Pembrolizumab (pembro) for patients (pts) with high-risk (HR) non–muscle invasive bladder cancer (NMIBC) unresponsive to Bacillus Calmette-Guérin (BCG): Updated follow-up from KEYNOTE-057.

Abstract

4530 Background: Upregulation of the PD-1 pathway has been observed in BCG-unresponsive NMIBC, suggesting that pembro may be beneficial. Efficacy and safety of pembro in pts with HR, BCG-unresponsive NMIBC was evaluated in the single-arm phase 2 KEYNOTE-057 study (NCT02625961); updated results for pts with carcinoma in situ (CIS) with or without papillary tumors (cohort A) are reported. Methods: Pts with histologically confirmed HR, BCG-unresponsive CIS with or without papillary tumors who received adequate BCG therapy and were unable/refused to undergo radical cystectomy received pembro 200 mg Q3W for 24 mo or until recurrence, progression, or unacceptable toxicity. Pts who developed HR NMIBC or progressive disease during treatment were required to discontinue. Key end points were complete response rate (CRR), duration of response, and safety. Results: 102 pts (median age, 73 years; CIS alone, 63.7%; median number of prior BCG instillations, 12) had enrolled in cohort A as of enrollment cutoff. Median (range) duration of follow-up was 15.8 mo (4.6-28.2) ; 3-mo CRR was 40.2% (95% CI, 30.6-50.4) by central assessment. Among 41 pts who had CR at 3 mo, median CR duration was 12.7 mo (range, 0+ to 20.5+ mo); 75.4% had a CR duration ≥ 6 mo; 52.6% had a CR duration ≥12 mo (Kaplan-Meier method); 24 pts (58.5%) maintained CR at last follow-up, and 15 (36.6%) experienced recurrent NMIBC after CR; at the time of analysis, none progressed to muscle-invasive or metastatic disease. CRR was 44.6% for pts with CIS alone (n = 65), 41.7% for CIS with T1 tumors (n = 12), and 28.0% for CIS with high-grade Ta tumors (n = 25). Treatment-related adverse events (AEs) occurred in 66 (64.7%) pts; most frequent (≥10%) were pruritus (10.8%), diarrhea (10.8%), and fatigue (9.8%). Grade 3/4 treatment-related AEs occurred in 13 (12.7%) pts. Immune-mediated AEs occurred in 19 (18.6%) pts. Conclusions: Pembro continued to show encouraging antitumor activity in pts with HR, BCG-unresponsive CIS with or without papillary tumors and a safety profile consistent with that of previous experience. Updated data using additional follow-up will be presented. Clinical trial information: NCT02625961.