PD36-07: Defining optimal candidates for bladder-sparing treatment in muscle-invasive bladder cancer: analysis using pathological reference standards after chemoradiation
Associate Professor Tokyo Medical and Dental University
Introduction: Bladder-sparing treatment based on chemoradiotherapy (CRT) has taken a large interest as an alternative to radical cystectomy (RC) for muscle-invasive bladder cancer (MIBC). However, major concerns include MIBC recurrence even after achieving clinical complete response (CR) to CRT, which may be derived from microscopic cancer remnant in the preserved bladder. We have conducted a bladder-sparing protocol that incorporates induction CRT and subsequent partial cystectomy (PC). In addition, CRT was administered as an induction therapy before RC for MIBC patients who had no indication for bladder preservation. In this study, we analyzed these patient series and investigated clinical determinants of CRT response using the pathological reference standards to define optimal candidates for bladder preservation. Methods: We analyzed 285 patients with cT2-4N0M0 bladder cancer who underwent CRT (40 Gy to the true pelvis with concurrent cisplatin) followed by PC/RC (approval # M2019-192). CRT response was assessed using the cystectomy specimens. Risk factors related to the CRT response were identified using multivariable logistic regression model, and the accuracy of the multivariable model was assessed using the area under the curve (AUC) in the receiver operating characteristic curve (ROC) analysis. Results: Clinical T stage was T2/3/4 in 169 (59%)/105 (37%)/11 (3.9%) patients, respectively. The median tumor size was 3.0 cm and 108 patients (38%) had multiple tumors. Hydronephrosis was observed in 69 patients (24%). Overall, 54 (19%), 34 (12%), and 60 (21%) patients had bladder neck involvement (BNI), concomitant carcinoma in situ, and variant histology in the transurethral resection before CRT. The cystectomy specimens revealed ypT0, defined as pathological CR (pCR), in 178 patients (63%). In the multivariable logistic regression analysis, cT3-4 (Odds ratio=0.53 [95% confidence interval: 0.30-0.92]), tumor size>3.0 cm (0.45 [0.26-0.80]), multiplicity (0.34 [0.19-0.59]), and BNI (0.40 [0.20-0.80]) were independently associated with pCR. The final model including the four factors yielded the AUC of 0.75. In the cohort, 85 (30%), 83 (29%), and 117 (41%) patients had 0, 1, and 2 or more risk factors, respectively; pCR rates after CRT in the respective groups were 87%, 65%, and 43% (p < 0.001). Conclusions: Our analysis identified independent risk factors related to CRT response using the pathological reference standards, which may help decide the indication of bladder preservation in MIBC patients. SOURCE OF Funding: None
