the interval from initiation of ICI to subsequent therapy or death. Survival distributions were estimated using the Kaplan-Meier method. Association between covariates and survival was analyzed using multivariate Cox regression. Two-tailed P < 0.05 was considered statistically significant. Results: 203 pts from 6 US academic cancer centers met the inclusion criteria – 155 in ICI+ gp and 48 in ICI- gp. Overall, 137 (67%) pts were male and 181 (89%) were white; median age at mRCC diagnosis was 59.7 (IQR 52.4-67.7) years; 129 (63%) pts presented de novo with distant metastases, 154 (76%) had clear cell (CC) histology, and 182 (90%) had intermediate/poor risk by IMDC criteria. ICI+ had a higher proportion of purely CC tumors (81% vs 64%, P =.02); other demographic and clinical features were similar between the two gps. After a median follow-up of 48.1 (95% CI 40.7-55.5) months (mos), median OS and response rates were significantly higher in the ICI+ gp (Table). OS benefit, compared to ICI-, was maintained in pts who received ICI in ≥ second line (39.6 vs 7.6 mos, HR 0.33, 95% CI 0.22-0.51, log-rank P <.001). TIF was comparable between pts treated with ICI upfront vs in ≥ second line (6.0 vs 5.3 mos, HR 1.27, 95% CI 0.87-1.85, P =.21). On multivariate analysis, ICI- (HR 2.50, 95% CI 1.61-3.88, P <.001), non-CC histology (HR 3.14, 95% CI 1.98-5.00, P <.001) and sarcomatoid component ≥20% (HR 1.92, 95% CI 1.28-2.90, P =.002) were predictive of all-cause mortality. Among pts with non-CC or mixed histology (n=45), ICI+ had higher OS (18.0 vs 5.5 mos, HR 0.20, 95% CI 0.09-0.44, P <.001) and ORR (44% vs 12%, P =.03), compared to ICI-. Conclusions: Treatment with ICI led to markedly higher survival and response rates in advanced sRCC. OS benefit was maintained with ICI in the second line and beyond. Significant benefit was also noted among pts with non-CC or mixed histology sRCC.[Table: see text]

A prospective phase 2/3 study of PSMA-targeted 18F-DCFPyL-PET/CT in patients (pts) with prostate cancer (PCa) (OSPREY): A sub-analysis of disease staging changes in PCa pts with recurrence or metastases on conventional imaging

e17003

Background: Conventional imaging and bone scintigraphy are suboptimal modalities for identifying PCa. PSMA-based imaging is highly promising for PCa detection. 18F-DCFPyL is a novel PSMA-targeted radiopharmaceutical for positron emission tomography (PET) that may be useful in staging of PCa. The diagnostic performance, detection rate, and potential impact of 18F-DCFPyL on staging of pts with high-risk PCa have been previously reported. Here we report on the impact of 18F-DCFPyL on staging of pts with PCa recurrence or metastases on conventional imaging. Methods: 18F-DCFPyL-PET/CT was evaluated in 117 men with radiologic evidence of local recurrence or metastatic disease on baseline anatomical imaging (CT, MRI) or whole-body bone scintigraphy and in whom at least one lesion was deemed amenable to biopsy. A single dose of 9 mCi (333 MBq) of 18F-DCFPyL was administered via intravenous injection, followed by PET/CT acquisition 1 to 2 hours thereafter. Based on TNM staging: prostatic (T), pelvic LN (N), extra-pelvic LN (M1a), bone (M1b) and other visceral organs/soft tissue (M1c), 18F-DCFPyL-PET/CT detection rates including lesion counts were systematically analyzed. Three central, blinded, and independent readers evaluated the 18F-DCFPyL scans. Results: In this study, 82 (70%) patients had baseline radiographic M1 stage disease (14 patients with M1a, 50 patients with M1b, 18 patients with M1c) and 33 (28%) patients were M0 stage at baseline by central conventional imaging review; two patients were unevaluable. 18F-DCFPyL-PET/CT up-staged 58% (19/33) of pts from M0 to M1, of whom 91% (10/11) who underwent an extra-pelvic biopsy were confirmed to have M1 disease by pathology, including 9 patients with M1b and 1 patient with M1a. Of the patients who were staged M1 at baseline, 18F-DCFPyL-PET/CT upstaged 16% (10/64; M1a to M1b or M1c: n = 4; M1b to M1c: n = 6) of pts to a higher M1 sub-stage and down-staged 22% (18/82) to M0. Conclusions: 18F-DCFPyL-PET/CT identified M1 disease in the majority of patients examined who otherwise had locoregional disease. These data suggest that 18F-DCFPyL-PET/CT may be a useful tool in properly staging men with both metastatic and nonmetastatic relapsed disease, which could lead to superior treatment paradigms than currently exist using conventional imaging. Clinical trial information: NCT02981368.

