Safety, Immunologic, and Clinical Activity of Durvalumab in Combination with Olaparib or Cediranib in Advanced Leiomyosarcoma: Results of the DAPPER Clinical Trial

PURPOSE

Non-inflamed (cold) tumors such as leiomyosarcoma do not benefit from immune checkpoint blockade (ICB) monotherapy. Combining ICB with angiogenesis or PARP inhibitors may increase tumor immunogenicity by altering the immune cell composition of the tumor microenvironment (TME). The DAPPER phase II study evaluated the safety, immunologic, and clinical activity of ICB-based combinations in pretreated patients with leiomyosarcoma.

PATIENTS AND METHODS

Patients were randomized to receive durvalumab 1,500 mg IV every 4 weeks with either olaparib 300 mg twice a day orally (Arm A) or cediranib 20 mg every day orally 5 days/week (Arm B) until unacceptable toxicity or disease progression. Paired tumor biopsies, serial radiologic assessments and stool collections were performed. Primary endpoints were safety and immune cell changes in the TME. Objective responses and survival were correlated with transcriptomic, radiomic, and microbiome parameters.

RESULTS

Among 30 heavily pretreated patients (15 on each arm), grade ≥ 3 toxicity occurred in 3 (20%) and 2 (13%) on Arms A and B, respectively. On Arm A, 1 patient achieved partial response (PR) with increase in CD8 T cells and macrophages in the TME during treatment, while 4 had stable disease (SD) ≥ 6 months. No patients on Arm B achieved PR or SD ≥ 6 months. Transcriptome analysis showed that baseline M1-macrophage and B-cell activity were associated with overall survival.

CONCLUSIONS

Durvalumab plus olaparib increased immune cell infiltration of TME with clinical benefit in some patients with leiomyosarcoma. Baseline M1-macrophage and B-cell activity may identify patients with leiomyosarcoma with favorable outcomes on immunotherapy and should be further evaluated.

The survival outcomes of metastatic non-clear cell renal cell carcinoma in the immunotherapy era: Princess Margaret Cancer Centre (PMCC) experience

636

Background: Immunotherapy (IO) with or without targeted therapy (TT) is the standard treatment for patients (pts) with advanced clear cell renal cell carcinoma. The evidence to support their use in metastatic non-clear cell renal cell carcinoma (nccRCC) is based on smaller prospective trials and retrospective analyses. Here, we report the survival outcomes of pts with nccRCC treated with IO containing regimens or TT. Methods: This retrospective survival analysis was performed in metastatic nccRCC pts treated with IO and/or TT at the PMCC, Toronto between 2002 and 2021. Demographics, disease characteristics and survival outcomes were collected. Overall survival (OS) and progression-free survival (PFS) were calculated using the Kaplan-Meier method (log-rank). Chi-square and fisher’s exact tests were used to evaluate response rates where appropriate. Interaction between variables was estimated using Cox proportional hazards. Results: We identified 530 metastatic RCC pts, of these 69 (13%) were nccRCC treated either with an IO containing regimen or TT. Among nccRCC pts, 42 (60.9%) had papillary subtype, 10 (14.5%) chromophobe, 14 (20.3%) unclassified, and 3 (4.3%) had an XP translocation. Median age was 54 years (range: 26-75) and 48 (69.5%) were male. Overall, as per the IMDC score, 15 (21.7%), 41 (59.5%) and 13 (18.8%) pts were categorized as good, intermediate and poor risk, respectively. Median follow-up was 116 months (95%CI: 30.8-201.1 months). Pts received sunitinib (n=41), ipilimumab plus nivolumab (n=8), sorafenib (n=5), savolitinib (n=3), pembrolizumab (n=3), pazopanib (n=2), temsirolimus (n=2), pembrolizumab plus axitinib (n=1), and other TT (n=4) in the first line treatment. Everolimus (n=13), nivolumab (n=7), sunitinib (n=7), axitinib (n=2), cabozantinib (n=2), chemotherapy (n=2), pembrolizumab plus axitinib (n=1), and other TT (n=2) were given in the second line treatment. The survival outcomes and responses are shown in the table. There was no interaction between age, gender, IMDC, RCC subtypes and survival outcomes. Conclusions: While the number of pts included in our retrospective review was small, our analysis suggested that pts with metastatic nccRCC have improved survival outcomes with IO containing regimens. Validation in a prospective dataset is required before widespread clinical utilization and many trials are currently ongoing. [Table: see text]

A retrospective review of primary prophylaxis with granulocyte-colony stimulating factor (G-CSF) for patients with genitourinary malignancies receiving chemotherapy during the COVID-19 pandemic and implications for the future

