Results from BLASST-1 (Bladder Cancer Signal Seeking Trial) of nivolumab, gemcitabine, and cisplatin in muscle invasive bladder cancer (MIBC) undergoing cystectomy.

Abstract

439 Background: Cisplatin-based neoadjuvant chemotherapy (NAC) in MIBC improves survival which correlates with pathologic response (PaR) at radical cystectomy (RC). The combination of immunotherapy and NAC may improve PaR and outcomes in MIBC. We tested the efficacy and safety of nivolumab (N) with gemcitabine-cisplatin (GC) as neoadjuvant therapy for MIBC in our phase II trial (NCT03294304). Methods: Eligible pts with MIBC (cT2-T4a, N≤1, M0) who were candidates for RC were enrolled. Pts received C (70mg/m2) IV on D1, G (1000mg/m2) on D1,D8 and N (360 mg) IV on D8 every 21 days for 4 cycles followed by RC within 8 weeks. The primary endpoint was PaR (≤pT1,N0). Secondary objectives were safety of GC+N and PFS at 2 years. The correlative objectives based on pre-treatment biopsies were correlation of PaR with 1) WGS 2) molecular subtypes of BC; 3) PD-L1 expression; 4) baseline TILs, CD3, CD8 and CD56.. Evaluable pts. should have received at least 1 dose of N. PaR will be summarized by the PaR rate as estimated by the sample proportion with exact 95% confidence intervals. We specified a null PaR of 0.35 and an alternative hypothesis of 0.55; we will reject the null hypothesis if at least 20 of 41 pts. have a PaR. Results: Between Feb 2018 and June 2019, 41 pts. were enrolled (cT2N0 90%, cT3N0 7%, cT4N1 3%); 2 patients refused surgery but were included in ITT population. PaR was observed in 27/41 pts. (65.8%), including pts with N1 disease. The combination was safe with manageable toxicities and no deaths from treatment. Majority of AEs were from GC; the overall rates of grade 3-4 AEs was 20%, majority being neutropenia, thrombocytopenia and renal insufficiency. Immune related AEs were seen in 3 patients, 2 had "adenitis" which wasymptomatic,1 pt developed Guillian Barre Syndrome after surgery, which resolved with IVIG; and none of them required steroids. There was no delay in time to RC and no unexpected surgical complications from treatment. Patients are being followed for progression and survival. Correlative work is ongoing. Conclusions: Neoadjuvant N+GC is safe and effective in MIBC with significant pathologic downstaging rates and no added toxicities or delay to surgery. Clinical trial information: NCT03294304.