Response and outcomes to immune checkpoint inhibitors (ICI) in advanced urothelial cancer (aUC) based on prior intravesical BCG

4537

Background: Little is known regarding response and outcomes to ICI for patients (pts) with aUC who were previously treated with BCG for non-muscle invasive bladder cancer. We hypothesized that prior intravesical BCG would not be associated with changes in objective response or survival in pts with aUC treated with ICI. Methods: We performed a retrospective cohort study across 25 institutions. Demographic, intravesical BCG history, treatment and outcomes data were collected for pts with aUC who received ICI. Pts with aUC treated with ICIs were included, pts with pure non-UC, those treated with combination or on clinical trials, pts with multiple ICI treatment lines and those with upper tract UC were excluded. Pts were stratified to prior exposure versus no exposure to BCG. We compared overall response rate (ORR) using logistic regression; and progression-free survival (PFS) and overall survival (OS) using Kaplan-Meier and Cox proportional hazards. All analyses were performed in the overall population and further stratified by treatment line (first-line [1L] vs salvage [2+L]) and multivariable models. The stratified analysis was also adjusted for an internally developed risk score for 1L and Bellmunt risk score for 2+L; p<0.05 was significant. Results: 1026 aUC pts treated with ICI were identified; 614 pts, 617 pts, and 641 pts were included in ORR, OS and PFS analyses, respectively. Overall, mean age at CPI initiation was 70, 76% were men, 70% were current or former smokers, 75% White, 29% with mixed histology, and 24% had prior exposure to BCG. ORR to ICI in pts with or without prior exposure to BCG was similar, 27% and 28% respectively (OR=0.93 [95% CI 0.61-1.42], p=0.73). Median OS (mOS) for pts with vs without prior BCG exposure was 9 vs 10 mo (HR=1.13 [95% CI 0.88-1.44], p=0.35). Median PFS (mPFS) was 4 months (mo) in both groups (HR=1.02 [95% CI 0.82-1.27], p=0.83). ORR, PFS and OS analyses stratified by ICI treatment line (1L vs 2+L) are listed in the table. Conclusions: In this multi-institutional retrospective analysis, prior intravesical BCG was not associated with objective response or survival in pts with aUC treated with ICI. Limitations of this study include retrospective nature, lack of randomization and possible confounding, but it does provide important preliminary data that selection for ICI treatment should not be impacted by prior exposure to BCG. Further clinical and molecular biomarker exploration is needed to refine patient selection for ICI in aUC.[Table: see text]

Impact of subsequent therapy on survival in KEYNOTE-361: Pembrolizumab (pembro) plus chemotherapy (chemo) or pembro alone versus chemo as first-line therapy for advanced urothelial carcinoma (UC)

439

Background: The phase III KEYNOTE-361 study examined the efficacy and safety of 1L pembro + chemo or pembro alone vs chemo for pts with advanced UC. The PFS and OS benefit of pembro + chemo vs chemo did not reach statistical significance; no further formal tesing was done. We present an exploratory analysis of OS by subsequent therapy in KEYNOTE-361 (NCT02853305) to assess how 1L and 2L therapy selection affected survival outcomes; no formal comparisons were conducted. Methods: OS was estimated for pts by whether they received subsequent therapy, and by whether subsequent therapy included an anti–PD-(L)1 agent. Results: 351 pts were randomized to pembro + chemo, 307 pts to pembro, and 352 pts to chemo. As of Apr 29, 2020, the median (range) time from randomization to data cutoff was 31.7 (22.0-42.3) mo. 124/351 pts (35%) in the pembro + chemo arm, 126/307 pts (41%) in the pembro arm, and 215/352 pts (61%) in the chemo arm received any subsequent therapy. Similar rates of subsequent therapy (pembro + chemo: 32%; pembro: 43%; chemo: 59%) were observed for pts who experienced progressive disease (PD) by blinded independent central review (BICR). A higher rate of pts (169/352 [48%]) in the chemo arm received subsequent anti–PD-(L)1 therapy than in either the pembro + chemo arm (23/351 [7%]) or pembro arm (14/307 [5%]). Due to the small pt numbers, pts in the pembro + chemo or pembro arms who received subsequent anti−PD-(L)1 were not considered further. This analysis included all pts who received 2L therapy (465/1010 pts [46%]); the rate of 2L therapy was similar in pts with PD by BICR (274/615 [45%]). Chemo agents alone or in combination, specifically carboplatin, cisplatin, docetaxel, doxorubicin, gemcitabine, and paclitaxel, were the most commonly received subsequent therapies for pts who did not receive anti–PD-(L)1 in 2L. Pts who received 1L chemo followed by subsequent anti–PD-(L)1 had longer mOS (19.1 mo [95% CI 16.2-22.2]) than pts with 1L pembro followed by 2L therapy not including an anti−PD-(L)1 agent (16.0 mo [95% CI 11.8-19.2]) (Table). Conclusions: In this exploratory analysis, favorable survival outcomes were observed for pts who received 1L chemo followed by anti–PD-(L)1 compared with pts who received 1L pembro followed by 2L therapy not including an anti–PD-(L)1 agent. These data underline the continued importance of immunotherapy as 2L therapy for advanced UC. Clinical trial information: NCT02853305 . Research Sponsor: Merck & Co., Inc[Table: see text]

Phase Ib/II study of durvalumab and guadecitabine in advanced kidney cancer Big Ten Cancer Research Consortium BTCRC GU16-043

