Identification of Hypermutation and Defective Mismatch Repair in ctDNA from Metastatic Prostate Cancer.

PURPOSE: DNA mismatch repair defects (MMRd) and tumor hypermutation are rare and under-characterized in metastatic prostate cancer (mPC). Furthermore, because hypermutated MMRd prostate cancers can respond to immune checkpoint inhibitors, there is an urgent need for practical detection tools. EXPERIMENTAL DESIGN: We analyzed plasma cell-free DNA-targeted sequencing data from 433 patients with mPC with circulating tumor DNA (ctDNA) purity ≥2%. Samples with somatic hypermutation were subjected to 185 × whole-exome sequencing and capture of mismatch repair gene introns. Archival tissue was analyzed with targeted sequencing and IHC. RESULTS: Sixteen patients (3.7%) had somatic hypermutation with MMRd etiology, evidenced by deleterious alterations in MSH2, MSH6, or MLH1, microsatellite instability, and characteristic trinucleotide signatures. ctDNA was concordant with mismatch repair protein IHC and DNA sequencing of tumor tissue. Tumor suppressors such as PTEN, RB1, and TP53 were inactivated by mutation rather than copy-number loss. Hotspot mutations in oncogenes such as AKT1, PIK3CA, and CTNNB1 were common, and the androgen receptor (AR)-ligand binding domain was mutated in 9 of 16 patients. We observed high intrapatient clonal diversity, evidenced by subclonal driver mutations and shifts in mutation allele frequency over time. Patients with hypermutation and MMRd etiology in ctDNA had a poor response to AR inhibition and inferior survival compared with a control cohort. CONCLUSIONS: Hypermutated MMRd mPC is associated with oncogene activation and subclonal diversity, which may contribute to a clinically aggressive disposition in selected patients. In patients with detectable ctDNA, cell-free DNA sequencing is a practical tool to prioritize this subtype for immunotherapy.See related commentary by Schweizer and Yu, p. 981.

Checkpoint inhibitors in patients with metastatic renal cell carcinoma: Results from the International Metastatic Renal Cell Carcinoma Database Consortium.

BACKGROUND: To the authors' knowledge, outcomes and prognostic tools have yet to be clearly defined in patients with metastatic renal cell carcinoma (mRCC) who are treated with immuno-oncology (IO) checkpoint inhibitors (programmed death-ligand 1 [PD-L1] inhibitors). In the current study, the authors aimed to establish IO efficacy benchmarks in patients with mRCC and update patient outcomes in each International Metastatic Renal Cell Carcinoma Database Consortium (IMDC) prognostic class. METHODS: A retrospective analysis was performed using the IMDC database with data from 38 centers. It included patients with mRCC who were treated with ≥1 line of IO. Overall response rates (ORRs), duration of treatment (DOT), and overall survival (OS) were calculated. Patients were stratified using IMDC prognostic factors. RESULTS: A total of 687 patients (90% with clear cell and 10% with non-clear cell) were included. The ORR was 27% in evaluable patients (461 patients). In patients treated with first-line nivolumab and ipilimumab (49 patients), the combination of PD-L1 inhibitor and vascular endothelial growth factor inhibitor (72 patients), and PD-L1 inhibitor (51 patients), the ORR was 31%, 39%, and 40%, respectively, and the median DOT was 8.3 months, 14.7 months, and 8.3 months, respectively. The ORR for second-line, third-line, and fourth-line nivolumab was 22%, 24%, and 26%, respectively. The median DOT was 5.7 months, 6.2 months, and 8.3 months, respectively, in the second-line, third-line, and fourth-line settings. When segregated into IMDC favorable-risk, intermediate-risk, and poor-risk groups, the median OS rates for the first-line, second-line, third-line, and fourth-line treatment settings were not reached (NR), NR, and NR, respectively (P = .163); NR, 26.7 months, and 7.4 months, respectively (P < 0. 0001); 36.1 months, 28.2 months, and 11.1 months, respectively (P = .016); and NR, NR, and 6.7 months, respectively (P = .047). CONCLUSIONS: The ORR was not found to deteriorate from the first-line to the fourth-line of IO therapy. In the second line through fourth line, the IMDC criteria appropriately stratified patients into favorable-risk, intermediate-risk, and poor-risk groups for OS.