115

Background: To mitigate the risks of chemotherapy associated neutropenia, during the COVID-19 pandemic, all genitourinary (GU) cancer patients treated with chemotherapy at the Princess Margaret Cancer Centre (PMCC) were offered primary prophylaxis with GCSF. We hypothesize that this reduced rates of febrile neutropenia, hospitalizations, healthcare costs and improved overall outcomes, compared to GU cancer patients treated with chemotherapy without GCSF in the 2 years prior to the pandemic. Methods: We performed a retrospective review of GU cancer patients, receiving curative or palliative intent chemotherapy, with or without primary GCSF prophylaxis between January 2018 and June 2022. GCSF was given either as a single dose or as consecutive doses post chemotherapy. Main outcomes were incidence of febrile neutropenia, hospitalization, health care expenditures as well as disease specific outcomes. Results: Overall, 248 patients with prostate cancer (44%), urothelial cancers (33%) germ cell (21%), and rare GU cancers (4%) were identified. Median age was 70 (range 19-91), 92% were male, 65% were ECOG 0/1. Treatment intent was neoadjuvant (13%), adjuvant (20%), or palliative (67%). Main regimens used were docetaxel, cabazitaxel, carboplatin, cisplatin/etoposide, gemcitabine/cisplatin and BEP. Median follow-up was 10.5 months (0.23-52.3 months). A total of 206/248 received primary GCSF prophylaxis. During chemotherapy, the median white blood cell levels were higher in the GCSF group compared to the non-GCSF group (14.1*10*9/L vs 2.90*10*9/L, p<0.0001); and neutropenia rates were markedly lower (2% vs. 93%, P=<0.0001). Hospital admission rates were significantly lower in G-CSF users compared to non-users (19% vs. 69%, P<0.0001). Symptomatic disease progression 13% was the leading cause of admission in the G-CSF group. Infectious causes such as UTI, pneumonia, COVID-19, and sepsis were seen in only 12% of the G-CSF group compared to 31% in the non-users. G-CSF was generally well tolerated with just 0.97% discontinuing G-CSF. Conclusions: During the COVID-19 pandemic, primary prophylactic G-CSF use in GU cancer patients, undergoing chemotherapy significantly lowered rates of both febrile neutropenia and hospitalizations and could be a cost-effective strategy in this patient population that warrants further study.

Is there a role for surgery after chemotherapy in recurrent/metastatic adrenal cortical cancer (ACC)?

5092

Background: ACC is a rare endocrine malignancy. Patients with metastatic disease at diagnosis are often treated palliatively with systemic therapy. It is unclear if neoadjuvant cytoreduction with chemotherapy can render metastatic or previously resected but locally recurrent patients become surgical candidates and impact overall survival (OS). Methods: A retrospective single institution review (2002-2019) of metastatic ACC patients was performed. Descriptive statistics were used and OS was estimated by Kaplan-Meier method. Results: Out of 84 patients with metastatic ACC [30 (20.7%) upfront and 54 (37.2%) after definitive therapy], 51 received systemic therapy with mitotane and etoposide-doxorubicin-cisplatin (EDP) as standard 1st line regimen and varied subsequent lines of therapy. Two patients were excluded as they were lost to follow-up. Among the included 49 patients, 29 were females (59.2%) and 26 patients (53.1%) had functional tumors at baseline. Out of 33 patients who had information available on tumor grade, 26 (78.8%) were high grade. Nine pts (18.4%) underwent surgery after receiving systemic therapy (eight after EDP in first line and one after pembrolizumab in third line). These patients were younger (median age 39 years compared to 52.5 years for those receiving only chemotherapy), had locally recurrent disease (all nine patients) with four having evidence of progressive liver metastasis. Median number of EDP cycles delivered before surgery was 4 (range 3-7). The patient who underwent surgery after pembrolizumab received nine cycles of preoperative pembrolizumab. Five pts (55.5%) had partial response, three (33.3%) had disease progression and one (11.1%) had stable disease prior to surgery. Patients underwent surgery after a mean interval of 3.1 months (m) (1.1-5.1) after systemic therapy. Six patients had no evidence of disease (NED) (five with disease limited to adrenal bed) after surgery. Eight out of nine patients recurred after surgery with a median time of 6.1 m (4.4-7.8). The median OS for the entire cohort was 26 m (95% CI 22.3-35.2). This was not significantly better for patients undergoing surgery [median OS 31.2 m (95% CI 21.4-63.3) vs 24.7 m (95% CI 17.7-35.2) p = 0.48]. Patients rendered NED after surgery had numerically better OS than those with residual disease or those receiving only chemotherapy [median OS 39.6 m (24.8.-NR), vs 23.5 m (21.4-NR) vs 24.7 m (17.7-35.2), p = 0.271]. Higher Ki-67 predicted for inferior OS in the entire cohort with no effect of age, gender, tumor grade or functional status. Conclusions: Attempting to downstage patients with metastatic or locally recurrence with systemic therapy does not seem to prolong OS in patients with ACC. Selected patients with limited disease burden, who can be rendered disease free by surgery, may be suitable for this approach.