328

Background: Anti-PD1/PDL1 immune checkpoint inhibition (CPI) is active in advanced clear cell RCC, but not all patients benefit. Preclinical studies with the combination of hypomethylating agents and CPI resulted in reversal of immune evasion and tumor regression. We examined the combination of the hypomethylating agent guadecitabine (subcutaneously on Days 1-5), with the anti-PDL1 antibody durvalumab (intravenously at flat dose of 1500 mg on Day 8) in 28 day cycles in advanced RCC in a single arm trial. Methods: In the phase Ib portion (n=6; presented previously), guadecitabine dosing of 45 mg/m2/day was selected as maximum tolerated dose. For the phase II portion of Cohort 1 (36 pts with no prior CPIs), eligible patients had metastatic RCC with clear cell component, ECOG PS of 0-1, and measurable disease by RECIST 1.1. We present pooled efficacy and toxicity data for the 42 CPI-naive pts from the phase Ib and phase II portions. An exploratory Cohort 2 (N=16) consisting of CPI-refractory pts is enrolling. Results: Of the 42 pts, 71% were men, median age was 67 years, ECOG PS was 0 in 57%, IMDC risk group was intermediate in 83% and poor in 17%, and histology was mixed in 21%. At a median follow-up of 20.1 m, best RECIST 1.1 response was PR in 9 pts (22%); SD in 25 pts (61%); PD in 7 pts (17%); and non-evaluable in 1 pt. Response categories were identical by irRECIST. Clinical benefit defined as either PR or SD ≥6 months was seen in 66%. Median OS had not been reached and median PFS was 17 m. Treatment was generally well tolerated with asymptomatic neutropenia the most frequent AE attributed to guadecitabine (38.1%), and asymptomatic lipase elevation the most common AE from durvalumab (11.9%). Grade 4 AEs were noted in 50.0% pts, grade 3 59.5%. Immune-mediated AEs were generally mild (all ≤ grade 3), included pruritus (14.3%), rash (14.3%), asymptomatic amylase or lipase elevations (16.7%), hypothyroidism (11.9%), diarrhea (16.7%), dyspnea (16.7%), pneumonitis (4.8%), myalgia (4.8%), and transaminitis (9.6%). Laboratory peripheral blood profiling (done at baseline, C1D8, C2D8) was associated on univariate unadjusted analysis at baseline with response in two major PBMC subsets - MDSCs (negative) and ILCs (positive). Further functional analysis revealed that increased expression of IL-22 in both CD4 and CD8 positive T cells positively correlated with response. Associations were noted for toxicity with IL-22 expressed by CD8-CD4- T cells, and CTLs T-bet level. Baseline archival tumor tissue next generation sequencing results will be presented. Conclusions: Guadecitabine in combination with durvalumab was well tolerated and had reasonable activity in first-line advanced ccRCC. MDSCs and regulatory T lymphocytes decreased in responders, increased Th17 subpopulations of T cells were associated with immune-mediated toxicities. Further study of this combination in CPI-refractory RCC pts is ongoing. Clinical trial information: NCT03308396 .

Analysis of PFS2 by subsequent therapy in KEYNOTE-361: Pembrolizumab (pembro) plus chemotherapy (chemo) or pembro alone versus chemo as 1L therapy for advanced urothelial carcinoma (UC)

448

Background: 1L pembro + chemo did not show statistically superior PFS and OS vs chemo for pts with advanced UC in the phase III KEYNOTE-361 study; OS for pembro vs chemo was not formally tested. We analyzed PFS2 (time from randomization to progressive disease [PD] on first subsequent therapy, or death from any cause, whichever occurs first) by study treatment and subsequent therapy in KEYNOTE-361 (NCT02853305) to determine the effects, if any, of therapy sequence on PFS2. Methods: PFS2 was estimated for pts in each treatment arm, who received any subsequent therapy including any anti–PD-(L)1, any therapy other than anti–PD-(L)1, or no therapy. These were exploratory analyses; no formal comparisons were done. Results: 1010 pts were randomized: 351 pts to receive pembro + chemo, 307 to pembro, and 352 to chemo. As of Apr 29, 2020, the median (range) time from randomization to data cutoff was 31.7 (22.0-42.3) mo. Subsequent therapy was received by 124/351 (35%), 126/307 (41%), and 215/352 (61%) pts in the pembro + chemo, pembro, and chemo arms, respectively. Subsequent anti–PD-(L)1 therapy was received by 169/352 (48%) pts in the chemo arm vs 23/351 (7%) in the pembro + chemo arm and 14/307 (5%) in the pembro arm. Of pts in the pembro arm who received subsequent therapy, >90% received 2L cisplatin-based or carboplatin-based treatment. Median (m) PFS2 (95% CI) for all pts by treatment arm was 14.1 mo (12.6-16.2) with pembro + chemo, 10.9 mo (9.5-12.9) with pembro, and 10.4 mo (9.8-11.2) with chemo. Across treatment arms, pts in the pembro + chemo arm had the longest mPFS2 with any subsequent therapy (14.5 mo [95% CI 13.1-16.6]) (Table). Pts in the pembro arm who received no subsequent therapy had a longer mPFS2 (12.9 mo [95% CI 8.1-17.9]) vs pts in the chemo arm who received no subsequent therapy (9.4 mo [95% CI 7.6-10.6]). Finally, pts treated with 1L pembro in the trial followed by 2L therapy other than anti−PD-(L)1 had comparable mPFS2 (10.2 mo [95% CI 8.6-12.1]) to pts treated with 1L chemo in the trial followed by 2L anti−PD-(L)1 (11.1 mo [95% CI 10.2-12.9]). Conclusions: In this exploratory analysis, treatment sequence of chemo followed by anti−PD-(L)1 upon PD vs anti–PD-(L)1 followed by chemo upon PD did not appear to impact mPFS2. Among pts who did not receive 2L therapy, 1L pembro appeared to be associated with longer mPFS2 than chemo, potentially driven by long-term responders to pembro. Clinical trial information: NCT02853305 . [Table: see text]

Biomarker-based phase II study of sapanisertib (TAK-228), an mTORC1/2 inhibitor in patients with refractory metastatic renal cell carcinoma (mRCC)

