Repeat Next-Generation Sequencing Testing on Progression in Men With Metastatic Prostate Cancer Can Identify New Actionable Alterations

PURPOSE

There are limited data available on the real-world patterns of molecular testing in men with advanced prostate cancer. We thus sought to evaluate next-generation sequencing (NGS) testing in the United States, focused on single versus serial NGS testing, the different disease states of testing (hormone-sensitive v castration-resistant, metastatic vs nonmetastatic), tissue versus plasma circulating tumor DNA (ctDNA) assays, and how often actionable data were found on each NGS test.

METHODS

The Prostate Cancer Precision Medicine Multi-Institutional Collaborative Effort clinical-genomic database was used for this retrospective analysis, including 1,597 patients across 15 institutions. Actionable NGS data were defined as including somatic alterations in homologous recombination repair genes, mismatch repair deficiency, microsatellite instability (MSI-high), or a high tumor mutational burden ≥10 mut/MB.

RESULTS

Serial NGS testing (two or more NGS tests with specimens collected more than 60 days apart) was performed in 9% (n = 144) of patients with a median of 182 days in between test results. For the second NGS test and beyond, 82.1% (225 of 274) of tests were from ctDNA assays and 76.1% (217 of 285) were collected in the metastatic castration-resistant setting. New actionable data were found on 11.1% (16 of 144) of second NGS tests, with 3.5% (5 of 144) of tests detecting a new BRCA2 alteration or MSI-high. A targeted therapy (poly (ADP-ribose) polymerase inhibitor or immunotherapy) was given after an actionable result on the second NGS test in 31.3% (5 of 16) of patients.

CONCLUSION

Repeat somatic NGS testing in men with prostate cancer is infrequently performed in practice and can identify new actionable alterations not present with initial testing, suggesting the utility of repeat molecular profiling with tissue or blood of men with metastatic castration-resistant prostate cancer to guide therapy choices.

Clinical implications of AR alterations in advanced prostate cancer: a multi-institutional collaboration

BACKGROUND

AR gene alterations can develop in response to pressure of testosterone suppression and androgen receptor targeting agents (ARTA). Despite this, the relevance of these gene alterations in the context of ARTA treatment and clinical outcomes remains unclear.

METHODS

Patients with castration-resistant prostate cancer (CRPC) who had undergone genomic testing and received ARTA treatment were identified in the Prostate Cancer Precision Medicine Multi-Institutional Collaborative Effort (PROMISE) database. Patients were stratified according to the timing of genomic testing relative to the first ARTA treatment (pre-/post-ARTA). Clinical outcomes such as time to progression, PSA response, and overall survival were compared based on alteration types.

RESULTS

In total, 540 CRPC patients who received ARTA and had tissue-based (n = 321) and/or blood-based (n = 244) genomic sequencing were identified. Median age was 62 years (range 39-90) at the time of the diagnosis. Majority were White (72.2%) and had metastatic disease (92.6%) at the time of the first ARTA treatment. Pre-ARTA genomic testing was available in 24.8% of the patients, and AR mutations and amplifications were observed in 8.2% and 13.1% of the patients, respectively. Further, time to progression was longer in patients with AR amplifications (25.7 months) compared to those without an AR alteration (9.6 months; p = 0.03). In the post-ARTA group (n = 406), AR mutations and AR amplifications were observed in 18.5% and 35.7% of the patients, respectively. The most common mutation in post-ARTA group was L702H (9.9%).

CONCLUSION

In this real-world clinicogenomics database-driven study we explored the development of AR alterations and their association with ARTA treatment outcomes. Our study showed that AR amplifications are associated with longer time to progression on first ARTA treatment. Further prospective studies are needed to optimize therapeutic strategies for patients with AR alterations.

Outcomes of Consolidative Nephrectomy following Primary Immunotherapy in Advanced Renal Cell Carcinoma: A Multicenter Analysis

BACKGROUND

To evaluate effect and outcomes of combination primary immunotherapy (IO) and nephrectomy for advanced renal cell carcinoma (RCC).

METHODS

We conducted a multicenter, retrospective analysis of patients with advanced/metastatic RCC who received IO followed by nephrectomy. Primary outcome was Bifecta (negative surgical margins and no 30-day surgical complications). Secondary outcomes included progression-free survival (PFS) following surgery, reduction in tumor/thrombus size, RENAL score, and clinical/pathologic downstaging. Cox regression multivariable analysis was conducted for predictors of Bifecta and PFS. Kaplan-Meier analysis assessed PFS, comparing Bifecta and non-Bifecta groups.

RESULTS

A total of 56 patients were analyzed (median age 63 years; median follow-up 22.5 months). A total of 40 (71.4%) patients were intermediate IMDC risk. Patients were treated with immunotherapy for median duration of 8.1 months. Immunotherapy resulted in reductions in tumor size (P < .001), thrombus size (P = .02), and RENAL score (P < .001); 38 (67.9%) patients were clinically downstaged on imaging (P < .001) and 25 (44.6%) patients were pathologically downstaged following surgery (P < .001). Bifecta was achieved in 38 (67.9%) patients. Predictors for bifecta achievement included decreasing tumor size (HR 1.08, P = .043) and pathological downstaging (HR 2.13, P = .047). Bifecta (HR 5.65, P = .009), pathologic downstaging (HR 5.15, P = .02), and increasing reduction in tumor size (HR 1.2, P = .007) were associated with improved PFS. Bifecta patients demonstrated improved 2-year PFS (84% vs. 71%, P = .019).

CONCLUSIONS

Primary immunotherapy reduced tumor/thrombus size and complexity. Pathologically downstaged patients were more likely to achieve bifecta, and these patients displayed improved 2-year PFS. Our study supports further inquiry in the use of CRN following primary immunotherapy for advanced renal cancer.

5-hydroxymethylcytosine sequencing in plasma cell-free DNA identifies unique epigenomic features in prostate cancer patients resistant to androgen deprivation therapy

Background

Currently there are no biomarkers to identify resistance to androgen-deprivation therapy (ADT) in men with hormone-naive prostate cancer. 5-hydroxymethylcytosines (5hmC) in the gene body are associated with gene activation and are critical for epigenomic regulation of cancer progression.

Objective

To evaluate whether 5hmC signature in cell-free DNA (cfDNA) predicts early ADT resistance.

Design Setting and Participants

Serial plasma samples from 55 prostate cancer patients receiving ADT were collected at three timepoints including baseline (prior to initiating ADT, N=55), 3-month (after initiating ADT, N=55), and disease progression (N=15) within 24 months or 24-month if no progression was detected (N=14). 20 of the 55 patients showed disease progression during the 24-month follow-up. The remaining 35 patients showed no progression in the same follow-up period.

Outcome Measurements and Statistical Analysis

cfDNA (5-10ng) was used for selective chemical labeling (hMe-Seal) sequencing to map 5hmC abundance across the genome. Read counts in gene bodies were normalized with DESeq2. Differential methylation and gene set enrichment analyses were performed to identify the 5hmC-enriched genes and biological processes that were associated with disease progression. Kaplan-Meir analysis was utilized to determine the association of 5hmC signatures with progression-free survival.

Results and Limitations

5hmC-sequencing generated an average of 18.6 (range 6.03 to 42.43) million reads per sample with 98% (95-99%) mappable rate. Baseline sample comparisons identified significant 5hmC difference in 1,642 of 23,433 genes between 20 patients with progression and 35 patients without progression (false discovery rate, FDR<0.1). Patients with progression showed significant enrichments in multiple hallmark gene sets with androgen responses as the top enriched gene set (FDR=1.19E-13). Interestingly, this enrichment was driven by a subgroup of patients with disease progression featuring a significant 5hmC hypermethylation of the gene sets involving AR, FOXA1 and GRHL2. To quantify overall activities of these gene sets, we developed a gene set activity score algorithm using a mean value of log2 ratios of gene read counts in an entire gene set. We found that the activity scores in these gene sets were significantly higher in this subgroup of patients with progression than in the remaining patients regardless of the progression status. Furthermore, the high activity scores in these gene sets were associated with poor progression-free survival (p <0.05). Longitudinal analysis showed that activity scores in this subgroup with progression were significantly reduced after 3-month ADT but returned to high levels when the disease was progressed.

Conclusions

5hmC-sequencing in cfDNA identified a subgroup of prostate cancer patients with preexisting activation (5hmC hypermethylation) of gene sets involving AR, FOXA1 and GRHL2 before initiating ADT. Activity scores in these gene sets may serve as sensitive biomarkers to determine treatment resistance, monitor disease progression and potentially identify patients who would benefit from upfront treatment intensification. More studies are needed to validate this initial finding.

Patient summary

There are no clinical tests to identify prostate cancer patients who will develop early resistance to androgen deprivation therapy within 24 months. In this study, we evaluated cell-free DNA epigenomic modification in blood and identified significant enrichment of 5-hydroxymethylation in androgen response genes in a subgroup of patients with treatment resistance. High level 5-hydroxylmethylation in these genes may serve as a discriminative biomarker to diagnose patients who are likely to experience early failure during androgen deprivation therapy.