Phase 1b study of weekly split-dose selinexor in soft tissue sarcoma (STS)

11563

Background: Selinexor has demonstrated clinical activity in a variety of tumors including STS. Selinexor dosing at 60mg twice a week or 80mg once a week in later phase trials was associated with gastrointestinal and hematologic toxicities requiring frequent dose interruption and reduction. Preclinical in vivo studies show that selinexor use in a split-dose regimen or sustained-release formula is associated with less toxicity. This phase 1b study aimed to evaluate the safety and tolerability of split-dose selinexor in patients (pts) with advanced STS. Methods: Eligible pts with advanced STS of any histologic subtype, and ECOG performance status (PS) ≤ 1 were treated with split-dose selinexor (40mg, 20mg, 20mg in the morning, afternoon, and evening, respectively) on days 1, 8, 15 and 22 of a 28-day cycle, until unacceptable toxicity or disease progression. Antiemetic prophylaxis (oral dexamethasone and ondansetron) was given to all pts. The primary endpoint was the rate of grade ≥ 3 treatment-related adverse events (TRAE) by CTCAE v5.0. The secondary endpoint was assessment of quality of life (QoL) using the EORTC QLQ-c30 tool v3. Descriptive analyses of Global Health Status (GHS) QoL scores at screening (baseline) and cycle 2 day 1 (C2D1) were performed. Radiologic tumor assessments (by RECIST v1.1) were performed every 8 weeks while on treatment. Results: Nineteen pts [12 female and 7 male; ECOG 0/1, 8/11; median age 61 years (range 41 – 83)] were enrolled. The most frequent of 12 STS subtypes was leiomyosarcoma (n = 7, 37%). Among 18 patients evaluable for toxicity, there were no grade ≥ 3 TRAE. The most common grade ≤ 2 TRAE were dysgeusia (n = 11, 61%), nausea (n = 11, 61%), fatigue (n = 10, 56%) and vomiting (n = 10, 56%). Grade ≤ 2 hematologic TRAE were thrombocytopenia (n = 6, 33%), neutropenia (n = 4, 22%) and anemia (n = 1, 6%). Dose reduction was required in 3 pts (17%) due to intolerable grade 2 TRAE (fatigue, nausea, thrombocytopenia). No serious adverse event due to selinexor was noted. QoL scores were evaluable for 15 pts. The mean (± SEM) change in GHS QoL score from baseline to C2D1 was -10.6 (± 4.8). Among 16 pts evaluable for radiologic response, the best response was stable disease (SD) in 10 pts (63%), and progressive disease (PD) in 6 pts (37%). Durable clinical benefit (SD for > 16 weeks) was seen in 5 pts (31%; 95%CI 11.0 – 58.7%) The median PFS was 3.6 months (95%CI 1.7 – 7.3). Conclusions: Split-dose selinexor was well tolerated in this heterogeneous group of pts with advanced STS and warrants further interrogation. Updated toxicity, safety, efficacy and QoL data will be presented at the meeting. Clinical trial information: NCT04811196.

Survival outcomes of metastatic renal cell carcinoma (mRCC) with sarcomatoid differentiation (SD): A single-institutional experience and literature meta-analysis

332

Background: Patients (pts) with mRCC with SD have unfavorable outcomes and poor prognosis due to aggressive tumor behavior. Chemotherapy and targeted treatment are often of little benefit. However, recent studies have shown a survival benefit of immunotherapy (IO). Here, we report survival outcomes of pts with mRCC with SD treated with first line IO or chemotherapy or targeted treatment. In addition we performed a meta-analysis of recent practice changing phase III, IO trials in mRCC. Methods: This retrospective survival analysis was performed in pts with mRCC with SD treated with IO or non-IO treatment at Princess Margaret Cancer Centre (PM), Toronto. Demographics, disease characteristics and survival outcomes were collected. Progression free survival (PFS), and overall survival (OS) were calculated using the Kaplan-Meier method (log-rank). PFS and OS hazard ratios (HR) were calculated using cox proportional hazards model. We identified the major, practice changing clinical trials that reported survival outcomes of mRCC with SD treated with IO and performed a random-effects meta-analysis of HR for PFS and OS. We compared these pooled results to our single institution experience. Results: We identified 474 pts diagnosed with mRCC at PM between 2002 and 2019. In total, 44 (9.3%) pts had mRCC with SD who were treated with IO or non-IO. Of these, 29 (65.9%) pts had pure SD and 15 (34.1%) pts had mixed rhabdoid and SD features. Median age was 59.6 years (36-78) and 33 (75%) were male. Overall, as per the IMDC score, 3(6.8%), 21(47.7%) and 20(45.5%) pts were categorized as good, intermediate, and poor risk, respectively. Eight (18.2%) pts were treated with IO as first line of treatment, and 36 (81.8%) pts received non-IO. With a median follow up of 64.8 months (range, 45.7-83.8 months), the median OS for the whole mRCC with SD cohort was 15.6 months (95% CI: 8.6-22.5). The median OS in all pts treated with IO vs non-IO was not reached vs 10.3 months (95%CI: 1.49-19.1 months; p = 0.005), respectively. The HR for OS was 0.1 (95%CI: 0.01-0.78; p = 0.023) favoring IO receipt. The median PFS in all pts treated with IO vs non-IO was 24 months (95%CI: non-estimable) vs 5.4 months (95%CI: 2.9-7.8 months; p = 0.021), respectively. The HR for PFS was 0.3 (95%CI: 0.11-0.89; p = 0.03) favoring IO receipt. We identified through meta-analysis five phase III clinical trials reporting PFS and OS in pts with mRCC with SD who received IO. The overall HR for OS and PFS for the total cohort were 0.55 (95%CI: 0.41-0.74), and 0.53 (95%CI: 0.42-0.67), respectively. Conclusions: Our meta-analysis has confirmed the benefit of IO agents in mRCC with SD. While the numbers included in this retrospective review were small, they have provided real world corroboration of the trial findings. Pts with mRCC and SD benefit from IO treatment, which should be considered the standard of care for these patients.