306

Background: Approved rapalogs inhibit mTORC1 and have limited activity in mRCC, possibly due to compensatory feedback loops. Sapanisertib addresses the incomplete inhibition of the mTOR pathway through targeting of both mTORC1 and mTORC2 with antitumour activity demonstrated in patients with mRCC. In this multicenter, single arm phase II trial, we evaluated the efficacy of sapanisertib in patients with mRCC progressing on standard therapies (NCT03097328). Methods: Eligible mRCC patients had an ECOG performance status of 0-2 and had progressed on standard therapies. Prior therapy with rapalogs (everolimus, temsirolimus) and variant RCC histologies were permitted. Patients had a baseline biopsy and received treatment with sapanisertib 30 mg by mouth weekly until unacceptable toxicity or disease progression. The primary endpoint was overall response rate (ORR) by RECIST 1.1. Tissue biomarkers of mTOR pathway activation were explored. Results: We enrolled 38 mRCC patients (clear cell = 28; variant histology = 10) between August 2017 and November 2019. The majority had intermediate (76%) or poor risk (11%) by IMDC criteria. Twenty (53%) had received ≥ 3 lines of therapy; 13 (34%) patients received prior rapalogs. Median follow-up was 10.4 months (range 1-27.4) and median duration of therapy was 1.6 (range 0.3-13.8) months. ORR by central review was 2 of 38 (5.3% 90%CI: 1%-15.6%). 31.6% of all patients and 30.7% of those with prior rapalog exposure had some tumor shrinkage during course of treatment. Median progression free survival (PFS) was 2.5 months (95% CI 1.8,3.7). Twelve patients (32%) developed treatment-related grade 3 adverse events (AEs) with no grade 4 or 5 toxicity reported; 6 patients (16%) required dose reduction and 4 (11%) discontinued therapy for AEs. Oncopanel tumor sequencing identified alterations in the mTOR pathway in 6 of 29 patients ( MTOR n = 2, PTEN n = 3, TSC1 n = 1.) Reduced PTEN expression by immunohistochemistry was seen in 7 of 19 patients. There was no association between mTOR pathway mutations or PTEN loss and response to sapanisertib. Conclusions: In this study we demonstrate minimal activity of sapanisertib in patients with treatment refractory mRCC with no clear benefit among patients with mTOR/PTEN pathway alterations. Additional treatment strategies are needed for patients with refractory mRCC.

A prospective phase II/III study of PSMA-targeted 18F-DCFPyL-PET/CT in patients (pts) with prostate cancer (PCa) (OSPREY): A subanalysis of disease staging changes in PCa pts with recurrence or metastases on conventional imaging

32

Background: Conventional imaging and bone scintigraphy are suboptimal modalities for identifying PCa. PSMA-based imaging is highly promising for PCa detection. 18F-DCFPyL is a novel PSMA-targeted radiopharmaceutical for positron emission tomography (PET) that may be useful in staging of PCa. The diagnostic performance, detection rate, and potential impact of 18F-DCFPyL on staging of pts with high- risk PCa have been previously reported. Here we report on the impact of 18F-DCFPyL on staging of pts with PCa recurrence or metastases on conventional imaging. Methods: 18F-DCFPyL-PET/CT was evaluated in 117 men with radiologic evidence of local recurrence or metastatic disease on baseline anatomical imaging (CT, MRI) or whole-body bone scintigraphy and in whom at least one lesion was deemed amenable to biopsy. A single dose of 9 mCi (333 MBq) of 18F-DCFPyL was administered via intravenous injection, followed by PET/CT acquisition 1 to 2 hours thereafter. Based on TNM staging: prostatic (T), pelvic LN (N), extra-pelvic LN (M1a), bone (M1b) and other visceral organs/soft tissue (M1c), 18F-DCFPyL-PET/CT detection rates including lesion counts were systematically analyzed. Three central, blinded, and independent readers evaluated the 18F-DCFPyL scans. Results: In this study, 82 (70%) patients had baseline radiographic M1 stage disease (14 patients with M1a, 50 patients with M1b, 18 patients with M1c) and 33 (28%) patients were M0 stage at baseline by central conventional imaging review; two patients were unevaluable. 18F-DCFPyL-PET/CT up-staged 58% (19/33) of pts from M0 to M1, of whom 91% (10/11) who underwent an extra-pelvic biopsy were confirmed to have M1 disease by pathology, including 9 patients with M1b and 1 patient with M1a. Of the patients who were staged M1 at baseline, 18F-DCFPyL-PET/CT upstaged 16% (10/64; M1a to M1b or M1c: n = 4; M1b to M1c: n = 6) of pts to a higher M1 sub-stage and down-staged 22% (18/82) to M0. Conclusions: 18F-DCFPyL-PET/CT identified M1 disease in the majority of patients examined who otherwise had locoregional disease. These data suggest that 18F-DCFPyL-PET/CT may be a useful tool in properly staging men with both metastatic and nonmetastatic relapsed disease, which could lead to superior treatment paradigms than currently exist using conventional imaging. Clinical trial information: NCT02981368.