Biomarker-Directed Therapy in Black and White Men With Metastatic Castration-Resistant Prostate Cancer

Importance

Black men have higher incidence and mortality from prostate cancer. Whether precision oncology disparities affect Black men with metastatic castration-resistant prostate cancer (mCRPC) is unknown.

Objective

To compare precision medicine data and outcomes between Black and White men with mCRPC.

Design, Setting, and Participants

This retrospective cohort study used data collected by the Prostate Cancer Precision Medicine Multi-Institutional Collaborative Effort (PROMISE) consortium, a multi-institutional registry with linked clinicogenomic data, from April 2020 to December 2021. Participants included Black and White patients with mCRPC with molecular data. Data were analyzed from December 2021 to May 2023.

Exposures

Database-reported race and ethnicity.

Main Outcomes and Measures

The primary outcome was the frequency of actionable molecular data, defined as the presence of mismatch repair deficiency (MMRD) or high microsatellite instability (MSI-H), homologous recombination repair deficiency, or tumor mutational burden of 10 mutations per megabase or greater. Secondary outcomes included the frequency of other alterations, the type and timing of genomic testing performed, and use of targeted therapy. Efficacy outcomes were prostate-specific antigen response rate, site-reported radiographic response, and overall survival.

Results

A total of 962 eligible patients with mCRPC were identified, including 204 Black patients (21.2%; median [IQR] age at diagnosis, 61 [55-67] years; 131 patients [64.2%] with Gleason scores 8-10; 92 patients [45.1%] with de novo metastatic disease) and 758 White patients (78.8%; median [IQR] age, 63 [57-69] years; 445 patients [58.7%] with Gleason scores 8-10; 310 patients [40.9%] with de novo metastatic disease). Median (IQR) follow-up from mCRPC was 26.6 (14.2-44.7) months. Blood-based molecular testing was more common in Black men (111 men [48.7%]) than White men (317 men [36.4%]; P < .001). Rates of actionable alterations were similar between groups (65 Black men [32.8%]; 215 White men [29.1%]; P = .35), but MMRD or MSI-H was more common in Black men (18 men [9.1]) than White men (36 men [4.9%]; P = .04). PTEN alterations were less frequent in Black men than White men (31 men [15.7%] vs 194 men [26.3%]; P = .003), as were TMPRSS alterations (14 men [7.1%] vs 155 men [21.0%]; P < .001). No other differences were seen in the 15 most frequently altered genes, including TP53, AR, CDK12, RB1, and PIK3CA. Matched targeted therapy was given less frequently in Black men than White men (22 men [33.5%] vs 115 men [53.5%]; P = .008). There were no differences in response to targeted therapy or survival between the two cohorts.

Conclusions and Relevance

This cohort study of men with mCRPC found higher frequency of MMRD or MSI-H and lower frequency of PTEN and TMPRSS alterations in Black men compared with White men. Although Black men received targeted therapy less frequently than White men, no differences were observed in clinical outcomes.

Clinical implications of AR alterations in advanced prostate cancer: A multi-institutional collaboration

Background

AR gene alterations can develop in response to pressure of testosterone suppression and androgen receptor targeting agents (ARTA). Despite this, the relevance of these gene alterations in the context of ARTA treatment and clinical outcomes remains unclear.

Methods

Patients with castration-resistant prostate cancer (CRPC) who had undergone genomic testing and received ARTA treatment were identified in the Prostate Cancer Precision Medicine Multi-Institutional Collaborative Effort (PROMISE) database. Patients were stratified according to the timing of genomic testing relative to the first ARTA treatment (pre-/post-ARTA). Clinical outcomes such as time to progression, PSA response, and overall survival were compared based on alteration types.

Results

In total, 540 CRPC patients who received ARTA and had tissue-based (n=321) and/or blood-based (n=244) genomic sequencing were identified. Median age was 62 years (range 39-90) at the time of the diagnosis. Majority were White (72.2%) and had metastatic disease (92.6%) at the time of the first ARTA treatment. Pre-ARTA genomic testing was available in 24.8% of the patients, and AR mutations and amplifications were observed in 8.2% and 13.1% of the patients, respectively. Further, time to progression was longer in patients with AR amplifications (25.7 months) compared to those without an AR alteration (9.6 months; p=0.03). In the post-ARTA group (n=406), AR mutations and AR amplifications were observed in 18.5% and 35.7% of the patients, respectively. The most common mutation in post-ARTA group was L702H (9.9%).

Conclusion

To our knowledge, this is the largest real-world clinicogenomics database-driven study exploring the development of ARalterations and their association with ARTA treatment outcomes. Our study showed that AR amplifications are associated with longer time to progression on first ARTA treatment. Further prospective studies are needed to optimize therapeutic strategies for patients with AR alterations.

Pathological Outcomes of Patients With Advanced Renal Cell Carcinoma Who Receive Nephrectomy Following Immunotherapy

BACKGROUND

Even though cytoreductive nephrectomy (CN) was once the standard of care for patients with advanced renal cell carcinoma (RCC), its role in treatment has not been well analyzed or defined in the era of immunotherapy (IO).

MATERIALS AND METHODS

This study analyzed pathological outcomes in patients with advanced or metastatic RCC who received IO prior to CN. This was a multi-institutional, retrospective study of patients with advanced or metastatic RCC. Patients were required to receive IO monotherapy or combination therapy prior to radical or partial CN. The primary endpoint assessed surgical pathologic outcomes, including American Joint Committee on Cancer (AJCC) staging and frequency of downstaging, at the time of surgery. Pathologic outcomes were correlated to clinical variables using a Wald-chi squared test from Cox regression in a multi-variable analysis. Secondary outcomes included objective response rate (ORR) defined by response evaluation criteria in solid tumors (RECIST) version 1.1 and progression-free survival (PFS), which were estimated using the Kaplan-Meier method with reported 95% CIs.

RESULTS

Fifty-two patients from 9 sites were included. Most patients were male (65%), 81% had clear cell histology, 11% had sarcomatoid differentiation. Overall, 44% of patients experienced pathologic downstaging, and 13% had a complete pathologic response. The ORR immediately prior to nephrectomy was stable disease in 29% of patients, partial response in 63%, progressive disease in 4%, and 4% unknown. Median follow-up for the entire cohort was 25.3 months and median PFS was 3.5 years (95% CI, 2.1-4.9).

CONCLUSIONS

IO-based interventions prior to CN in patients with advanced or metastatic RCC demonstrates efficacy, with a small fraction of patients showing a complete response. Additional prospective studies are warranted to investigate the role of CN in the modern IO-era.

The Confusion Surrounding Androgen Deprivation Therapy and Cognitive Dysfunction

There are varied associations that have been identified between the use of androgen deprivation therapy (ADT) and the development of cognitive decline. We highlight the first studies to evaluate chronic use of ADT, other systemic treatments for prostate cancer, and genetic polymorphisms in this context.

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

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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.

Immunohistochemical (IHC) subtypes of metastatic bladder cancer (mBC) using GATA3 and CK5/6

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Background: Genomic analyses have identified that bladder cancers can be divided into distinct molecular subtypes: luminal and basal. IHC markers GATA3 and CK5/6 have demonstrated >80% accuracy in assessing the luminal and basal subtypes of primary bladder tumors and may be easily utilized in clinical practice. Correlation of the primary bladder subtype with that of metastatic sites has not been demonstrated and associations with clinical outcomes are uncertain. Methods: We retrospectively identified patients with mBC who were treated with systemic therapy and had biopsies of either primary bladder or metastatic sites. Patient demographic, metastatic sites, treatment patterns, and clinical outcomes were recorded. Tissue microarrays (TMA) were constructed from primary and/or metastatic tumors. IHC was performed using mouse monoclonal antibodies: GATA-3 (L50-823, Pharmingen, 1:200) and cytokeratin 5/6 (XM26, Thermo Fisher, 1:100). Luminal (GATA3+, CK5/6-), basal (GATA3-, CK5/6+), double positive (GATA3+, CK5/6+) or double negative (GATA3-, CK5/6-) subtyping was applied. Concordance of matched bladder and metastatic pairs was quantified using Cohen’s kappa. Wilcoxon rank-sum tests were used for comparison of continuous and ordinal measures and chi-square tests were performed for comparison of categorical measures. Survival was estimated by Kaplan-Meier method; multivariable Cox analysis was performed. Results: Of 62 specimens, 37 bladder and 16 metastatic sites were interpretable. Four IHC subtype patterns were identified, most were luminal (n=20) followed by double-positive (n=12), basal (n=5), and double-negative (n=5). Of 10 pairs of matched primary tumor and metastatic sites, there was near-perfect subtype concordance between primary and metastatic tumors (κ=0.84; 95% CI:0.58-1.00). No association between sites of metastatic progression and subtype were identified, nor was there any difference in overall survival between the subtypes (p = 0.70). The basal subtype had numerically worse survival compared to the luminal subtype, HR =0.164 (95% CI: 0.02-1.58, p=0.12). Conclusions: IHC subtyping by GATA3 and CK5/6 is feasible in the clinical setting and showed strong correlation between primary and metastatic sites. A larger analysis is planned to further investigate associations with clinical features and outcomes. [Table: see text]

Impact of pre-existing anemia and/or packed red blood cell transfusion prior to Radium-223 administration on oncologic outcomes