The survival outcomes of the metastatic renal cell carcinoma with rhabdoid differentiation in immunotherapy era: Princess Margaret Cancer Center experience

333

Background: Patients (pts) diagnosed with metastatic renal cell carcinoma (mRCC) with rhabdoid differentiation (RD) have a poor prognosis due to aggressive tumor behavior and inherent treatment resistance to targeted therapies. However, recent data has demonstrated the survival benefit of immunotherapy (IO) in mRCC. Here, we report survival outcomes of pts with mRCC with RD treated with targeted therapy and or IO. Methods: This retrospective survival analysis was performed in pts with mRCC and RD treated with targeted treatment and IO at Princess Margaret Cancer Centre (PM), Toronto. Demographics, disease characteristics and survival outcomes were collected. Overall survival (OS) was calculated using the Kaplan-Meier method (log-rank). OS hazard ratio (HR) were calculated using cox proportional hazards model. IBM SPSS Statistics v26 was used to conduct statistical analyses. Results: We identified 474 pts diagnosed with mRCC at PM between 2002 and 2019. A total of 57 (12%) pts diagnosed with mRCC had RD and were treated with targeted and or IO agents. Of these, 42 (73.7%) pts had pure RD and 15 (26.3%) pts had mixed RD and sarcomatoid features. Median age was 62 yrs (35-86yrs) and 42 (73.7%) were male. Overall, as per the IMDC score, 5(8.8%), 27(47.4%) and 25(43.8%) pts were categorized as good, intermediate, and poor risk, respectively. In total, 34 (59.6%) pts were treated with targeted therapy only during their first and second line treatment course and 23 (40.4%) pts received IO alone or in combination with targeted treatment in the first or second line. With a median follow up of 53.4 months (range, 38.3-68.4 months), the median OS for the whole mRCC with RD cohort was 23.1 months (95% CI: 14.6-31.5). The median OS in all pts treated with targeted therapy only vs IO receipt was 13.1 months (95%CI: 5.4-20.8 months) vs not reached; p = 0.026, respectively. HR for OS was 0.44 (95%CI: 0.22-0.93; p = 0.03) favoring IO receipt. Conclusions: While the number of pts included in our retrospective review was small, our analysis has suggested that pts with mRCC and RD have poor survival outcomes that may be improved with IO treatment. RD is a histopathological feature that could identify pts who may benefit from IO therapy. Further analysis is needed to explore the impact of RD on IO treatment response.

The role of cytoreductive nephrectomy and systemic therapy in the management of tumor thrombus in patients with metastatic renal cell carcinoma

345

Background: Patients (pts) with metastatic renal cell carcinoma (mRCC) and tumor thrombus have historically been treated with cytoreductive nephrectomy (CN), however, their outcomes remain poor. Recent phase III data suggest the role for cytoreductive nephrectomy (CN) in mRCC is limited. To date, only case-reports have described thrombus response to systemic therapy. Here, we describe response and survival outcomes of de novo mRCC patients with thrombi treated with systemic therapy with or without CN. Methods: Pts with de novo mRCC at the Princess Margaret Cancer Centre were identified. Demographics, disease characteristics (including the presence of thrombus) and survival outcomes were collected. Progression free survival (PFS) and overall survival (OS) in months (m) was calculated using the Kaplan-Meier method (log-rank). Results: We identified 226 pts with de novo mRCC between 2002 and 2019. Pt demographics are listed in the table. In total, 157 pts underwent a CN and 69 received only systemic therapy. Of the total cohort, 64 pts (28%) had tumor thrombus at presentation (46 CN, 18 no CN). Of the 18 patients with tumor thrombus treated with only systemic therapy, 17 received first-line angiogenesis inhibitors and 1 had chemotherapy (medullary histology). Six (33%) had thrombus progression, 8 (44%) had stable disease and four (22%) had an objective response. Median PFS and OS for patients with and without tumor thrombus treated with systemic therapy only was not significantly different [5.3m (95% CI 3.6-11.7) vs 4.1m (95% CI 3.1-5.9)), p=0.33; OS: 12.1m (95% CI 8.8-27.7) vs 13.9m (95% CI 7.9-21.5), p=0.87). PFS for patients with tumor thrombus who had CN was similar to those treated with systemic therapy alone [8.4m (95% CI: 5.7-13.4) vs 5.3m (95% CI 3.6-11.7), p=0.57] but OS was significantly better favoring CN [29.4m (95% CI: 17.4-48.9) vs 12.1m (95% CI 8.8-27.7), p=0.01). Conclusions: In this largest series of patients with mRCC and thrombus treated with systemic therapy +/- CN, CN appears to plays an important role. More data is needed for patients with tumor thrombus treated with immunotherapy to confirm these findings and elucidate the role of surgery in those cohorts. Bias due to the retrospective study design is an important limitation.[Table: see text]

