LAUSR

e16007 Background: PUC is uncommon and highly aggressive, with limited data on treatment patterns, outcomes and prognostic factors. We hypothesized that PUC is associated with clinical under-staging, poor outcomes and lack of chemotherapy (CT) response. Methods: We conducted a retrospective review of pts with UC and plasmacytoid component (PUC), seen in our institution (2000 - 2018). Demographic and clinicopathologic data, treatment modalities, pathologic complete/partial response (pCR, pPR) to neoadjuvant CT (NAC), and overall survival (OS) from diagnosis and surgery (Sx) were captured. T-test, chi-square, and Cox-regression were used to explore potential prognostic associations. OS was estimated with KM method. Results: We identified 63 consecutive pts (51 men) with available data for analysis. Median age at diagnosis was 67 (44-89). During initial diagnostic workup, 32 (51%) pts had extravesical disease (cT3:24, cT4:8) and 23 (36.5%) hydronephrosis at imaging. Overall, 39 (62%) pts underwent Sx with curative intent, 25 (39.6%) were pre-treated with cisplatin-based NAC; adjuvant CT was given to 15 (24%). The remaining pts pursued bladder-sparing and/or palliative approaches. At time of Sx, 17/39 (43.6%) pts had pathologic upstaging, 10 (25.6%) had positive margins and 19 (48.7%) pN+ stage. In the NAC pt subset (25 pts), 5 (20%) had progression on scans, 19 (76%) had Sx; 2 pts had pCR (10.5%), 1 had pPR, 6 (31.5%) had pathologic upstaging. In the entire cohort, median follow-up was 8 months. Median OS was 20.7 months from diagnosis and 23.6 months from Sx. NAC was not significantly associated with longer OS (from Sx) (HR 1.53, 95%CI 0.16-15, p = 0.715) and the same was true for adjuvant CT (HR 0.64, 95%CI 0.1-4, p = 0.630). 15/39 pts recurred after Sx (38.4%), with 9/15 (60%) having peritoneal/retroperitoneal involvement. Conclusions: PUC frequently presented with advanced stage at diagnosis and demonstrated poor NAC response, frequent upstaging, positive margins and pN+ stage at Sx. More than half of patients who recurred after Sx, presented with (retro)peritoneal disease. Studies evaluating molecular biomarkers and drivers in PUC, and prospective clinical trials are being pursued.