67

Background: Radium-223 (Ra-223), a targeted alpha-emitting radiopharmaceutical approved for the treatment of metastatic prostate cancer (mPC), can cause myelosuppression. In the ALSYMPCA trial 30% of patients developed cytopenias, including 13% with grade 3/4 anemia. Therefore, it is recommended that only men with a hemoglobin ≥10 g/dL, platelet count ≥100,000/mm3, and ANC ≥1,500/mm3 be considered for Ra-223. Since the FDA approval of Ra-223 in 2013, several new treatments have been approved for men with mPC. With the changing therapeutic landscape, we anticipate more patients (pts) will have preexisting cytopenia prior to Ra-223 consideration. Hence, clinicians are increasingly likely to face the dilemma of whether it is safe and efficacious to administer Ra-223 in the setting of Hgb ≤10 with/without RBC transfusion support. Methods: We retrospectively identified pts with mPC treated with Ra-223, including a subset of men with Hgb <10g/dl at the Medical College of Wisconsin and Tulane Cancer Center from 2014 – 2019. Clinical data including demographics, prior cancer treatments, laboratory data, blood product transfusion data, and oncologic outcomes were collected. Survival was estimated using Kaplan-Meier method and statistical analysis was conducted using student’s t-test. Results: Sixty-two pts were identified. Median age at the time of Ra-223 was 75.3 years. Of these, nearly 20% (n=12) had a Hgb <10 g/dL and/or received RBC transfusions to meet “eligibility criteria” prior to beginning Ra-223 treatments. Compared to men who had Hgb >10g/dL, men with Hgb <10g/dL required more RBC transfusions both during and after Ra-223 treatment and had significantly worse oncologic outcomes. No patients experienced treatment delays of more than 1 week. There were no significant differences in the median number of treatments prior to Ra-223, median number of Ra-223 treatments received, platelet count nadir, or ANC nadir. Conclusions: Pre-existing Hgb < 10 g/dl and/or RBC transfusions prior to Ra-223 therapy is associated with worse oncologic outcomes in mPC, suggesting that the benefit of Ra-223 is limited in this subset. A larger sample size is needed to further validate our findings. Multivariable analysis is planned. [Table: see text]

Impact of cytoreductive nephrectomy (CRN) on overall survival (OS) in metastatic non–clear cell renal cancer (nccRCC)

730

Background: Non-clear cell renal cell carcinoma (nccRCC) accounts for 25% of kidney cancer diagnoses and encompasses a diverse group of kidney tumors with distinct biology for which treatment in the metastatic setting is evolving. The role of CRN for nccRCC population in the current treatment landscape remains unclear. Methods: We retrospectively identified patients (pts) with nccRCC from The National Cancer Database (NCDB) participant user file (PUF) for Kidney and Renal Pelvis Tumors. Pts with de novo metastatic disease diagnosed between 2006 and 2017, received systemic treatment (trt) with immunotherapy (IO) or non-immunotherapy (NIO) and either underwent or could have undergone a CRN were selected. Demographic and disease characteristics were summarized using descriptive statistics. The cumulative incidence of CRN with death without CRN as a competing risk, was estimated using the Nelson-Aalen estimator. The association of each demographic and disease characteristic on the cumulative incidence of CRN was evaluated using univariate Fine-Gray regression. The effect of CRN on survival was visualized using a Simon-Makuch plot. P values were based on Mantel-Byar test. Cox regression with a time-dependent predictor was used to estimate the change in the hazard of death after CRN. Results: We identified 3644 pts, 72% male, mean age 61 ±13 years. Nearly 40% of pts (n=1453) had sarcomatoid histology, followed by 30% with papillary (n=1075). Most pts, 96% (n=3489) received NIO systemic trt and only 9% were treated with IO (n=319). Nearly half of the study population (45%) underwent CRN (n=1642). Of these, 95% received NIO trt (n=1564) and 9% received IO (n=152). Pts who underwent CRN were younger and less likely to have bone, brain or liver metastases. Minority pts were less likely to undergo CRN. Mean time from dx to surgery was 1.1 ±1.7 months. For all pts, mOS was 9 months (95% CI: 8.6-9.4). OS was improved for pts who underwent CRN vs those who did not (11.3 vs 7.5 months, p<0.0001). In multivariate analysis, cytoreductive nephrectomy was associated with a reduction in the risk of death, HR 0.73 (95% CI: 0.68, 0.80, p<.0001). Conclusions: For pts with de novo metastatic nccRCC, CRN is associated with improved outcomes. Further analysis regarding the effect of treatment regimens on survival outcomes is warranted and planned. Prospective randomized trials in the modern treatment era are needed to further assess the timing and impact of CRN on outcomes in pts with metastatic nccRCC. [Table: see text]

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]

Comprehensive genomic profiling: Does timing matter?

Purpose

There is variability in utilization of Comprehensive Genomic Profiling (CGP) in most of the metastatic solid tumors (MST). We evaluated the CGP utilization patterns and its impact on outcomes at an academic tertiary center.

Patients and Methods

Institutional database was reviewed for CGP data in adult patients with MST between 01/2012 - 04/2020. Patients were categorized based on interval between CGP and metastatic diagnosis; 3 tertiles of distribution (T1-earliest to the diagnosis, T3-furthest), and pre-mets (CGP performed prior to diagnosis of metastasis). Overall survival (OS) was estimated from the time of metastatic diagnosis with left truncation at the time of CGP. Cox regression model was used to estimate the impact of timing of CGP on survival.

Results

Among 1,358 patients, 710 were female, 1,109 Caucasian, 186 Afro-Americans, and 36 Hispanic. The common histologies were lung cancer (254; 19%), colorectal cancer (203; 15%), gynecologic cancers (121; 8.9%), and pancreatic cancer (106; 7.8%). Time interval between diagnosis of metastatic disease and CGP was not statistically significantly different based on sex, race and ethnicity after adjusting for histologic diagnoses with 2 exceptions - Hispanics with lung cancer had delayed CGP compared to non-Hispanics (p =0.019) and females with pancreas cancer had delayed CGP compared to males (p =0.025). Lung cancer, gastro-esophageal cancer and gynecologic malignancies had better survival if they had CGP performed during the first tertile after metastatic diagnosis.

Conclusion

CGP utilization across cancer types was equitable irrespective of sex, race and ethnicity. Early CGP after metastatic diagnosis might have effect on treatment delivery and clinical outcomes in cancer type with more actionable targets.

Concurrent durvalumab and radiation therapy (DUART) followed by adjuvant durvalumab in patients with localized urothelial cancer of bladder: results from phase II study, BTCRC-GU15-023

BACKGROUND

Patients with bladder cancer (BC) who are cisplatin ineligible or have unresectable disease have limited treatment options. Previously, we showed targeting programmed death-ligand 1 (PD-L1) with durvalumab (durva) and radiation therapy (RT) combination was safe in BC. We now report results from a phase II study evaluating the toxicity and efficacy of durva and RT in localized BC.

METHODS

This is a single-arm, multi-institutional phase II study; N=26. Enrolled patients had pure or mixed urothelial BC (T2-4 N0-2 M0) with unresectable tumors and were unfit for surgery or cisplatin ineligible. Patients received durva concurrently with RT ×7 weeks, followed by adjuvant durva × 1 year.

PRIMARY ENDPOINTS

(A) progression-free survival (PFS) at 1 year and (B) disease control rate (DCR) post adjuvant durva. Key secondary endpoints: (A) complete response (CR) post durvaRT (8 weeks), (B) overall survival (OS), (C) PFS and (D) toxicity. Correlative studies included evaluation of baseline tumor and blood (baseline, post durvaRT) for biomarkers.

RESULTS

Median follow-up was 27 months. Evaluable patients: 24/26 post durvaRT, 22/26 for DCR post adjuvant durva, all patients for PFS and OS. Post adjuvant durva, DCR was seen in 72.7%, CR of 54.5%. 1-year PFS was 71.5%, median PFS was 21.8 months. 1-year OS was 83.8%, median OS was 30.8 months. CR at 8 weeks post durvaRT was 62.5%. Node positive (N+) patients had similar median PFS and OS. DurvaRT was well tolerated. Grade ≥3 treatment-related adverse events: anemia, high lipase/amylase, immune-nephritis, transaminitis, dyspnea (grade 4-COPD/immune), fatigue, rash, diarrhea and scleritis. No difference in outcome was observed with PD-L1 status of baseline tumor. Patients with CR/PR or SD had an increase in naïve CD4 T cells, a decrease in PD-1+CD4 T cells at baseline and an increase in cytokine-producing CD8 T cells, including interferon gamma (IFNγ) producing cells, in the peripheral blood.

CONCLUSION

Durva with RT followed by adjuvant durva was safe with promising efficacy in localized BC patients with comorbidities, including N+ patients. Larger randomized studies, like S1806 and EA8185, are needed to evaluate the efficacy of combining immunotherapy and RT in BC.

TRIAL REGISTRATION NUMBER

NCT02891161.