The impact of multimodality therapies in marginally inoperable soft tissue sarcomas (STS): The Toronto Sarcoma Program (TSP) experience

11548

Background: The mainstay therapy of operable STS remains surgery, which may include (neo)adjuvant therapies. Within the TSP, marginally inoperable STS are often treated with sequential chemo (CTX) and radiation (RT) therapy, followed by surgery (SX). Herein we present our experience of multi-modality therapies for marginally inoperable STS patients (pts). Methods: This was a dual-center, single program, retrospective review. Pts were included if deemed to have marginally inoperable primary or recurrent STS, as determined at the TSP tumor board. Pts included must have had CTX with the intent of having RT and SX after. Pts demographics, treatment details and clinical outcomes data were collected. Relapse free survival (RFS) and overall survival (OS) were estimated using the Kaplan-Meier method. Multivariate analysis of the influence of disease characteristics and treatment on outcomes was assessed using Cox regression. Results: From June 2005 to May 2019, 75 pts were identified. Median age was 52 years (range 16-72). Pts were predominantly male (55%). Histological subtypes included dedifferentiated liposarcoma (29%), leiomyosarcoma (27%), synovial sarcoma (19%) and others (25%). Primary tumor was located in the retroperitoneum (48%), extremity (23%), pelvis (12%), thorax (9%), and other sites (8%). All pts had doxorubicin and ifosfamide CTX (median 4 cycles; range 1-6), while RT dose delivered was 50.4Gy/28 fractions in 58 (77%) of cases. Twenty three pts (31%) achieved partial response, 40 pts (53%) had stable disease and 12 pts (16%) had progression of disease (PD) on CTX, of which half (8%) did not undergo further treatment. Nine pts (12%) underwent CTX followed by SX due to significant response, 9 pts (12%) underwent CTX and RT without SX due to persistent tumor unresectability or PD. The final 50 pts (67%) completed multi-modality treatment (CTX, RT & SX). Overall, 59 pts (79%) had SX; negative margins were achieved in 53 (71%). 19 pts (25%) had postoperative complications, causing death in 2 pts (2.7%). With a median follow-up of 72 months, median RFS and OS were 26.9 months (95% CI: 0-86.0), and 65 months (95% CI: 13.5-116.4). Extremity location was associated with superior RFS (median not reached [NR], HR 0.28 95% CI 0.09-0.83, p = 0.022), and OS (median NR, HR 0.29 95% CI 0.09-0.90, p = 0.032). Receipt of RT was associated with superior RFS (median NR, HR 0.23 95% CI 0.10-0.52, p < 0.001); and OS (median NR, HR 0.21 95% CI 0.09-0.50, p < 0.001). Pts who had PD after CTX were associated with poor outcomes - RFS (median 4.7 months, HR 2.03 95% CI 0.61-6.76, p = 0.24); and OS (median 21.9 months, HR 2.48 95% CI 0.73-8.47, P = 0.144). Conclusions: Multi-modality approach resulted in successful resection for most pts with marginally inoperable STS. Extremity location and RT administration were associated with better RFS and OS, while progression on CTX confers worse survival outcomes.

