Oncologic outcomes in patients with residual invasive upper tract urothelial carcinoma following neoadjuvant chemotherapy.

475 Background: Emerging evidence supports use of neoadjuvant chemotherapy (NAC) prior to radical nephroureterectomy (RNU) for appropriately selected patients with upper tract urothelial carcinoma (UTUC). However, oncologic outcomes have not been well characterized for patients with residual muscle-invasive disease after NAC. Methods: We used a multi-institutional cohort from 24 centers in the U.S., Europe, and Japan to retrospectively identify patients who underwent RNU for UTUC from 1985-2022 and had high-grade muscle-invasive disease. We stratified the cohort based on receipt of NAC (>ypT2 vs. >pT2). Exclusion criteria included receipt of adjuvant chemotherapy, concurrent cystectomy with RNU, and distant metastatic disease. Baseline characteristics were compared between groups. Kaplan-Meier survival analysis with log-rank test was used to compare differences in recurrence-free survival (RFS), overall survival (OS), and cancer-specific survival (CSS). Multivariable Cox regression and Fine-Gray competing risk regression were used to determine predictors of these outcomes. Results: A total of 1,233 patients were included, 62 of whom received NAC prior to RNU. A platinum-based regimen was used in 90% of NAC recipients, and the median number of cycles administered was 4 (IQR: 3-5). Median follow-up time among all patients was 22 months (IQR: 8-47 mo.). NAC recipients were more likely to have pathologic node positivity (35% vs. 13%) and less likely to have positive tumor margins (8% vs. 28%). On Kaplan-Meier analysis, NAC recipients with residual >ypT2 disease had poorer outcomes than those with >pT2 disease (2-year RFS [NAC vs. no NAC]: 52% vs. 80%, p<0.001; 2-year OS: 60% vs. 78%, p=0.003; 2-year CSS: 61% vs. 86%, p<0.001). Multivariable analyses also showed a statistically significant association between residual muscle-invasive disease after NAC and poorer RFS, OS, and CSS (Table). Conclusions: NAC recipients with >ypT2 disease at RNU after exhibit poorer outcomes than stage-matched chemotherapy naïve counterparts. This may reflect effects of occult micrometastatic disease or chemoresistant primary tumors in non-responders. Our data highlight the need to improve prospective identification of candidates most likely to respond to NAC prior to RNU for UTUC in order to maximize its therapeutic benefit. [Table: see text]