Abstract
METHODS
We performed an international, multicentre, retrospective study to investigate the efficacy of anti-PD-(L)1 monotherapy in dMMR mCRPC. dMMR was defined as MMR protein loss on immunohistochemistry (IHC), and/or a deleterious alteration in an MMR gene or MSI-H status according to polymerase chain reaction analysis or next-generation sequencing. The primary endpoint was progression-free survival (PFS).
CONCLUSIONS AND CLINICAL IMPLICATIONS
These data confirm the efficacy of anti-PD-(L)1 therapy in patients with dMMR mCRPC and warrant consideration of reimbursement for anti-PD-(L)1 agents in dMMR mCRPC by health authorities.
BACKGROUND AND OBJECTIVE
Up to 5% of patients with metastatic castration-resistant prostate cancer (mCRPC) harbour loss-of-function alterations in mismatch repair genes (dMMR) resulting in microsatellite instability (MSI-H). Data on the efficacy of immune checkpoint inhibitors (ICIs) in dMMR mCRPC are limited, and reimbursement for these agents is not universally available.
KEY FINDINGS AND LIMITATIONS
Between July 2016 and July 2024, 93 patients with a median age of 70 yr (range 46-90) started anti-PD-(L)1 treatment. Patients were classified as dMMR on the basis of IHC results (n = 37, 40%), genomic alterations in MMR genes (n = 55, 59%), and/or an MSI-H phenotype (n = 64, 69%). Among evaluable patients according to Response Evaluation Criteria in Solid Tumours v1.1, the objective response rate was 46% (n = 84; 95% confidence interval [CI] 35-58%). A prostate-specific antigen decline ≥50% was observed in 60% of evaluable patients (n = 68; 95% CI 48-72%). Median PFS across the entire cohort was 7.7 mo (95% CI 5.3-12.4), with 1-yr, 2-yr, and 3-yr PFS rates of 39%, 27%, and 26%, respectively. Median overall survival was 27.0 mo (95% CI 17.7-43.5). PFS was significantly longer for patients with positive dMMR status on two or more tests than for patients with just one positive dMMR test.