Impact of histology and toxicities on outcomes of patients with muscle invasive bladder cancer receiving neoadjuvant chemotherapy.

540 Background: Cisplatin-based neoadjuvant chemotherapy (NAC) followed by radical cystectomy (RC) extends survival in muscle invasive bladder cancer (MIBC) patients (pts). Pathologic complete response (pCR) is associated with survival. We conducted a retrospective study to examine the prognostic impact of other variables including histologic subtype, location, multifocality, margins, size of tumor and toxicities. Methods: Pts who underwent RC at Dana-Farber for MIBC stage T2-T4N0-1 were studied. Data were collected for demographics, clinical and pathologic variables. Descriptive stats were reported, and Cox proportional hazards regression analyses were conducted to examine the association with recurrence-free survival (RFS) and overall survival (OS). Results: From 2002 to 2018, 150 patients were available. The median age was 66 (range 36-89) and 102 (68%) were male. MVAC/dose dense MVAC, GC and other non-standard regimens were given in 42 (28%), 85 (56.7%) and 23 (15.3%) pts, respectively. The 2-yr RFS was 63.6%, the 5-yr OS was 68.7% and pCR occurred in 38 pts (25.3%). Multivariable analysis identified pure urothelial carcinoma in the residual tumor and absence of pathologic response to be associated with poor RFS and OS. Positive margins were associated with poor RFS, while grade ≥3 toxicities were associated with poor OS. Conclusions: Pure urothelial carcinoma histology was associated with worse RFS and OS following RC after NAC for MIBC, suggesting molecular studies may be useful in these cases. The association of severe toxicities with poor OS suggests that optimal pt selection for NAC and early recognition of toxicities is important.[Table: see text]