1L pembrolizumab (pembro) versus chemotherapy (chemo) for choice-of-carboplatin patients with advanced urothelial carcinoma (UC) in KEYNOTE-361

450

Background: 1L pembro is approved in advanced UC for cisplatin-ineligible pts with PD-L1 combined positive score (CPS) ≥10 and any platinum-ineligible pts regardless of CPS in the United States based on single-arm trial data. In the phase III KEYNOTE-361 study, 1L pembro + chemo did not statistically significantly improve PFS or OS vs chemo for pts with advanced UC; formal testing of 1L pembro vs chemo was not performed. We present an exploratory analysis of outcomes with pembro vs chemo for choice-of-carboplatin (carbo) pts in KEYNOTE-361 (NCT02853305). Methods: At randomization, choice of platinum agent (cisplatin or carbo) plus gemcitabine for each pt was selected based on investigator’s assessment of cisplatin ineligibility. ORR/DOR per RECIST v1.1 by blinded independent central review and OS were determined for all pts selected for carbo (“choice-of-carbo”) and also choice-of-carbo pts with CPS ≥10. Risk difference assessment for select AEs for pembro vs chemo was conducted in choice-of-carbo pts who received ≥1 dose study treatment. Results: As of Apr 29, 2020, the median (range) time from randomization to data cutoff in the full study cohort was 31.7 (22.0-42.3) mo. At randomization, renal impairment was the most common reason for choice of carbo by investigators (36% of all pts). 170 choice-of-carbo pts were randomized to the pembro arm, and 196 choice-of-carbo pts to the chemo arm. Median OS in this subgroup was 14.6 mo with pembro vs 12.3 mo with chemo (HR 0.83 [95% CI 0.65-1.06]). 18-mo OS rate was 42% with pembro vs 40% with chemo. ORR to pembro vs chemo was 27.6% vs 41.8%. Median (range) DOR with pembro vs chemo was not reached (NR) (3.2+-36.1+ mo) vs 6.3 (1.8+-33.8+) mo. 84/170 (49%) and 89/196 (45%) choice-of-carbo pts in the pembro and chemo arms, respectively, had CPS ≥10. In this subgroup, median OS was 15.6 mo with pembro vs 13.5 mo with chemo (HR 0.82 [95% CI 0.57-1.17]). 18-mo OS rate was 44% with pembro vs 43% with chemo. ORR to pembro vs chemo was 29.8% vs 46.1%. Median (range) DOR with pembro vs chemo was NR (4.2-36.1+ mo) vs 8.3 (2.1+-33.8+) mo. Among treated pts (N=166 for pembro, N=190 for chemo), 112 pts (68%) in the pembro arm and 163 pts (86%) in the chemo arm had grade 3-5 AEs of any cause. Pembro was associated with a higher risk of pruritus, while chemo was associated with a higher risk of decreased white blood cell, neutrophil, and platelet counts, nausea, thrombocytopenia, neutropenia, and anemia. Conclusions: Due to the trial design, this subset was not statistically tested and is exploratory. Median OS and 18-mo OS rates did not appear markedly different in the two arms; some parameters such as DOR favored pembro, although longer follow-up is needed to determine median DOR for pembro. The PD-L1 CPS ≥10 did not clearly enrich for responders to pembro in choice-of-carbo pts. Pembro was associated with a lower rate of grade 3-5 AEs of any cause than chemo. Clinical trial information: NCT02853305.

Efficacy of enfortumab vedotin in advanced urothelial cancer: Retrospective analysis of the Urothelial Cancer Network to Investigate Therapeutic Experiences (UNITE) Study

443

Background: Enfortumab vedotin (EV) is an antibody-drug conjugate targeting Nectin-4, which is FDA approved for patients (pts) with treatment-refractory advanced urothelial cancer (aUC). The activity of EV in pt subsets of interest such as those with distinct histological variants has not been well defined. Methods: A retrospective study of pts with aUC treated with ≥1 dose of EV as standard of care (SOC) or on a clinical trial (if trial results already reported) at 12 US sites was undertaken. Objective response rate (ORR) was investigator-assessed for pts with at least one post-baseline scan or clear evidence of clinical progression. ORR was compared across subsets of interest using proportion test. Results: A total of 184 patients with aUC were included; median age at diagnosis 70, 20% women and 60% with definitive surgery. Most common primary sites included bladder (70%) and upper tract (28%). Majority of pts (72%) had pure urothelial histology (UH) per local review, but 26% had at least a component of variant histology (VH), most commonly squamous (14%), micropapillary (8%) or plasmacytoid (3%). EV was given as monotherapy in 84% and as SOC in 58%; and 81% had ≥ 1 prior treatment in the metastatic (met) setting. ECOG PS was ≥2 in 15%; 37% had baseline neuropathy, 15% diabetes and 9% had GFR≤30. At median follow-up of 37.0 (IQR: 20.5-60.2) months from initial diagnosis, median time from met diagnosis to EV start was 11.7 (IQR: 4.3 – 20.5) months. Median duration of EV was 5.5 (IQR: 1.4 – 6.7) months, and 84% of pts were evaluable for response. ORR for evaluable pts was 53% (8% CR, 45% PR); 25% had SD and 21% PD. Median PFS and OS were not yet reached. At data cutoff in 9/2020, 55% had stopped EV (36% due to PD, 19% intolerance) and 65% were alive. Comparison of ORR in subgroups of interest for 127 evaluable pts treated with EV monotherapy is shown in the table below. Notably, among 31 pts with FGFR3 alterations, 26 were evaluable and ORR was 46%. Conclusions: In a large, retrospective, multi-institutional cohort, responses to EV were observed across a broad range of aUC pts, including pts with variant histology component, FGFR3 alterations and also in populations previously excluded from clinical trials such as pts with GFR<30 and significant baseline comorbidities. No significant differences in ORR were demonstrated for patient subsets of interest. [Table: see text]

Sunitinib versus cabozantinib, crizotinib or savolitinib in metastatic papillary renal cell carcinoma (pRCC): Results from the randomized phase II SWOG 1500 study