A phase II, open-label, randomized trial of durvalumab (D) with olaparib (O) or cediranib (C) in patients (pts) with leiomyosarcoma (LMS)

11522

Background: The use of immune checkpoint blockade (ICB) in non-inflamed (cold) tumors is associated with limited clinical efficacy. Combination of ICB with certain molecularly targeted agents (MTA) is hypothesized to increase tumor immunogenicity by recruiting tumor infiltrating lymphocytes in cold tumors, such as LMS. Here, we present the results of LMS cohort treated on the DAPPER study (NCT03851614). Methods: LMS pts with ECOG 0-1 were randomized to either D+O (arm A), or D+C (arm B). In a 28-day cycle, D 1500mg i.v. q4w with either O 300mg bid po qd or C 20mg po qd 5d/week were administered. Overall response rates (ORR) were determined using RECISTv1.1. Evaluation of tumor kinetics (TK) was performed by calculating tumor growth rate (TGR) of target lesions on CT images at baseline and on-treatment, adjusted to account for the time difference between scans. TGR is expressed as % tumor growth/week (Ferte C et al. CCR, 2014). Additionally, paired FFPE samples (from baseline and on-treatment biopsies) were assessed using multispectral fluorescent immunohistochemistry (IHC) panel: CD3, CD8, CD20, CD68, FOXP3 and cytokeratin. Tumor areas were identified by a pathologist and immune cells were quantified using InForm image analysis software. Results: 25 metastatic LMS pts were randomized to arm A (n = 11) or B (n = 14) over 21 months. Median age was 53 years, 96% were females and 60% of pts had ≥3 lines of therapy. In 23 evaluable pts, no responses were seen, 7 pts had stable disease (SD) while 16 has progressive disease (PD). TK analysis was evaluable for 18 pts (arm A = 8, B = 10). 5/8 pts (62.5%) in arm A and 6/10 pts (60%) in arm B showed decreased TK (defined as TGRbaseline > TGRon-treatment). In 4/5 (80%) pts who had deceleration of TK in arm A, SD was maintained for ≥6 months. The reduction in TGR on treatment, compared to baseline was significant in arm A but not in arm B (measured as median % tumor growth/week of 0.5 vs 5.1, 95% CI 0.2-4.3, p = 0.035 in arm A; and 1.3 vs 2.9, 95% CI 0.2-2.7, p = 0.088 in arm B). The median PFS of arm A and B were 9 (95% CI 3-12.8) and 4 (95% CI 2.2-4.6) months respectively. There were no statistically significant differences in tumor-infiltrating immune cells when comparing baseline and on-treatment biopsies from arm A or B. In arm A, one pt with SD > 6 months had a 2.5-fold increase in CD8 (CD3+CD8+) T cells and a 7.6-fold increase in macrophages (CD68+). Conclusions: D+O or D+C resulted in stable disease in 30% of pts, mostly on arm A (D+O). TK analysis may identify pts with prolonged SD on treatment. Although a cold-to-hot immunophenotype change was not generally seen, changes in tumor infiltrating immune cell subsets were observed in one patient with prolonged stable disease. These findings support further molecular and immunophenotype characterization in LMS patients treated with D+O or D+C. Clinical trial information: NCT03851614.

UnCHAARTED territory: The role of docetaxel rechallenge following chemohormonal therapy for metastatic castrate-sensitive prostate cancer

117

Background: Since docetaxel has been advanced to the metastatic castrate-sensitive prostate cancer (mCSPC) setting, there is a lack of evidence guiding its re-introduction upon castrate-resistant (CR) progression. We sought to identify clinical characteristics and outcomes of patients subjected to docetaxel rechallenge (DR) following prior docetaxel exposure in the mCSPC realm. Methods: Patients rechallenged with docetaxel following treatment in the mCSPC setting were identified from three academic centres in Ontario, Canada. Retrospective chart reviews were performed to identify clinical, treatment and outcome variables. Results: Of the 45 patients with DR initiated between 06/2015 and 07/2020, the median age was 65, 60% had a Gleason score of ≥8, and 64% had an ECOG of ≤1. 56% had bone only metastasis, 4% lymph node only metastasis, 29% bone and lymph node metastasis, and 11% had visceral metastasis. In the mCSPC setting, 98% of patients received 6 cycles of docetaxel with 13% requiring dose delays. Of 43 informative patients, all had a PSA response to chemohormonal therapy. 91% achieved at least a 50% PSA response (PSA50), of which 40% had a 50-89% PSA reduction and 51% had a ≥90% PSA reduction. 29% of patients obtained a PSA nadir of < 0.2 ng/mL. 16% had CR progression in < 6 months, 56% in 6-12 months, and 28% in > 12 months. DR was initiated after a median of 20.8 months (range 6.0-40.4) following the last dose of docetaxel for mCSPC, and was given as first line treatment for CR disease to 7%, second line to 51%, third line to 40%, and fourth line or beyond to 2% of patients. 69% of patients had received an androgen-receptor axis targeted therapy prior to DR, 18% radium 223, and 7% had received a trial drug. Notably, no patients had received cabazitaxel prior to DR. The median number of cycles of docetaxel received at rechallenge was 5 (range 1-11) with 18% of patients requiring treatment delays. 64% of patients stopped treatment due to progression, 16% due to side effects, 7% at the patient’s request, 7% due to completion of the planned number of cycles, and 6% due to death or other causes. Among 44 informative patients, 23% achieved at least a PSA50, with 18% having a 50-90% PSA reduction, and 5% having a ≥90% PSA reduction. The median time to progression (biochemical, radiographic, or death) was 2.3 months (95%CI 1.7-4.4) and the median overall survival was 11.0 months (95%CI 8.5-14.3). Conclusions: DR following exposure to docetaxel in the mCSPC setting resulted in a PSA50 in only around one quarter of patients. Both the median time to progression and overall survival were found to be short. With future investigations, we hope to identify clinical variables that will help predict which patients might benefit most from DR.