Bystander LECT2 amyloidosis in tumor nephrectomy

Pathologic evaluation of the non-neoplastic renal parenchyma in tumor nephrectomy specimens is critical and can detect both renal-limited and systemic pathologies. We report the case of a 69-year-old Punjabi male who underwent cytoreductive nephrectomy for advanced renal cell carcinoma after immunotherapy. We detected clinically unexpected leukocyte chemotactic factor 2 (LECT2) amyloidosis during pathologic analysis of the surrounding non-neoplastic renal parenchyma, which was confirmed by mass spectrometry. LECT2 amyloidosis occurs predominantly in Hispanic patients and has only rarely been described in Punjabi patients. This case highlights the importance of careful pathologic evaluation of the non-neoplastic renal parenchyma of nephrectomy specimens and raises awareness that LECT2 amyloidosis can occur outside of the typical demographic of Hispanic patients.

Cabozantinib Safety With Different Anticoagulants in Patients With Renal Cell Carcinoma

BACKGROUND

In patients with renal cell carcinoma (RCC) on cabozantinib, venous thromboembolism (VTE) management remains challenging due to limited safety data regarding direct oral anticoagulants (DOACs) use in conjunction with cabozantinib. We investigated the safety of cabozantinib with different anticoagulants in patients with RCC.

METHODS

In this retrospective multicenter study (9 sites), patients with advanced RCC were allocated into 4 groups: (1) cabozantinib without anticoagulation, cabozantinib with concomitant use of (2) DOACs, (3) low molecular weight heparin (LMWH), or (4) warfarin. The primary safety endpoint was the proportion of major bleeding events (defined per International Society on Thrombosis and Hemostasis criteria). The primary efficacy endpoint was the proportion of new/recurrent VTE while anticoagulated.

RESULTS

Between 2016 and 2020, 298 patients with RCC received cabozantinib (no anticoagulant = 178, LMWH = 41, DOAC = 64, and warfarin = 15). Most patients had clear cell histology (78.5%) and IMDC intermediate/poor disease (78.2%). Cabozantinib was first, second, or ≥ third line in 21.8%, 31.9%, 43.3% of patients, respectively. Overall, there was no difference in major bleeding events between the no anticoagulant, LMWH, and DOAC groups (P = .088). Rate of new/recurrent VTE was similar among anticoagulant groups. Patients with a VTE had a statistically significantly worse survival than without a VTE (HR 1.48 [CI 95% 1.05-2.08, P = .02]).

CONCLUSION

This real-world cohort provides first data on bleeding and thrombosis complications in patients with RCC treated with cabozantinib with or without concurrent anticoagulation. DOACs appear safe for VTE treatment for patients with RCC on cabozantinib, but optimized anticoagulation management, including individualized risk-benefit discussion, remains important in clinical practice.

Talazoparib, a Poly(ADP-ribose) Polymerase Inhibitor, for Metastatic Castration-resistant Prostate Cancer and DNA Damage Response Alterations: TALAPRO-1 Safety Analyses

BACKGROUND

The phase II TALAPRO-1 study (NCT03148795) demonstrated durable antitumor activity in men with heavily pretreated metastatic castration-resistant prostate cancer (mCRPC). Here, we detail the safety profile of talazoparib.

PATIENTS AND METHODS

Men received talazoparib 1 mg/day (moderate renal impairment 0.75 mg/day) orally until radiographic progression, unacceptable toxicity, investigator decision, consent withdrawal, or death. Adverse events (AEs) were evaluated: incidence, severity, timing, duration, potential overlap of selected AEs, dose modifications/discontinuations due to AEs, and new clinically significant changes in laboratory values and vital signs.

RESULTS

In the safety population (N = 127; median age 69.0 years), 95.3% (121/127) experienced all-cause treatment-emergent adverse events (TEAEs). Most common were anemia (48.8% [62/127]), nausea (33.1% [42/127]), decreased appetite (28.3% [36/127]), and asthenia (23.6% [30/127]). Nonhematologic TEAEs were generally grades 1 and 2. No grade 5 TEAEs or deaths were treatment-related. Hematologic TEAEs typically occurred during the first 4-5 months of treatment. The median duration of grade 3-4 anemia, neutropenia, and thrombocytopenia was limited to 7-12 days. No grade 4 events of anemia or neutropenia occurred. Neither BRCA status nor alteration origin significantly impacted the safety profile. The median (range) treatment duration was 6.1 (0.4-24.9) months; treatment duration did not impact the incidence of anemia. Only 3 of the 15 (11.8% [15/127]) permanent treatment discontinuations were due to hematologic TEAEs (thrombocytopenia 1.6% [2/127]; leukopenia 0.8% [1/127]).

CONCLUSION

Common TEAEs associated with talazoparib could be managed through dose modifications/supportive care. Demonstrated efficacy and a manageable safety profile support continued evaluation of talazoparib in mCRPC.

CLINICALTRIALS.GOV IDENTIFIER

NCT03148795.

A phase 2 study of cabozantinib in combination with atezolizumab as neoadjuvant treatment for muscle-invasive bladder cancer (HCRN GU18-343) ABATE study

TPS4618

Background: ABACUS and PURE-01 trials demonstrated the activity of single agent atezolizumab and pembrolizumab respectively as neoadjuvant therapy for muscle invasive bladder carcinoma (MIBC). However, downstaging to non-muscle invasive disease was noted in only 50 percent of patients. Resistance to programmed death (PD)- 1/L1 antibodies is likely to include factors such as impaired dendritic cell maturation/function, infiltration of T-Regs and myeloid derived suppressor cells, impaired T-cell priming and T-cell trafficking in tumors. Cabozantinib is a tyrosine kinase inhibitor which targets MET, AXL, MER, Tyro3 and VEGFR2. Cabozantinib has a unique immunomodulatory profile and has demonstrated clinical activity as monotherapy and in combination with PD-1/L1 antibodies in various solid tumors including urothelial cancer (UC), renal cell, castrate- resistant prostate and non-small cell lung cancer. We hypothesize that the combination of cabozantinib and atezolizumab as neoadjuvant therapy for MIBC would improve rates of pathologic downstaging compared to single-agent checkpoint inhibitors. Methods: ABATE is an open-label, single arm, multi-center study to assess the efficacy and safety of cabozantinib with atezolizumab as neoadjuvant therapy for cT2-T4aN0/xM0 MIBC. An estimated 42 patients will be enrolled to obtain 38 evaluable patients, and the study will have over 80% power to declare the investigational combination to be successful using a Bayesian evaluation at 90% posterior probability cutoff, if the response probability is 59%, i.e., 20% higher than the 39% response rate with the single agent atezolizumab. Eligible patients will receive cabozantinib 40 mg PO daily with atezolizumab 1200mg every 3 weeks for a total duration of 9 weeks (3 cycles) followed by radical cystectomy. Adults (≥18 years) with resectable MIBC who are either cisplatin-ineligible or decline cisplatin-based chemotherapy are eligible. Patients are required to have an ECOG PS of 0-2 and provide tumor tissue for PD-L1 expression analysis. UC should be predominant component (≥ 50%). Previous systemic anticancer therapies for MIBC are not permitted. CT/MRI will be performed before investigational therapy and cystectomy. Primary endpoint is pathologic response rate defined as the absence of residual muscle-invasive cancer in the surgical specimen (< pT2). Secondary endpoints are safety and toxicity, pathologic complete response rate and event-free survival. Exploratory end points include patient-reported outcomes and outcome associations with biomarkers. Accrual began May 2020. Clinical trial information: NCT04289779.

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]

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]

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]

Pathologic outcomes at cytoreductive nephrectomy (CN) following immunotherapy (IO) for patients with advanced renal cell carcinoma (RCC)

334

Background: IO, either as combination therapy in the frontline or monotherapy in the second line, has improved outcomes for patients with advanced RCC. With the movement away from upfront CN, limited data are available on the outcomes of patients who receive IO with delayed CN. In this study, we characterized the pathologic and survival outcomes for patients who received IO followed by CN. Methods: We conducted a multi-center, retrospective analysis of patients with advanced/metastatic RCC having received IO combination or monotherapy followed by CN. An IRB-approved and HIPAA-compliant registry was used to collect data from the electronic medical record. Our primary endpoint was the degree of pathologic downstaging comparing baseline clinical T stage to pathologic T stage following IO. Secondary endpoints included investigator assessed response using RECIST principals, progression-free survival (PFS), and overall survival (OS). Results: We identified53 patients with advanced RCC across 9 institutions who were eligible for the study. The median age was 63 years, 72% were white, and 60% were male. 81% of patients had clear cell histology, 11% had sarcomatoid differentiation, and 75% presented with de novo metastatic disease. Baseline IMDC risk is as follows: 4% favorable, 55% intermediate, and 26% poor risk with 15% unknown. 23% had bone metastases and 23% had liver metastases at baseline. Lines of therapy prior to CN was 1 line in 74% of patients, 2 lines in 25%, and 3 lines in 2%. For the line of IO therapy immediately preceding CN, 49% received nivolumab+ipilimumab, 30% received IO monotherapy, and 21% received combination IO/VEGF therapy. The median duration of therapy prior to surgery was 11.3 months (range 0.38-47.8). 28% of patients discontinued treatment after CN for observation. Best overall response prior to CN was stable disease in 25% of patients, partial response in 60%, and progressive disease in 4% with 11% unknown. Following receipt of IO-based treatment, 38% of patients exhibited downstaging from the baseline clinical T stage to the CN pathological T stage (Table). 11% of patients had no residual disease at CN. For pathologic outcomes, 85% of patients had negative margins, 75% had necrosis present, and the median tumor size at CN was 6.5 cm. The median PFS was 11.3 months and median OS was 25.7 months for the overall cohort. Conclusions: IO-based strategies demonstrate efficacy in the renal primary in patients with advanced RCC. T stage downstaging was demonstrated in 38% of patients with 11% having a complete pathologic response in the renal primary following IO administration. Biomarker studies on baseline and CN tissue will further elucidate molecular predictors of response and resistance to IO therapy.[Table: see text]