270

Background: MET signaling is a key molecular driver in pRCC. Given that there is no optimal therapy for metastatic pRCC, we sought to compare an existing standard (sunitinib) to putative MET kinase inhibitors. Methods: Eligible patients had pathologically verified pRCC, Zubrod performance status 0-1, and measurable metastatic disease. Patients may have received up to 1 prior systemic therapy excluding VEGF-directed agents. Patients were randomized 1:1:1:1 to receive either sunitinib 50 mg po qd (4 wks on/2 wks off), cabozantinib 60 mg po qd, crizotinib 250 mg po bid, or savolitinib 600 mg po qd. Patients were stratified by prior therapy and pRCC subtype (I vs II vs not otherwise specified [NOS]) based on local review. The primary objective was to compare progression-free survival (PFS) for each experimental arm versus sunitinib. With 41 eligible patients per arm, we estimated 85% power to detect a 75% improvement in median PFS with a 1-sided alpha of 0.10 using intent-to-treat analysis. A pre-planned futility analysis was performed after 50% of PFS events occurred. Secondary endpoints included toxicity, response rate, and overall survival. Results: Between 4/2016 and 12/2019, 152 patients were enrolled; 5 were ineligible. Median age was 66 (range:29-89) and 76% were male; 92% had no prior therapy. By local pathologic review, 18%, 54% and 28% of patients were characterized as having type I, type II and NOS histology, respectively. In contrast, the frequency of type I, type II, and NOS by central review was 30%, 45% and 25%, respectively. Accrual to the savolitinib and crizotinib arms was halted early for futility (PFS hazard ratio > 1.0 for both); accrual continued to completion in the sunitinib and cabozantinib arms. Median PFS was significantly higher with cabozantinib relative to sunitinib (Table). Grade 3 or 4 adverse events occurred in 69%, 72%, 37% and 39% of patients receiving sunitinib, cabozantinib, crizotinib and savolitinib, respectively; one grade 5 adverse event was seen with cabozantinib. Overall survival and response data will be presented. Conclusions: In this multi-arm randomized trial, only cabozantinib resulted in a statistically significant and clinically meaningful prolongation of PFS in pRCC patients compared to sunitinib. These data support cabozantinib as a reference standard for eligible patients with metastatic pRCC. Clinical trial information: NCT02761057 . [Table: see text]

Association between sites of metastases (mets) and outcomes with immune checkpoint inhibitor (ICI) therapy for advanced urothelial carcinoma (aUC)

445

Background: Different metastatic sites have variable prognostic implications in aUC. However, details on response and outcomes with ICI for particular mets is still unknown. We hypothesized that bone and liver mets would have poor response and outcomes with ICIs. Methods: We performed a retrospective cohort study in patients (pts) with aUC who received ICI. We compared overall response rate (ORR) and overall survival (OS) between pts with different mets at ICI initiation. We developed 4 different models: 1) lymph node (LN) only vs other; 2) visceral mets (bone, lung, liver) vs other; 3) bone + liver mets vs bone without liver vs liver without bone vs neither and 4) 6 factor model: a. LN +/- soft tissue/locoregional recurrence b. lung +/- (a) c. bone +/- (b) d. liver +/- (c) e. central nervous system (CNS) +/- (d) and f. other. ORR and OS were compared among groups using multivariable (adjusting for ECOG PS and hemoglobin<10g/dl) logistic regression and cox regression, respectively. Results: We identified 984 pts (24 institutions); 703 and 696 were included in OS and ORR analyses, respectively. Median age at ICI start was 71 (range 32-93), 77% white race, 74% men, 67% ever smokers, 72% pure UC, 18% upper tract UC, 55% extirpative surgery. Prevalence of LN, lung, bone and liver mets at ICI start was 74%, 32%, 27% and 21%, respectively. LN-only mets had significantly higher ORR (44% vs 22%, OR 2.6, p<0.05) and longer mOS (22 vs 8 months, HR 0.5, p<0.05) vs other mets. Visceral mets had significantly lower ORR (21% vs 35%, OR 0.5, p<0.05) and shorter mOS (7 vs 17 months, HR 1.8, p<0.05) vs non-visceral mets. Pts with bone and liver mets had significantly lower ORR and shorter OS vs those with bone or liver mets, which both had significantly lower ORR and shorter OS vs those with neither and with LN +/- local recurrence (Table). Conclusions: In the context of ICI treatment, bone, liver, lung or CNS mets were associated with lower ORR and/or shorter OS, and bone and liver mets were particularly associated with low ORR and short OS. LN-only mets were associated with higher ORR and longer OS. Further work is needed to interrogate site-specific tumor-host immune interactions and identify biomarkers. Research Sponsor: None[Table: see text]

Post-hoc analysis of long-term outcomes in patients with CR, PR, or SD to pembrolizumab (pembro) or platinum-based chemotherapy (chemo) as 1L therapy for advanced urothelial carcinoma (UC) in KEYNOTE-361