Prognostic factors that affect survival outcomes in men with metastatic castration-resistant prostate cancer (mCRPC) treated with radium-223

225

Background: Radium-223 (Ra-223) improved overall survival (OS) in men with mCRPC with predominantly bone metastases. We analyzed their survival outcomes to identify factors associated with prognosis for men treated with Ra-223. Methods: This was a retrospective study of men with mCRPC at Princess Margaret Cancer Centre treated with Ra-223. Demographics, disease characteristics, number of bone metastasis [ < 6, 6-20, > 20], laboratory results, number of Ra-223 doses, systemic treatment lines after radium-223, use of bone protecting agents (BPA) and survival outcomes were collected. OS and progression-free survival (PFS) were estimated by Kaplan-Meier (log-rank) analysis. Uni- (UVA) and multi-variate (MVA) analysis (Cox-regression) were used to evaluate patient and disease characteristics, number of Ra-223 doses and overall survival. Results: 114 men received Ra-223 between May 2015 and May 2018 with median age 75 years (range 53-93). Median radium doses was 5 (68 [59.6%] received > 4 doses, 46 [40.4%] received ≤4 doses). Median baseline ALP 113.5 U/L (31-1121), median baseline Hb 118 g/L (69-153), median baseline PSA 70.2 ug/L (0.15-5275), median LDH 242 UL (82-1426). 58% had 6-20 bone metastases and 28% had > 20 bone metastases. The median OS and PFS for men who received ≤4 doses vs > 4 doses was 4.56 vs 19.8 months (HR = 8.4; 95%CI: 4.861-14.62; p≤ 0.0001) and 2.9 vs 7.45 months (HR = 4.6; 95%CI: 2.837 to 7.537; p≤ 0.0001) respectively. The baseline median ALP was (154 vs 98; p = 0.03) for men who received ≤4 doses vs > 4 doses Ra-223. On UVA, ECOG 0-1 (HR = 0.33; p = 0.0003), baseline PSA < 70 ug/L (HR = 0.51; p = 0.0023), LDH < 250 U/L (HR 0.55; p = 0.0082), Hb > 120 g/L(HR 0.46; p = 0.0004), ALP < 150 U/l(HR 0.38; p ≤ 0.0001) and receipt of subsequent treatment after Ra-223 (HR = 0.33; p < 0.0001) were associated with improved OS. On MVA, receipt of subsequent treatment, administration > 4 cycles of Ra-223 and baseline ALP < 150 U/L were associated with improved OS. Conclusions: Men who receive > 4 cycles of Ra-223 have significantly better OS than those who receive ≤4 doses. Baseline ALP was independently associated with better OS and could be used to identify patients most likely to benefit from Ra-223.

Clinical characteristics of nonosteogenic, non-Ewing’s sarcoma of the bone: Experience at the Toronto Sarcoma Program

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Background: Non-osteogenic sarcoma of the bone is a rare entity comprising a heterogenous group of malignant tumors. Clinical characteristics and outcome data are sparse in the literature. We evaluated the characteristics and long-term outcomes of patients (pts) with this disease. Methods: Pts with non-osteogenic sarcoma of the bone treated at the Toronto Sarcoma Program from 1987-2017 were identified from our institutional sarcoma database. Patient characteristics (ie: age, gender, tumor size, histology, grade, necrosis, tumor location), treatment modality (ie: surgical management, chemotherapy, radiotherapy), and survival information were collected. Survival was estimated by Kaplan-Meier (log-rank). Multi-variate analysis (MVA) was used to evaluate characteristics for sarcoma specific survival. Results: Of 130 pts identified, 106 had non-metastatic disease with a median age of 46 (range 18-89). Male-to-female predominance was 1.5:1. Common histologies were undifferentiated pleomorphic sarcoma (UPS; 42%), leiomyosarcoma (21%), and fibrosarcoma (11%). Tumors were generally high grade (59%) and > 5 cm in size (73%). The majority of pts received chemotherapy (68%), with Cisplatin/Doxorubicin based regimens (95%). R0 resection was achieved in 85% of cases. Survival for the entire cohort, showed a median (m)DFS of 8.13 years (95%CI:2.52-18.02), and a mOS of 11.72 (95%CI:7.00-not reached [NR]). Median sarcoma specific survival was NR, however 15- and 25-year survivals were 60.4% and 52.6% respectively. MVA demonstrated axial tumor location (HR = 13.03; p = 0.005), no chemotherapy (HR = 4.50; p = 0.017) and tumor grade (G2: HR = 36.21; p = 0.012; G3: HR = 20.30; p = 0.015) as risk factors for sarcoma specific death. Tumor size > 10cm (p = 0.085) and necrosis > 90% (p = 0.082) trended towards significance. Conclusions: Non-osteogenic sarcoma of the bone is a rare tumor entity, with a predominant UPS histology. Patient outcomes are reasonable, with measurable long-term survival. Axial tumor location, absence of chemotherapy, and high-grade disease predict for worse survival outcome. Further evaluation with larger data series is warranted to more fully understand this disease.