Impact of neoadjuvant immune checkpoint inhibitor therapy on primary tumor size and complexity: Correlation with surgical quality and short term oncological outcomes

390

Background:The concept of primary systemic therapy has gained increasing traction in the management of metastatic and locally advanced Renal Cell Carcinoma (RCC). Most series have evaluated the use of tyrosine-kinase inhibitors, however, with the emergence of immune checkpoint inhibitor therapy as first line agents in advanced RCC, further assessment of efficacy is warranted. We examined the effects of immunotherapy (IO) combinations on the primary tumor and consequent surgical quality and short-term oncological outcomes. Methods: We conducted a multi-center, retrospective analysis of patients with advanced/metastatic RCC having received IO followed by Radical (RN) or partial nephrectomy (PN). Primary outcome was achievement of Bifecta (composite outcome of complete resection and no 30-day post-operative complications). Predictors for achievement of Bifecta were assessed with logistic regression multivariable analysis. Secondary outcomes were change in maximal tumor dimension, RENAL nephrometry score and disease progression. Kaplan-Meier analysis was used to assess progression-free survival (PFS) for Bifecta and non-Bifecta patients. Results: We identified 52 patients with advanced RCC across 9 institutions who were eligible. The median age was 63 years and 60.4% were males. Median tumor size at diagnosis was 9.3 cm. 19.6% had T4 disease and 75% had AJCC Stage IV disease. IO treatment resulted in significant reductions in median tumor size (-25.4%; 9.7 cm vs. 7.3cm p = 0.0129) and RENAL nephrometry score (9 to 8, p = 0.032). 43 (83%) of patients underwent RN and (9) 17% had PN. Median tumor size was smaller for PN (8 vs. 4.1 cm, p < 0.001), and 30 day complication rates were higher (p = 0.024). Bifecta was achieved in 39 patients [33/42 (78.6%) RN and 6/9 (67%) PN, p = 0.264). Predictors for achievement of Bifecta were younger age (OR 1.06, p = 0.01), increasing reduction in tumor size (OR 1.187, p < 0.001), and shorter time between therapy and surgery (OR 1.07, p < 0.001). Kaplan-Meier analysis demonstrated longer median time to progression in the Bifecta-positive group compared to patients who failed to achieve Bifecta (75 vs. 30 months, p = 0.04). Conclusions: Pre-surgical therapy resulted in tumor size and complexity reduction. Tumor size reduction was predictive for achievement of Bifecta, which was associated with improved short term oncological outcomes. To our knowledge, this is the first series evaluating the effect of neoadjuvant systemic therapy on the primary tumor prior to surgical intervention.

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 single-arm, open-label, phase 2 study evaluating pacritinib for patients with biochemical recurrence after definitive treatment for prostate cancer: Blast study

TPS220

Background: Androgen deprivation therapy (ADT) achieved with gonadotropin releasing hormone (GnRH) agonist or antagonist is considered the standard of care for men with prostate cancer (PC) who develop biochemical recurrence (BCR) after definitive treatment. ADT is associated with significant adverse effects in this asymptomatic population, and hence there is an unmet need for alternate non-hormonal options. Androgen receptor (AR) and its variants (AR-V) are persistently expressed in the majority of the cells in recurrent PCs and drives PC growth. Jak2-Stat5 signaling has been shown to sustain PC cell viability and is critical for PC tumor growth. Stat5 activation in PC at the time of surgery predicts early PC recurrence. Our investigation of the molecular targets downstream of Jak2-Stat5 signaling have revealed the AR gene as a critical target, and the Jak2-Stat5 pathway represents a target to inhibit expression of diverse AR and AR-V species and thereby control of PC growth. Pacritinib (PAC) is a novel JAK2 inhibitor that suppresses wild-type Jak2 in cell-based assays and has demonstrated promising antitumor activity in myelofibrosis. We hypothesize that PAC inhibition of Jak2-Stat5 signaling will induce biochemical responses in men with recurrent PC by depleting AR and AR-V. Methods: BLAST (NCT04635059) is a single arm, open-label, phase 2 study of PAC (200mg BID) for patients with PC who underwent definitive treatment and developed BCR. Eligibility criteria include histologically confirmed PC, BCR with a PSA doubling time ≤ 9 months, PSA > 0.5 ng/mL, and serum testosterone > 150 ng/dL. 46 subjects will be enrolled with a primary objective to assess the effect of PAC on time to PSA progression. The primary endpoint is six-month PSA progression free survival per PCWG3 criteria. The null hypothesis that the median PSA-progression-free survival is six months will be tested against a one-sided alternative for the six-month PSA-progression-free survival probability exceeding 50%. Secondary endpoints include time to subsequent therapy, safety and toxicity. Exploratory endpoints include effect of PAC on geriatric domains. An interim analysis will be performed when 10 patients have been treated and followed for six months. Accrual began in July 2021. Clinical trial information: NCT04635059.

Efficacy of enfortumab vedotin in advanced urothelial cancer: Analysis from the Urothelial Cancer Network to Investigate Therapeutic Experiences (UNITE) study

BACKGROUND

Enfortumab vedotin (EV) is a novel antibody-drug conjugate approved for advanced urothelial cancer (aUC) refractory to prior therapy. In the Urothelial Cancer Network to Investigate Therapeutic Experiences (UNITE) study, the authors looked at the experience with EV in patient subsets of interest for which activity had not been well defined in clinical trials.

METHODS

UNITE was a retrospective study of patients with aUC treated with recently approved agents. This initial analysis focused on patients treated with EV. Patient data were abstracted from chart reviews by investigators at each site. The observed response rate (ORR) was investigator-assessed for patients with at least 1 post-baseline scan or clear evidence of clinical progression. ORRs were compared across subsets of interest for patients treated with EV monotherapy.

RESULTS

The initial UNITE analysis included 304 patients from 16 institutions; 260 of these patients were treated with EV monotherapy and included in the analyses. In the monotherapy cohort, the ORR was 52%, and it was >40% in all reported subsets of interest, including patients with comorbidities previously excluded from clinical trials (baseline renal impairment, diabetes, and neuropathy) and patients with fibroblast growth factor receptor 3 (FGFR3) alterations. Progression-free survival and overall survival were 6.8 and 14.4 months, respectively. Patients with a pure urothelial histology had a higher ORR than patients with a variant histology component (58% vs 42%; P = .06).

CONCLUSIONS

In a large retrospective cohort, responses to EV monotherapy were consistent with data previously reported in clinical trials and were also observed in various patient subsets, including patients with variant histology, patients with FGFR3 alterations, and patients previously excluded from clinical trials with an estimated glomerular filtration rate < 30 mL/min and significant comorbidities.

LAY SUMMARY

Enfortumab vedotin, approved by the Food and Drug Administration in 2019, is an important new drug for the treatment of patients with advanced bladder cancer. This study looks at the effectiveness of enfortumab vedotin as it has been used at multiple centers since approval, and focuses on important patient populations previously excluded from clinical trials. These populations include patients with decreased kidney function, diabetes, and important mutations. Enfortumab vedotin is effective for treating these patients. Previously reported clinical trial data have been replicated in this real-world setting, and support the use of this drug in broader patient populations.

294 Evaluation of radiographic response in the intact renal mass (intact-Rmass) to immune checkpoint inhibitor (ICI) combination regimens in patients with metastatic renal cell carcinoma (mRCC)

Background

As most of the patients previously enrolled in trials had nephrectomy before starting systemic treatment (syst-Rx), the response of the intact-Rmass to novel ICI and tyrosine kinase inhibitor (TKI) combination regimens is not well described.

Methods

A retrospective review of 227 patients with mRCC who were treated with ICI (single agent or combinations) in the 1st- or 2nd-line was conducted. Following the appropriate regulatory process, collaborators from 6 US sites collected clinical, pathological, and outcome data via chart review. Overall response was investigator-assessed for all patients with at least one post-treatment scan or evidence of clinical progression after treatment initiation. Overall radiographic response (ORR) represents any radiographic response in the metastatic disease per investigator’s assessment. To accurately assess response in intact-Rmass, 3-dimensional measurement of the intact-Rmass was performed and Rmass volume was calculated at baseline and at the time of best overall response for 1st- and 2nd-line therapy. Radiographic response in intact-Rmass is defined as >30% decrease in the Rmass volume.

