Sasanlimab in combination with bacillus Calmette-Guérin (BCG) in BCG-naive, high-risk non–muscle-invasive bladder cancer (NMIBC): Event-free survival (EFS) subgroup analyses based on disease stage from the CREST study.

4517 Background: Sasanlimab in combination with BCG (induction [IND] and maintenance [MNT]) significantly improved investigator (INV)-assessed EFS vs BCG (IND and MNT) and had a manageable safety profile in patients (pts) with BCG-naive, high-risk NMIBC, according to the primary analysis results from the phase 3 CREST study. Here, we report exploratory EFS subgroup analyses not previously presented based on disease stage at randomization from Arms A and C. Methods: Eligible pts were randomized 1:1:1 to receive sasanlimab in combination with BCG (IND and MNT; Arm A), sasanlimab in combination with BCG (IND; Arm B), or BCG (IND and MNT; Arm C). To assess the impact on efficacy of carcinoma in situ (CIS) and T1 tumors at baseline, post hoc INV-assessed EFS analyses were conducted for the comparison of Arm A vs Arm C. EFS was defined as time from randomization to recurrence of high-grade disease, progression of disease, persistence of CIS (for patients with CIS at randomization), or death due to any cause, whichever occurred first. Results: At the data cutoff date (Dec 02, 2024), the median duration of follow-up for EFS was 36.4 and 36.7 months for Arm A and Arm C, respectively. A total of 176 pts with CIS (with or without papillary tumors) were in Arms A and C, 102 of whom had CIS without papillary tumors. A total of 398 pts with T1 tumor were in Arms A and C, 342 of whom had T1 tumor without CIS (Table). Three-year landmark EFS subgroup analyses not previously presented are reported in the table. For patients with CIS, with or without concomitant papillary tumors, the 3-year EFS rate was 83.0% in Arm A and 71.8% in Arm C. For patients with T1 tumors, with or without CIS, the 3-year EFS rate was 81.3% in Arm A and 72.2% in Arm C. Conclusions: Sasanlimab in combination with BCG (IND and MNT) improved EFS outcomes in the overall population and in the subgroups of pts with BCG-naive, high-risk NMIBC who had CIS or T1 tumors at randomization. This post hoc analysis further supports the potential of sasanlimab in combination with BCG as a practice-changing treatment in pts with aggressive disease. Clinical trial information: NCT04165317 . Arm A(N=352) Arm C(N=351) HR (95% CI) Arm A vs Arm C n (%) 36-mo EFS rate, % (95% CI) n (%) 36-mo EFS rate, % (95% CI) All pts 82.1 (77.4-85.9) 74.8 (69.7, 79.2) 0.68 (0.489-0.941) a Tumor type at randomization CIS with and without papillary tumors 88(25.0) 83.0 (72.9-89.6) 88(25.1) 71.8 (60.4-80.5) 0.53(0.285-0.982) CIS without papillary tumors 52(14.8) 81.0 (66.6-89.7) 50(14.2) 75.4 (59.9-85.6) 0.52 (0.233-1.165) T1 with and without CIS 204(58.0) 81.3 (74.7-86.4) 194(55.3) 72.2 (65.0-78.2) 0.63 (0.406-0.963) T1 without CIS 178 (50.6) 79.6 (72.1-85.2) 164(46.7) 72.5 (64.6-78.9) 0.70 (0.446-1.109) a Stratified HR; all other HR unstratified.