DR-382 An international multicenter retrospective study on the efficacy of anti-PD-(L)1 monotherapy in microsatellite unstable castrate-resistant prostate cancer

Metastatic castrate-resistant prostate cancer (mCRPC) is generally insensitive to immune checkpoint inhibitor therapy (ICIs), partly due to its relatively low tumor mutation burden. Up to 5% of patients with mCRPC show a microsatellite unstable (MSI-H), hypermutated phenotype that is more sensitive to ICIs. While studies have demonstrated the clinical efficacy of ICIs among patients with MSI-H solid tumors, data on the efficacy of ICIs in mCRPC specifically is limited to small cohort studies with limited follow up data. The efficacy of ICIs may differ between tumor types due to differences in underlying tumor biology.  In this retrospective multicenter study, we aim to improve our insight into the efficacy of anti-PD-(L)1 ICI therapy in MSI-H mCRPC by combining data from the DRUP trial with data from other centres in and outside of Europe.

Niven Mehra, Radboudumc, the Netherlands