Phase 1b study of selinexor, a first-in-class selective inhibitor of nuclear export (SINE) compound, in combination with doxorubicin in patients (pts) with locally advanced or metastatic soft tissue sarcoma (STS)

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Background: Selinexor is a first-in-class SINE compound with single-agent activity in STS. We undertook this study to determine the safety, tolerability and efficacy of selinexor in combination with doxorubicin in pts with incurable STS. Methods: This phase 1b study was conducted using a bayesian model (modified toxicity probability index). Patients with locally advanced or metastatic STS received selinexor at either 60 or 80mg weekly PO plus doxorubicin (75mg/m2 IV q21 days, max 6 cycles). Pts with stable disease (SD) or better (per RECIST 1.1 criteria) after 6 cycles of combination treatment received selinexor monotherapy until disease progression or unacceptable toxicity. Disease assessments were made with standard imaging after every 2 cycles. Results: 24 pts (19F/5M, ECOG 0/1: 12/12, median age 58.5 years [range 34-74]) were enrolled. Disease subtypes included leiomyosarcoma (n = 6), malignant peripheral nerve sheath tumor (n = 3) and other sarcomas (n = 15). Three pts at 60mg selinexor and 21 pts at 80mg selinexor were treated. The most common G3 drug related adverse events were hematological, neutropenia n = 13 (54%), anemia n = 6 (25%). There were 4 dose-limiting toxicities (2 febrile neutropenia, 1 vomiting and 1 unresolved fatigue) all at the 80mg dose level, but does not satisfy criteria for maximum tolerated dose. Two patients had clinically significant and relevant drop in ejection fraction, presenting with cardiac symptoms. Of the 24 evaluable pts 4 (17%) had a partial response, 16 (67%) had SD as best response and SD > 16 weeks was seen in 13 pts (54%). PK analysis of selinexor did not demonstrate changes compared to single agent profile. The estimated median PFS and OS are 5.5 (95% CI:4.1-7.0) and 9.4 (6.6-13.8) months. Conclusions: Our initial data demonstrate that the combination of selinexor at 80mg with doxorubicin is tolerable and is associated with clinical benefit. Longer term follow up of available patients will be needed to understand toxicity profile. Clinical trial information: NCT03042819.

Cross-trial comparison of taxane versus non-taxane combination chemotherapy regimens for advanced penile cancer (APC): A systematic review

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Background: Penile cancer is rare and there are scant data on the optimal chemotherapy regimen. The majority of trials are single arm, non-randomized studies. Here we report on a systematic review aiming to compare taxane combination chemotherapy regimens with non-taxane regimens for APC. Methods: A systematic review was conducted in accordance with the PRISMA guidelines. Medline, Embase and Cochrane Central Register of Controlled Trials databases were searched using the following terms: penile cancer, penis, antineoplastic combined chemotherapy, taxane, docetaxel, paclitaxel, platinum, cisplatin, carboplatin. Studies were identified using preplanned eligibility criteria by 2 investigators (EA-E and JR). Data were extracted independently by EA-E and JR. Studies were weighted by study sample size and those comparing taxane-based chemotherapy were compared to non-taxane therapy using the Mann Whitney test. Results: The search identified 1929 publications and 40 were selected for further assessment. Of these, 8 met eligibility criteria (7 prospective and 1 retrospective). Three studies tested taxane combinations (docetaxel, cisplatin and 5FU [DCF] and paclitaxel, ifosfamide and cisplatin [TIP]). A total of 148 men with APC were treated with non-taxane regimens and 98 men received a taxane combination. Patient characteristics (age, ECOG status, stage, number of cycles) were comparable between the two groups. Partial response and overall response rates were significantly higher in the taxane versus the non-taxane group (35.7% vs. 24.2% p = 0.01 and 41.9% vs. 32.5% p = 0.007) respectively. Grade3/4 neutropenia was significantly higher in taxane group than non-taxane group (27.8% vs 19.4% p = 0.02). Median PFS and OS was numerically but not significantly higher in the taxane versus the non-taxane group (5.7 vs. 4.4 months, p = 0.45 and 12.1 vs 10 months, p = 0.48, respectively). Conclusions: Compared to non-taxane-based regimens, taxane combinations have higher response rates and may improve survival in APC. Hematologic toxicities are worse with taxane containing regimens. Taxane combinations should be the preferred regimen for suitable men with APC.