Residual CIS after neoadjuvant chemotherapy and radical cystectomy for muscle invasive bladder cancer: Implications for neoadjuvant trials

Purpose: To better define surrogate endpoints for neoadjuvant chemotherapy (NAC) trials in patients with muscle-invasive bladder cancer. We compared survival in patients with carcinoma in-situ (CIS) only vs. complete response following NAC and radical cystectomy (RC). Materials and Methods: Patients with cT2-4N0M0 disease treated with NAC and RC between 2001 and 2018 were stratified by response: complete response (CR, pT0N0), partial response (PR, pTaN0, pT1N0+/-CIS), CIS-only (pTisN0), stable disease (SD, pT2N0), or progressive disease (PD, >pT2N0). Primary endpoints were overall survival (OS) and risk of recurrence in patients with CIS-only vs. CR. Multivariable Cox proportional hazards regression model was used for OS and a competing risks proportional hazards model was used for risk of recurrence. Results: Of 1,406 patients in our institution cohort, 340 patients met inclusion criteria. Kaplan-Meier mean estimates of OS for CR and CIS-only were 108.9 months (95% CI 89.7–127.9) and 125.8 months (95% CI 112.3–139.3), respectively (P = 0.13). Cox proportional hazards model found no difference in OS between patients with PR (HR 1.06, 95% CI 0.33–2.58, P = 0.897) or CIS-only (HR 0.422, 95% CI 0.15–1.18, P = 0.101) when compared to CR. The risk of recurrence was similar between patients with CIS-only (HR 0.73, 95% 0.29–1.84, P = 0.49) and PR (HR 1.32, 95% CI 0.54–3.29, P = 0.54) when compared to CR on competing risks analysis. Conclusions: Residual CIS-only after NAC and RC demonstrated similar survival outcomes when compared to patients with pathologic CR. Further study in large multi-institutional cohorts may further validate CIS-only as an additional surrogate endpoint after NAC and may inform future trials.