Results

Median age at diagnosis was 62 years, 69% were male, 82% had clear cell histology. 15% and 12% had sarcomatoid and rhabdoid features, respectively. Overall, 82 patients (36%) had a measurable intact-Rmass while receiving syst-Rx. 63 (28%) patients never had a nephrectomy, and 10 (4%) patients had delayed nephrectomy after a good overall response to syst-Rx. 108 (48%) received ICI in 1st-line (88/108 received ipilimumab/nivolumab combination). 91 (40%), and 18 (8%) patients received TKI, or ICI+TKI in 1st-line. 161 (71%) and 86 (38%) of the patients received 2nd-line and 3rd-line therapy, respectively. 104 (46%) received ICI in 2nd-line (75/104 treated with single-agent ICI). 48 (21%), and 4 (2%) patients received TKI, or ICI+TKI in 2nd-line. Radiographic response in intact-Rmass for evaluable patients is summarized in table 1. The highest response rates in intact-Rmass were seen with ICI+TKI combinations. Higher rates of radiographic response in intact-Rmass were seen in patients treated with ICI in 1st-line compared to 2nd-line, possibly related to higher usage of ICI combinations (ipilimumab/nivolumab) in 1st-line. Overall metastatic disease response to different regimens in the 1st-line or 2nd-line was not different based on the history of nephrectomy prior to syst-Rx (table 2).

Abstract 294 Table 1

Radiographic response (≥30% decrease in volume) in the intact renal mass

Abstract 294 Table 2

Overall radiographic response (ORR) per investigator assessment

Conclusions

Higher radiographic response rates in the intact-Rmass were seen in patients treated with ICI+TKI and ICI in the 1st-line. There was no significant difference in overall metastatic disease response to 1st- or 2nd-line treatment based on the history of nephrectomy prior to syst-Rx.

Ethics Approval

Each of the 6 participating centers had their IRB approved protocol for retrospective study and data collection. Data Use Agreements were obtained for each center to share limited data set data with University of Wisconsin - Madison (IRB protocol UW17148 # 2018–0213). Final analysis was performed at University of Wisconsin.

Consent not applicable to retrospective studies.

Efficacy of anti-PD(L)1 therapy for patients (Pts) with advanced urothelial carcinoma (aUC) with primary resistance to platinum-based chemotherapy (PC)

e16515

Background: PC remains standard first-line (1L) therapy for aUC. Approximately 15% of pts exhibit primary resistance (P-R) to PC and ∼25% progress by 4 months. PD(L)1 inhibitors yield objective response rates (ORR) of ∼20% in pts with progression after PC; however, it is unclear if this benefit extends to pts with P-R to PC. We examined the efficacy of anti-PD(L)1 in pts with aUC who experienced P-R to 1L PC. Methods: We conducted a multi-institutional retrospective study of pts with aUC who experienced P-R to PC and were subsequently treated with single-agent anti-PD(L)1 therapy. Eligibility included pts with unresectable or metastatic disease diagnosed after January 1, 2017. P-R to PC was defined as radiographic progression by RECISTv1.1 within 12 weeks from initiation of PC. Pts who developed metastatic disease while receiving (neo)adjuvant PC were eligible. Clinicopathologic variables were collected. ORR to anti-PD(L)1 was the primary endpoint. Secondary endpoints included time to treatment failure (TTF, defined as time from start of anti-PD(L)1 therapy to next line of therapy, hospice or death) and overall survival (OS) were estimated using Kaplan-Meier method. Multivariate (MV) analysis using Cox regression evaluating factors associated with OS was performed. Results: Overall, 42 pts were included: 74% male, median age 65 (28-90); 79% ever smokers; 21% mixed histology; 31% received definitive locoregional therapy. Metastatic sites at diagnosis of aUC included: lymph node only (19%), liver (29%), bone (38%) and lung (33%). At diagnosis of aUC, ECOG PS was 0 in 26%, 1 in 52% and unknown in 21%. 1L PC included cisplatin (76%) and carboplatin (24%) based regimens. Anti-PD(L)1 was received either 2L (98%) or 3L (2%). Overall, ORR to anti-PD(L)1 was 17%: CR (2%), PR (14%), SD (14%), PD (57%) and unknown (12%). Of the 24 pts with PD as best response to anti-PD(L)1, only 9 (38%) received subsequent therapy. Overall, median TTF was 4.2 mo (95% CI 2.8-6.7 mo) and median OS was 7.4 mo (95% CI 4.2-11.1 mo). ORR in patients with a PDL1 combined positive score ≥ 10% (n=6) was 0%: 1 SD and 5 PD. MV analysis for OS from start of anti-PD(L)1 is shown (Table). Conclusions: P-R to PC portends a poor prognosis in pts with aUC. While a subset of patients may respond to anti-PD(L)1 therapy, the majority of pts do not derive benefit. Alternative agents, e.g. antibody drug conjugates and FGFR inhibitors, and combination-therapy should be investigated for this high risk population.[Table: see text]

Phase I study of CCW702, a bispecific small molecule-antibody conjugate targeting PSMA and CD3 in patients with metastatic castration-resistant prostate cancer (mCRPC)

TPS5094

Background: CCW702 is a novel bispecific antibody comprised of a small molecule imaging agent ligand (DUPA) with specificity for prostate specific membrane antigen (PSMA) conjugated to an anti-CD3 antibody via an unnatural amino acid. This format has the structure of an antibody drug conjugate with the activity of a CD3-engaging bispecific antibody. The design of CCW702 was leveraged to optimize the structure and function of T cell redirected cytotoxicity against PSMA-positive prostate cancer tumors in preclinical development. Methods: This is a first-in-human, open-label, multi-center phase 1 study evaluating the safety and tolerability of CCW702 when administered via subcutaneous (SC) injection in men with mCPRC. This study will be conducted in two parts: Part I, a dose escalation to determine the maximum tolerated dose (MTD) and recommended phase 2 dose (R2PD); Part II, a dose expansion to determine efficacy at the R2PD. Safety, pharmacokinetics (PK), pharmacodynamics (PD), immunogenicity, and preliminary efficacy will be evaluated. Efficacy will be assessed by change in circulating tumor cells (CTC), PSA50 response rate, and objective tumor response by RECIST v1.1. Key biomarkers include characterization of CTC, T cell phenotyping in peripheral blood, chemokines and cytokines over time, and evaluation of available tumor biopsies by IHC. Key inclusion criteria include men age ≥ 18 years with histologically or cytologically confirmed adenocarcinoma who, in the metastatic setting, have progressed on at least one novel AR-targeted therapy. Up to 1 prior chemotherapy regimen is allowed. This study will enroll 20-30 patients in Part 1 and approximately 40 patients in Part 2. The study opened in December 2019 and is currently enrolling in the dose escalation phase. Clinical trial information: NCT04077021.

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]

Talazoparib (TALA), an oral poly (ADP-ribose) polymerase (PARP) inhibitor for men with metastatic castration-resistant prostate cancer (mCRPC) and DNA damage response (DDR) alterations: Detailed safety analyses from TALAPRO-1 trial

5047

Background: PARP inhibitors have recently been approved for the treatment of mCRPC. In this Phase 2 study, we explore the safety profile of TALA in men with mCRPC with the aim of understanding how patients (pts) with adverse events (AEs) were managed during the trial. Methods: TALAPRO-1 (NCT03148795) is a single-arm, open-label, phase 2 study of TALA in pts with progressive mCRPC, measurable soft tissue disease, and DDRm likely to sensitize to PARPi ( ATM, ATR, BRCA1/2, CHEK2, FANCA, MLH1, MRE11A, NBN, PALB2, RAD51C), who received ≥1 taxane-based chemotherapy and progressed on ≥1 novel hormonal therapy (enzalutamide/abiraterone). The primary objective was confirmed objective response by central independent review; the assessment of safety included AEs, incidence of dose modifications and of permanent treatment discontinuation due to AEs, and clinical laboratory tests. Results: In the TALA-treated population (1 mg/daily; n=127), 95.3% (121/127) experienced all-causality AEs. The most common (≥15%) hematologic AEs were anemia (any grade, 48.8%; G3, 30.7% [no G4 events]), thrombocytopenia (all grade, 18.9%; G3/4, 8.7%), and neutropenia (all grade, 16.5%, G3, 7.9% [no G4]). Median time from first dose of TALA to onset of first episode of G≥3 anemia, neutropenia, and thrombocytopenia was 56, 48, and 17 days, respectively. G3 anemia lasted a median of 7 days, G3 neutropenia lasted a median of 12 days, G3 and G4 thrombocytopenia lasted a median of 8 and 11 days, respectively. Hematologic AEs typically occurred during the first 4–5 months of TALA treatment and were managed by dose modifications and supportive care. 34.6% of pts received a blood transfusion product, and most transfusions occurred when hemoglobin was between 7.0–10.0 g/dL. Overlapping G3/4 hematologic AEs were infrequent on TALA (anemia + neutropenia 4.7%; anemia + thrombocytopenia 5.5%; neutropenia + thrombocytopenia 1.6%). In pts who had anemia, 12.6% also had fatigue; in those with thrombocytopenia, 4.7% had a subsequent bleeding event; in those with neutropenia, 1.6% had an overlapping infection. The most common non-hematologic AEs (≥15%) were nausea (any grade, 33.1%; G3/4, 2.4%), decreased appetite (any grade, 28.3%; G3/4, 3.1%), and asthenia/fatigue (any grade, 23.6%/19.7%; G3/4, 3.9%/1.6%). In the treated population, dose reduction of TALA due to all-causality AE occurred in 33 pts (26.0%). Treatment discontinuation due to all-causality AEs was low and occurred in 15 pts (11.8%); the most frequent (≥2 pts) AEs leading to discontinuation of TALA were back pain and platelet count decrease (each, 1.6% [2/127 pts]). There were no treatment-related deaths. Conclusions: A manageable safety profile and durable antitumor effects were observed with TALA in men with heavily pretreated mCRPC in this phase 2 study. Clinical trial information: NCT03148795.

