Preferred treatment regimens for rare genitourinary (GU) malignancies.

780 Background: Rare GU cancers offer a challenge in determining standard of care therapy. Often data is extrapolated from small patient series or other tumor types to help guide clinicians. There is a lack of prospective data to guide therapy. Methods: We conducted a five-question survey via the Alliance for Clinical Trials in Oncology cooperative group network to identify commonly used and preferred regimens for the treatment of metastatic rare GU malignancies, including bladder squamous cell carcinoma (SCC), bladder adenocarcinoma, small cell bladder carcinoma (SCBC), penile SCC, and sex cord stromal tumors. Each question included 1) number of patients the provider treated per year, and 2) preferred frontline metastatic regimen for the rare tumor (multiple choice options drawn from the literature and selected after a discussion with a panel of experts (Table)). Surveys were emailed to the GU malignancy Alliance members, including academic and NCI Community Oncology Research Program (NCORP) sites. Responses were pooled and analyzed. Results: Fifty-one survey responses were received. One outlier was removed from the analysis leaving 50 responses. Twenty-six sites (52%) were NCORP, 22 sites were academic (44%), 2 sites were other. For the bladder SCC patients, the average number seen per year was 3.6 (range 0-15), 36.7% chose gemcitabine/platinum, 32.7% chose carboplatin/paclitaxel/gemcitabine, and 16.3% chose ITP as their preferred frontline regimen. For the adenocarcinoma bladder patients, the average number seen per year was 2.7 (range 0-10), 47.9% chose FOLFOX/CAPOX, 20.8% chose Gem-FLP, 16.7% chose FOLFOX/CAPOX + Bevacizumab and 6.2% chose ITP. For the SCBC patients, the average number seen per year was 3.1 (range 0-10), 62% chose platinum/etoposide with an immune checkpoint inhibitor compared to 36% who chose platinum/etoposide alone. For the penile SCC patients, the average number seen per year was 2.5 (range 0-10), 71.4% chose TIP,16.3% chose cisplatin/5FU and 10.2% chose immune checkpoint inhibitor. For the sex cord stromal tumor patients, the average number seen per year was 0.9 (range 0-10), 66.0% reported never treated and 19.2% chose BEP. Conclusions: This survey provides information on the most used regimens to treat rare GU malignancies and highlights the need for prospective studies to determine the best frontline therapy. These results are being used to inform the design of a first-line clinical trial to evaluate the most efficacious therapy for these rare GU malignancies. Survey Choices Option 1 Option 2 Option 3 Option 4 Option 5 - write in Bladder SCC ITP CarboTaxolGem GemPlatinum ddMVAC Bladder Adenocarcinoma ITP FOLFOX FOLFOX+bev Gem-FLP SCBC EP EP + ICI IA-EP Penile SCC TIP Cis/5FU ICI Cetuximab Sex Cord Stromal Tumor BEP VIP Never treated ITP - ifosfamide, paclitaxel, and cisplatin; EP – etoposide/platinum; IA-EP – ifosfamide/Adriamycin-EP; Gem-FLP – gemcitabine, 5-FU, leucovorin, cisplatin.