435

Background: The phase III KEYNOTE-361 study compared efficacy and safety of 1L pembro + chemo or pembro vs chemo in pts with advanced UC. The trial did not meet its primary endpoints of PFS or OS superiority for pembro + chemo vs chemo; formal testing for OS for pembro vs chemo was not performed. We present a post hoc landmark analysis to examine the durability of CR/PR/SD and long-term survival in pts with CR, PR, or SD to pembro vs chemo at week 9 in KEYNOTE-361 (NCT02853305). Methods: Landmark analyses of OS by CR/PR/SD at 9 weeks after randomization in the ITT population were performed. Pts were included if they had a best response of CR/PR/SD per RECIST v1.1 by blinded independent central review at the landmark date of week 9 (first imaging assessment per study protocol). Duration of CR/PR/SD and OS were estimated by the Kaplan-Meier method. No formal comparisons were performed. Results: 307 pts were randomized to receive pembro and 352 pts to receive chemo in the KEYNOTE-361 study. As of Apr 29, 2020, the median (range) time from randomization to data cutoff was 32.5 (22.0-42.4) mo for the pembo arm and 31.4 (22.1-41.6) mo for the chemo arm. In the landmark analysis, fewer pts had CR/PR/SD at week 9 with pembro (n=137 [45%]) than with chemo (n=253 [72%]). Median (range) duration of response for pembro vs chemo was 18.7 (4.4+-35.4+) vs 12.3 (0.0+-29.7+) mo for pts with CR, and 35.0 (1.1-36.1+) vs 6.1 (0.0+-36.3+) mo for pts with PR. Median (range) duration of SD was 4.8 mo (0.0-38.2+) with pembro and 4.6 mo (0.0-16.1+) with chemo. Median OS (95% CI) for pembro vs chemo was not reached (NR) (25.5-NR) vs NR (19.1-NR) for pts with CR; NR (NR-NR) vs 14.8 mo (12.1-21.0) for pts with PR; and 18.5 mo (13.8-28.8) vs 11.1 mo (8.1-14.6) for pts with SD, respectively. Long-term OS rates were higher with pembro vs chemo across all groups (CR/PR/SD) at week 9 (Table). Conclusions: In this post hoc landmark analysis, chemo was associated with more initial responses than pembro, whereas pembro was associated with longer median duration of CR and PR, and generally longer median OS than chemo. Among pts who achieved CR/PR/SD at week 9, the relative OS benefit for pembro vs chemo increased over time. Clinical trial information: NCT02853305. [Table: see text]

Impact of timing of adjuvant chemotherapy following radical cystectomy for bladder cancer on patient survival

BACKGROUND

Trials of adjuvant chemotherapy following radical cystectomy generally require chemotherapy to start within 90 days postoperatively. However, it is unclear, whether the interval between surgery and start of adjuvant therapy (S-AC-interval) impacts the oncological outcome.

METHODS

Using the Retrospective International Study of Invasive/Advanced Cancer of the Urothelium (RISC) data base, we identified patients who underwent radical cystectomy for muscle invasive bladder cancer and subsequent adjuvant chemotherapy. Univariate analysis of patient characteristics, surgical factors and tumor characteristics regarding their impact on S-AC-interval was performed using Kruskal-Wallis testing and Fisher's exact test. Analysis of progression-free (PFS) and overall survival (OS) (follow-up time beginning with the start date of adjuvant chemotherapy) was analyzed in relation to S-AC-interval (continuous and dichotomous with a cut-off at 90 days) using Kaplan-Meier method and COX regression analysis.

RESULTS

We identified 238 eligible patients (83.5% male, mean age: 63.4 years, 76.1% T3/T4, 66.4% pN+, 14.7% R+, 70.6% urothelial carcinoma, 71% cisplatin-based adjuvant chemotherapy). The majority of patients (n = 207, 87%) started chemotherapy within 90 days after surgery. Median S-AC-interval was 57 days (interquartile range 32.8). S-AC-interval did not have consistent association with any patient/tumor characteristics or surgery related factors (type of surgery, urinary diversion). Survival analysis using continuous S-AC-interval revealed a trend toward an impact of S-AC-interval on OS (hazard ratio 1.004, 95% confidence ratio 0.9997-1.0084, P = 0.071). With regards to PFS, that impact was shown to be statistically significant (hazard ratio 1.004, 95% confidence ratio 1.0003-1.0075, P = 0.032). In multivariate analysis, however, S-AC-interval was negated by tumor and patient related factors (pathological T-stage, N-stage, ECOG performance status). Accounting for eligibility criteria defined in some clinical trials, we extended our analysis dividing S-AC-interval in ≤90 and >90 days. Although we could confirm the trend toward better outcome in patients with a shorter S-AC interval in dichotomous analysis, neither differences in OS nor in PFS reached statistical significance (P = 0.438 and P = 0.056).

CONCLUSIONS

In a large multi-institutional experience, 87% of patients who received adjuvant chemotherapy received it within the guideline recommended window of 90 days. While it was not possible to determine whether this is the optimal cut-off, early start of adjuvant chemotherapy seems to be reasonable. Regarding prognosis, tumor-related pathological factors abrogated the importance of the S-AC-interval in our analysis.

Association of SPOP Mutations with Outcomes in Men with De Novo Metastatic Castration-sensitive Prostate Cancer

Recently, mutations in speckle-type pox virus and zinc finger protein (SPOP) gene (mutant SPOP [mtSPOP]) have been associated with improved outcomes to abiraterone in the castration-resistant setting. We hypothesized that mtSPOP would be associated with improved outcomes to systemic therapy in men with de novo metastatic castration-sensitive prostate cancer (d-mCSPC). Retrospective data of newly diagnosed d-mCSPC patients were collected from four institutions. Eligibility criteria included standard androgen deprivation therapy without intensification, and SPOP mutational status (mtSPOP or wild-type SPOP [wtSPOP]) determination by targeted next-generation sequencing from tumor biopsies. A total of 121 men (25 mtSPOP [21%] and 96 wtSPOP [79%]) were included. After adjusting for covariates, mtSPOP was significantly associated with better median progression-free survival (35 vs 13 mo; adjusted hazard ratio [HR] 0.47; p =  0.016) and overall survival (97 vs 69 mo; adjusted HR 0.32; p =  0.027), with similar HR and p value on the univariate analysis. These findings, upon external validation, may assist with counseling and prognostication in the clinic, and inform the design of future clinical trials in this setting. PATIENT SUMMARY: : Presence of tumor mutation in speckle-type pox virus and zinc finger protein (SPOP) gene was associated with improved survival outcomes in men with de novo metastatic castration-sensitive prostate cancer receiving standard androgen deprivation therapy.

