Microsatellite Instability, Tumor Mutational Burden, and Response to Immune Checkpoint Blockade in Patients with Prostate Cancer.

PURPOSE: Patients with microsatellite instability high/mismatch repair deficient (MSI-H/dMMR) and high tumor mutational burden (TMB-H) prostate cancers are candidates for pembrolizumab. We define the genomic features, clinical course, and response to immune checkpoint blockade (ICB) in patients with MSI-H/dMMR and TMB-H prostate cancers without MSI (TMB-H/MSS). METHODS: We sequenced 3,244 tumors from 2,257 prostate cancer patients. MSI-H/dMMR prostate cancer was defined as MSIsensor score ≥10 or MSIsensor score ≥3 and <10 with a deleterious MMR alteration. TMB-H was defined as ≥10 mutations/megabase. PSA50 and RECIST responses were assigned. Overall survival (OS) and radiographic progression-free survival (rPFS) were compared using log rank test. RESULTS: 63 (2.8%) men had MSI-H/dMMR and 33 (1.5%) had TMB-H/MSS prostate cancers. Patients with MSI-H/dMMR and TMB-H/MSS tumors more commonly presented with grade group 5 and metastatic disease at diagnosis. MSI-H/dMMR tumors had higher TMB, indel and neoantigen burden compared with TMB-H/MSS. 27 patients with MSI-H/dMMR and 8 patients with TMB-H/MSS tumors received ICB, none of whom harbored POLE mutations. 45% of MSI-H/dMMR patients had a RECIST response and 65% had a PSA50 response. No TMB-H/MSS patient had a RECIST response and 50% had a PSA50 response. rPFS tended to be longer in MSI-H/dMMR patients than in TMB-H/MSS patients who received immunotherapy. Pronounced differences in genomics, TMB or MSIsensor score were not detected between MSI-H/dMMR responders and non-responders. CONCLUSIONS: MSI-H/dMMR prostate cancers have greater TMB, indel and neoantigen burden compared with TMB-H/MSS prostate cancers, and these differences may contribute to more profound and durable responses to ICB.

Natural History and Genomic Landscape of Chemotherapy-Resistant Muscle-Invasive Bladder Cancer.

PURPOSE: Patients with residual invasive bladder cancer after neoadjuvant chemotherapy (NAC) and radical cystectomy have a poor prognosis. Data on adjuvant therapy for these patients are conflicting. We sought to evaluate the natural history and genomic landscape of chemotherapy-resistant bladder cancer to inform patient management and clinical trials. METHODS: Data were collected on patients with clinically localized muscle-invasive urothelial bladder cancer treated with NAC and cystectomy at our institution between May 15, 2001, and August 15, 2019, and completed four cycles of gemcitabine and cisplatin NAC, excluding those treated with adjuvant therapies. Survival was estimated using the Kaplan-Meier method, and multivariable Cox proportional hazards models were used to identify predictors of recurrence-free survival (RFS). Genomic alterations were identified in targeted exome sequencing (Memorial Sloan Kettering Integrated Mutation Profiling of Actionable Cancer Targets) data from post-NAC specimens from a subset of patients. RESULTS: Lymphovascular invasion (LVI) was the strongest predictor of RFS (hazard ratio, 2.15 [95% CI, 1.37 to 3.39]) on multivariable analysis. Patients with ypT2N0 disease without LVI had a significantly prolonged RFS compared with those with LVI (70% RFS at 5 years). Lymph node yield did not affect RFS. Among patients with sequencing data (n = 101), chemotherapy-resistant tumors had fewer alterations in DNA damage response genes compared with tumors from a publicly available chemotherapy-naïve cohort (15% v 29%; P = .021). Alterations in CDKN2A/B were associated with shorter RFS. PIK3CA alterations were associated with LVI. Potentially actionable alterations were identified in more than 75% of tumors. CONCLUSION: Although chemotherapy-resistant bladder cancer generally portends a poor prognosis, patients with organ-confined disease without LVI may be candidates for close observation without adjuvant therapy. The genomic landscape of chemotherapy-resistant tumors is similar to chemotherapy-naïve tumors. Therapeutic opportunities exist for targeted therapies as adjuvant treatment in chemotherapy-resistant disease.

Response to 2 Induction Courses of Bacillus Calmette-Guèrin Therapy Among Patients With High-Risk Non-Muscle-Invasive Bladder Cancer: 5-year Follow-Up of a Phase 2 Clinical Trial.

Importance: With the ongoing bacillus Calmette-Guèrin (BCG) shortage, alternate therapeutic options for patients with high-risk non-muscle-invasive bladder cancer (NMIBC) are needed. Objective: To report the 5-year outcomes of a cohort from a prospective phase 2 trial of patients with high-risk NMIBC who underwent 12 instillations of induction BCG without maintenance. Design, Setting, and Participants: Between November 2015 and June 2018, patients at Memorial Sloan Kettering Cancer Center with primary or recurrent NMIBC (high-grade Ta, T1 tumors, with or without carcinoma in situ) were prospectively enrolled to receive 2 induction courses (12 intravesical instillations) of BCG without maintenance therapy. The analysis itself took place on July 28, 2023. Main Outcomes and Measures: Recurrence-free survival (RFS) and cancer-specific survival (CSS) was assessed by landmark analysis at 7.5 months. Recurrence was defined as pathologic high-grade disease. Results: Among 81 patients (65 men [84%] and 12 women [16%] with a median [IQR] age of 72 [64-77] years) who consented to participate in the study, 75 remained evaluable for long-term follow-up analysis. Twenty-one patients experienced high-grade recurrence, yielding a 5-year RFS rate of 69% (95% CI, 58%-81%), with a median (IQR) follow-up of 4.4 (3.8-5.3) years for patients without recurrence. Three patients died of bladder cancer, corresponding to a CSS rate of 97% (95% CI, 93%-100%) with a median (IQR) follow-up of 4.9 (4.2-5.7) years for survivors. Using 2 induction courses reduced the amount of BCG per patient from 27 vials to 12 vials. Conclusion and Relevance: Twelve induction instillations of BCG without maintenance for patients with high-risk NMIBC reduced the number of vials needed per patient while providing acceptable oncologic outcomes. Given the ongoing BCG shortage, this modified regimen may provide a suitable alternative in this setting.