Pembrolizumab plus enzalutamide for enzalutamide-resistant metastatic castration-resistant prostate cancer (mCRPC): Updated analyses after one additional year of follow-up from cohorts 4 and 5 of the KEYNOTE-199 study

5042

Background: KEYNOTE-199 (NCT02787005) is a multicohort phase 2 study to evaluate pembrolizumab (pembro) in mCRPC. A previous analysis of patients with RECIST-measurable (cohort 4 [C4]) or bone-predominant nonmeasurable (cohort 5 [C5]) disease who were chemotherapy-naive and had progression while on enzalutamide (enza) found that pembro + enza showed antitumor activity and manageable safety. Long-term outcomes are of interest with immunotherapy; hence, updated efficacy and safety data after an additional 1 year of follow-up are presented. Methods: Pts were eligible if they had resistance to enza after prior response. Prior treatment with abiraterone was allowed. Pts received pembro 200 mg Q3W for up to 35 cycles + enza QD until progression, unacceptable toxicity, or withdrawal. Primary end point was ORR per RECIST v1.1 by blinded independent central review (BICR) in C4. Secondary end points were DOR (C4), and DCR, rPFS, OS and safety (both cohorts). Results: 126 pts (C4, 81; C5, 45) were treated. Median age was 72 years (range 43-92), 32.5% had visceral disease and 87.3% previously received ≥6 mo of enzalutamide; 121 pts (96.0%) discontinued, most because of progressive disease. Median (range) time from enrollment to data cutoff was 31.7 mo (23.1-37.1) in C4 and 35.5 mo (22.9-37.3) in C5. In C4, confirmed ORR was 12.3% (95% CI 6.1-21.5) (2 CRs, 8 PRs); median (range) DOR was 8.1 mo (2.5+ to 15.2), and 62.5% had a response ≥6 mo (Kaplan-Meier estimate). Additional efficacy analyses are outlined in the table. A total of 27.2% and 28.9% of pts in C4 and C5, respectively, experienced grade ≥3 treatment-related adverse events. Two pts in C4 died of immune-related AEs (Miller Fisher syndrome and myasthenia gravis). Incidence of any-grade (34.1%) and grade 3 or 4 (5.6%) rash, regardless of relatedness to treatment, was higher than previously reported for individual agents but manageable with standard-of-care treatments; 2 pts discontinued because of rash. Conclusions: After an additional 1 year of follow-up, pembro + enza continued to show antitumor activity and a manageable safety profile in pts with mCRPC who became resistant to enza. The treatment combination is being further evaluated in the ongoing phase 3 KEYNOTE-641 trial (NCT03834493). Clinical trial information: NCT02787005. [Table: see text]

A phase 2 study of cabozantinib in combination with atezolizumab as neoadjuvant treatment for muscle-invasive bladder cancer (HCRN GU18-343) ABATE study

TPS4591

Background: ABACUS and PURE-01 trials demonstrated the activity of single agent atezolizumab and pembrolizumab respectively as neoadjuvant therapy for muscle invasive urothelial carcinoma (MIUC). However, downstaging to non-muscle invasive disease was noted in only 50 percent of patients. Resistance to programmed death (PD)- 1/L-1 antibodies is likely to include factors such as impaired dendritic cell maturation/function, infiltration of T-Regs and myeloid derived suppressor cells, impaired T-cell priming and T-cell trafficking in tumors. Cabozantinib is a tyrosine kinase inhibitor which targets MET, AXL, MER, Tyro3 and VEGFR2. Cabozantinib has a unique immunomodulatory profile and has demonstrated clinical activity as monotherapy and in combination with PD-1/L1 antibodies in various solid tumors including UC, renal cell cancer, castrate- resistant prostate cancer, and non-small cell lung cancer. We hypothesize that the combination of cabozantinib and atezolizumab as neoadjuvant therapy for MIUC would improve rates of pathologic downstaging compared to single-agent checkpoint inhibitors. Methods: ABATE(NCT04289779) is an open-label, single arm, multi-center study to assess the efficacy and safety of cabozantinib with atezolizumab as neoadjuvant therapy for cT2-T4aN0/xM0 MIUC. An estimated 38 patients will be enrolled and receive cabozantinib 40 mg PO daily with atezolizumab 1200mg every 3 weeks for a total duration of 9 weeks followed by radical cystectomy. Adults (≥18 years) with resectable UC who are either cisplatin-ineligible or decline cisplatin are eligible. Patients are required to have an ECOG PS of 0-2 and provide tumor tissue for PD-L1 analysis. UC should be predominant component (≥ 50%). Previous systemic anticancer therapies for MIUC are not permitted. CT/MRI will be performed before investigational therapy and cystectomy. Primary endpoint is pathologic response rate defined as the absence of residual muscle-invasive cancer in the surgical specimen ( < pT2). Secondary endpoints are safety and toxicity, pathologic complete response rate and event-free survival. Exploratory end points include patient-reported outcomes and outcome associations with biomarkers. Accrual began May 2020. Clinical trial information: NCT04289779.

Long-Term Outcomes of Dose-Escalated Pelvic Lymph Node Intensity-Modulated Radiation Therapy (IMRT) With a Simultaneous Hypofractionated Boost to the Prostate for Very High-Risk Adenocarcinoma of the Prostate: A Prospective Phase II Clinical Trial

PURPOSE

There remains limited data as to the feasibility, safety, and efficacy of higher doses of elective radiation therapy to the pelvic lymph nodes in men with high-risk prostate cancer. We conducted a phase II study to evaluate moderate dose escalation to the pelvic lymph nodes using a simultaneous integrated boost to the prostate.

METHODS AND MATERIALS

Patients were eligible with biopsy-proven adenocarcinoma of the prostate, a calculated lymph node risk of at least 25%, Karnofsky performance scale ≥70, and no evidence of M1 disease. Acute and late toxicity were prospectively collected at each follow-up using Common Terminology Criteria for Adverse Events version 4.0 (CTCAE v4.0). The pelvic lymph nodes were treated to a dose of 56 Gy over 28 fractions with a simultaneous integrated boost to the prostate to a total dose of 70 Gy over 28 fractions using intensity-modulated radiation therapy.

RESULTS

Thirty patients were prospectively enrolled from October 2010 to August 2014. Median patient age was 70 years (57-83), pretreatment prostate-specific antigen was 11.5 ng/mL (3.23-111.5), T stage was T2c (T1c-T3b), and Gleason score was 9 (6-9). CTCAE v4.0 rate of any grade 1 or 2 genitourinary and gastrointestinal toxicity were 55% and 44%, respectively, and there was 1 reported acute grade 3 genitourinary and gastrointestinal toxicity, both unrelated to protocol therapy. With a median follow-up of 6.4 years, the biochemical failure free survival rate was 80.2%, and mean biochemical progression free survival was 8.3 years (95% confidence interval [CI], 7.2-9.4). The prostate cancer specific survival was 95.2%, and mean prostate cancer specific survival was 8.7 years (95% CI, 8.0-9.4). Five-year distant metastases free survival was 96%. Medians were not reached.

CONCLUSIONS

In this single arm, small, prospective feasibility study, nodal radiation therapy dose escalation was safe, feasible, and seemingly well tolerated. Rates of progression free survival are highly encouraging in this population of predominately National Comprehensive Cancer Network very high-risk patients.

