TMB-High, MSI-High Castration-Resistant Prostate Cancer Treated With Pembrolizumab

Area of Science:

• Oncology
• Genomics
• Immunotherapy

Background:

• Prostate cancer treatment landscape, particularly for advanced stages, often involves sequential therapies.
• Microsatellite instability-high (MSI-high) and tumor mutation burden-high (TMB-high) are predictive biomarkers for immunotherapy response.
• Limited data exists on pembrolizumab efficacy in Japanese patients with MSI-high/TMB-high prostate cancer.

Purpose of the Study:

• To report a case of successful pembrolizumab treatment in a Japanese patient with MSI-high and TMB-high prostate cancer.
• To highlight the potential benefit of genomic profiling in advanced prostate cancer.
• To document the response to pembrolizumab after multiple prior systemic treatments.

Main Methods:

• Case report of a 68-year-old male with metastatic prostate cancer.
• Genomic testing revealing MSI-high and TMB-high status.
• Treatment with pembrolizumab following progression on androgen receptor signaling inhibitors and chemotherapy.

Main Results:

• The patient achieved a marked reduction in prostate-specific antigen (PSA) levels.
• Significant shrinkage of metastatic lesions was observed.
• The patient demonstrated a positive response to pembrolizumab therapy.

Conclusions:

• Genomic testing is crucial for identifying potential candidates for targeted therapies like pembrolizumab, especially in high-grade tumors.
• MSI-high and TMB-high prostate cancer can respond favorably to pembrolizumab.
• Close monitoring for adverse events is essential during pembrolizumab treatment.