A case of double‐negative prostate cancer with BRCA2 mutation and high tumor mutation burden treated sequentially with olaparib and pembrolizumab

Introduction Double‐negative prostate cancer, an androgen receptor–independent prostate cancer without features of neuroendocrine tumors, is refractory to treatment but could be an ideal candidate for individualized treatment. Case presentation An 85‐year‐old patient with metastatic castration‐resistant prostate cancer without prostate‐specific antigen progression presented with local recurrence and liver and lung metastases 6 months after orchiectomy and apalutamide. A liver tumor biopsy led to a diagnosis of double‐negative prostate cancer. FoundationOne ® CDx showed BRCA2 mutation and high tumor mutation burden. Olaparib and pembrolizumab were administered sequentially, and the patient responded to each treatment for 5 months until radiographic progression. Conclusion Sequential use of olaparib and pembrolizumab may be effective for double‐negative prostate cancer with BRCA2 mutations and high tumor mutation burden.