Change in neutrophil to lymphocyte ratio (NLR) as a predictor of treatment failure in renal cell carcinoma patients: Analysis of the IROC (Investigating RCC Outcomes) cohort

344

Background: IROC is an expanding multi-institution collaborative database which includes socioeconomic, genomic, pathologic, clinical and laboratory data in metastatic RCC patients (pts), primarily in the modern setting. Elevated baseline NLR is now an established poor prognostic factor in renal cell carcinoma (RCC) but currently has limited practical use. We hypothesized that an increase in NLR of 3 or more (NLR Failure) at 2 months on therapy could be a predictor of eventual treatment failure and shorter overall survival and thus augment the utility of this marker. Methods: Patients with complete data on NLR at time = 0 and +2 months of therapy were analyzed. Information on comorbidities, previous therapy, demographics were collected for adjusted analysis. NLR failure was defined as an increase of 3 or more compared to baseline NLR. Cox proportional hazard models were used to analyze the risk of progression and death with NLR failure at 2 months (+/- 2 weeks). Kaplan Meier graphs were constructed to trace survival functions for PFS and OS by NLR. Results: Among 165 pts; 121 were eligible (Table). NLR failure at 2 months was associated with a highly statistically significant increase in the risk of death in < 1 year (HR 6.82, 95% CI [3.16-14.70], p<0.001). In a model adjusted for NLR change, the value of baseline NLR to predict OS <1 year was non-significant (HR 1.02, p = 0.65). Similarly, NLR failure increased the risk of treatment failure in less than 6 months (HR 4.83 95% CI [ 2.29-10 .19], p<0.001), while baseline NLR did not predict it (HR 1.03, p = 0.34). These findings were unaffected by immunotherapy vs TKI therapy. NLR failure at 2 months had a 78% (11/14) positive predictive value for survival <1 year and 86% (12/14) [p=.0001] for treatment failure in 6 months. Conclusions: In this multi-institutional cohort of RCC pts; an increase in NLR of 3 or more at 2 months following therapy start predicts for an increasing risk of death and impending treatment failure with a high PPV. The prognostic value of baseline NLR is non-significant when adjusting for NLR change. NLR failure should be validated in prospective studies and could have clinical utility in management of RCC pts. [Table: see text]

Phase II clinical study of concurrent durvalumab and radiation therapy (DUART) followed by adjuvant durvalumab in patients with localized urothelial cancer of bladder: Results for primary analyses and survival. BTCRC-GU15-023

398

Background: Bladder cancer (BC) patients (pts) who are cisplatin ineligible/unfit for surgery, or locally advanced and unresectable have limited treatment options. DUART investigates if the combination of radiation therapy (RT) and checkpoint inhibitor, durvalumab (durva) is safe and effective in these pts. We recently reported that the combination was safe, tolerable and disease control rate (DCR) was 92% post durvaRT. Here we present interim efficacy data of our phase II study. Methods: Pts with pure or mixed urothelial bladder cancer (T2-4 N0-2 M0) were enrolled if their tumor was unresectable (35%), were unfit for surgery (50%) and/or cisplatin ineligible (89%). Primary endpoints: a) PFS at 1-yr b) DCR post adjuvant durva; Secondary endpoints: a) CR post durvaRT b) median PFS c) median OS. Pts were treated with durva (1500mg) Q4 wks x2 doses along with definitive RT (64.8Gy, 36 fractions over 7 wks) to the bladder and involved nodes followed by adjuvant durva Q4 wks x 1 yr. Response was evaluated with CT scan and cystoscopy+biopsy. Sample size was based on assumption that this regimen would increase 1 yr PFS by 25% compared to RT alone (50% to 75%); we assumed DCR of 75%. A total of 26 pts were needed to reach a statistical power of at least 80% at one-sided alpha of 5% and to allow for 10% drop out rate. Results: Twenty-six pts (19 males, 7 females) were enrolled, median age 74 yr (51-94). Sixty two percent of pts had >T2 disease, 31% had positive lymph nodes; 62% with unresectable tumor or were unfit for surgery due to comorbidities. At data cut off (9/30/2020) 20/26 pts were evaluable for DCR post adjuvant durva (3 pts with CR post durvaRT, did not get adjuvant therapy; 1 pt withdrew after 3 cycles for adjuvant durva and was on f/u with unconfirmed CR; 2 pts are still on adjuvant durva) and 25/26 for PFS and all 26 pts for OS. Post completion of adjuvant durva, DCR was seen in 70 % (14/20 with 10 CR; 3 PR; 1 SD; 6 PD). One-year probability of PFS was 73% (95% CI 56.4%, 94.4%), median PFS was 18.5 months. One-year OS probability was 83.8% (95% CI 70.4%, 99.7%) with two-year OS probability of 76.8 (95% CI 60.2%, 98%). Median OS has not been reached. We did not observe any correlation between clinical outcome and baseline tumor PD-L1 expression. Conclusions: DurvaRT followed by adjuvant durva demonstrated promising efficacy with 1-year PFS probability of 73%, 1- year OS probability of 83.8% and DCR of 70% in MIBC and locally advanced BC pts with comorbidities. Results will be updated prior to the final presentation. Efficacy was also seen in node (+) pts which led to the design of prospective randomized NCTN study. Induction chemo followed by chemo+durvaRT+ adjuvant durva vs. chemoRT combination is being evaluated in the ongoing EA8185 clinical trial (ECOG-ACRIN/NRG study) for node (+) BC pts. Clinical trial information: NCT02891161.

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]

Treatment response in the intact primary renal mass (P-Rmass) and its relationship to the overall response to treatment in patients with metastatic renal cell carcinoma (mRCC)

329

Background: With the approval of more effective systemic treatments (syst Rx) such as tyrosine kinase inhibitors (TKI) and immune checkpoint inhibitors (ICI), the impact of cytoreductive nephrectomy (CN) on response to Rx and survival remains unknown. The majority of patients (pts) previously enrolled in clinical trials have had radical nephrectomy (RN) or CN prior to syst Rx. Therefore, the response of the P-Rmass to ICIs and the effect of intact P-Rmass on response to syst Rx is not well described. Methods: A retrospective review of 209 pts with mRCC who were treated with ICI in the first or second-line was conducted. Following the appropriate regulatory process, collaborators from 5 US sites collected clinical, pathological, and outcome data via chart review. The response was investigator-assessed for all pts with at least one post-treatment scan or evidence of clinical progression after treatment initiation. Overall radiographic response (ORR) includes complete response (CR) and radiographic response (Rad-resp) to treatment. Disease control rate (DCR) includes CR, Rad-resp, and stable disease. Results: Median age at diagnosis was 63 yrs and 69% were male. 102 pts (49%) had localized disease at diagnosis and underwent radical or partial nephrectomy, 3 (1%) had ablation/radiation of P-Rmass, 26 (12%) had CN, 9 (4%) had CN after an excellent response to syst Rx, 12 (6%) had a previous nephrectomy but developed a new Rmass (measurable target lesion), and 57 (27%) did not have CN and had an intact P-Rmass. 176 (84%) pts had clear cell histology. 27 (14%) and 23 (12%) had known sarcomatoid and rhabdoid features, respectively. Overall, 77 (37%) pts had a measurable Rmass while receiving syst Rx. 84 (40%), 93 (45%), and 10 (5%) pts received ICI (Ipilimumab/Nivolumab or Nivo), TKI, or Pembrolizumab/Axitinib in the first-line. 143 (68%) and 70 (33%) pts received second- and third-line treatment. 103 (72%) and 28 (19%) pts received ICI and TKI in the second-line, respectively. The best ORR and the Rad-resp in the intact P-Rmass in evaluable pts are summarized in the table below. ORR to ICI in the first or second-line were numerically higher in pts with an intact P-Rmass compared to pts who had nephrectomy, but this difference was not statistically significant (p= .38 and .35 respectively). Conclusions: The intact P-Rmass had a good response (62-70%) to the first-line syst Rx. Although the overall Rad-resp rates to ICI are numerically higher in pts with intact P-Rmass, this difference was not statistically significant. [Table: see text]

Outcomes With First-Line PD-1/PD-L1 Inhibitor Monotherapy for Metastatic Renal Cell Carcinoma (mRCC): A Multi-Institutional Cohort

Introduction: The treatment landscape of metastatic renal cell carcinoma has advanced significantly with the approval of combination regimens containing an immune checkpoint inhibitor (ICI) for patients with treatment-naïve disease. Little information is available regarding the activity of single-agent ICIs for patients with previously untreated mRCC not enrolled in clinical trials. Methods: This retrospective, multicenter cohort included consecutive treatment-naïve mRCC patients from six institutions in the United States who received ≥1 dose of an ICI outside a clinical trial, between June 2017 and October 2019. Descriptive statistics were used to analyze outcomes including objective best response rate (ORR), progression-free survival (PFS), and tolerability. Results: The final analysis included 27 patients, 70% men, median age 64 years (range 42-92), 67% Caucasian, and 33% with ECOG 2 or 3 at baseline. Most patients had intermediate risk (85%, IMDC) with clear cell (56%), papillary (26%), unclassified (11%), chromophobe (4%), and translocation (4%) RCC. All patients had evidence of metastatic disease involving the lungs (59%), lymph node (41%), CNS (19%), liver (11%), adrenal gland (11%), and bone (11%). The median time on ICI was 3.1 (0.1-26.8) months, and the median PFS was 6.3 (95% CI, 0-18.6) months. Among the 21 patients with an evaluable response, the best ORR was 33%, including two complete responses and five partial responses. The ORR was 29% (n = 1 complete response, n = 5 partial response) in clear cell and 5% (n = 1 complete response) in non-clear cell RCC. Adverse events (AEs) of any cause were reported in 37% and included fatigue (11%), dermatitis (11%), diarrhea (7%), and shortness of breath (7%). Significant AEs (30%) included shortness of breath (7%), acute kidney injury (4%), dermatitis (4%), Clostridium difficile infection (4%), cerebrovascular accident (4%), and fatigue (7%). Three patients discontinued therapy due to grade 4 AEs. Conclusions: In this multi-institutional case series, single-agent ICI demonstrated objective responses and was well tolerated in a heterogeneous treatment-naïve mRCC cohort. ICI monotherapy is not the standard of care for patients with mRCC, and further investigation is necessary to explore predictive biomarkers for optimal treatment selection in this setting.