The impact of BRAF mutation status on clinical outcomes with single-agent PD-1 inhibitor versus combination ipilimumab/nivolumab

10024

Background: Nearly half of all metastatic melanoma patients possess the BRAF V600 mutation. Several therapies are approved for BRAF mutant metastatic melanoma, but it is unclear if there is a differential outcome to various immunotherapy regimens. Our aim was to better assess if BRAF mutation status has any impact on survival to combination ipilimumab/nivolumab (I/N) versus single-agent PD-1 inhibitor (PD-1i). Methods: We performed a single center, retrospective analysis on a cohort of patients diagnosed with metastatic or unresectable melanoma from 2012 to 2019 at the University of Michigan who were treated with standard I/N or PD-1i (nivolumab or pembrolizumab). A univariate analysis of progression free survival (PFS) and overall survival (OS) was stratified by treatment type and BRAF mutation status. A multivariate Cox regression of survival was used to compare the effects of the treatment groups adjusted by BRAF status, age, gender, pre-treatment LDH level, prior treatment status, and brain metastases status. Results: 323 patients were identified. 132 had BRAF V600 mutation and 191 had BRAF wildtype (WT) status. 138 patients received I/N and 185 patients received PD-1i. In our univariate analysis, there was no difference in PFS [HR: 0.72, 95% CI, 0.46 – 1.13] or OS [HR: 0.78, 0.44 – 1.38] with I/N versus PD-1i in the BRAF mutant cohort, but there was improved PFS [HR: 0.55, 0.35 – 0.88) and OS [HR: 0.52, 0.28 – 0.95] with I/N compared to PD-1i in the BRAF WT group. In the multivariate analysis, the BRAF WT group continued to show PFS benefit with I/N compared to PD-1i [HR: 0.57, 95% CI, 0.35 – 0.95], but the OS benefit no longer achieved statistical significance [HR: 0.54, 0.28 – 1.03]. Conclusions: Our study results were discordant with the observation in the landmark CheckMate 067 trial, which noted improved PFS and OS with I/N compared to nivolumab alone in the BRAF mutant group and no difference in the BRAF WT group. In our real-world retrospective analysis, I/N over PD-1i should be considered as initial immunotherapy for metastatic melanoma patients regardless of BRAF mutation status, but even more favorably in BRAF WT.

Use of immune checkpoint inhibitors (ICIs) after prior ICI in metastatic renal cell carcinoma (mRCC): Results from a multicenter collaboration

5077

Background: Several ICIs are used in first and subsequent lines of therapy for mRCC, either alone or in combination with another ICI or targeted therapy (TT). There are no data on the efficacy and safety of using an ICI in patients who have already received an ICI in a prior line of therapy. Methods: We reviewed patients with mRCC at 8 institutions who received 2 separate lines of ICI therapy (ICI-1, ICI-2), including as a single-agent and/or combination with other agents. The primary outcomes were overall response rate (ORR) and time to progression (TTP) with ICI-1 and ICI-2. Immune-related adverse events (irAEs) were graded using CTCAEv5.0. Results: 65 patients were included. Median age at diagnosis of mRCC was 60 years (range 30-86) and the majority had clear cell RCC (n=56, 86%). Median follow-up was 3.5 years (95% CI 2.9-4.4). Median lines at which ICI-1 and ICI-2 were received were 1 (1-6) and 3 (2-8) respectively. Reasons for discontinuing ICI-1 were disease progression (n=47, 72%), toxicity (n=15, 23%) or other (n=3, 5%). Therapies received at ICI-2 were single-agent ICI (n=26, 40%), or combinations of ICI with another ICI (n=20, 31%), TT (n=11, 17%) or other agent (n=8, 12%). Responses to ICI-1 and ICI-2 are shown in the Table; ORR to ICI-2 was significantly lower than to ICI-1 (23% vs. 36%, p=0.044). Amongst those who responded to ICI-2 (n=14), 7 (50%) received single-agent ICI, and the remainder received ICI in combination with another ICI (n=4, 29%) or TT (n=3, 21%); 7 patients (50%) had previously responded to ICI-1. The ORR to ICI-2 was higher in responders to ICI-1 (32%) compared to those with SD (17%) or PD (15%) to ICI-1. Median TTP (mTTP) at ICI-2 was shorter compared to ICI-1 (5.3 months vs. 8.5 months, Wilcoxon p=0.024). 29 patients (45%) experienced an irAE with ICI-2; 8 (12%) and 3 (5%) had a grade 3 or 4 irAE respectively, with 3 (30%) of these patients having previously had ≥grade 3 irAE to ICI-1. There were no treatment-related deaths. Conclusions: The ORR to ICI-2 was 23%, which is comparable to that seen with ICI after prior TT. Responses were seen even amongst those receiving single-agent ICI at ICI-2 and the likelihood of response to ICI-2 was higher if a patient had previously responded to ICI-1. No increase in toxicity with ICI-2 was apparent. Additional data from prospective studies are needed to determine whether sequential ICI has a role in treatment of mRCC. [Table: see text]