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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.

Introduction While immune checkpoint inhibitors represent the mainstream treatment for metastatic renal cell carcinoma, a standardized approach following immune checkpoint inhibitors remains unclear. We report a case of metastatic renal cell carcinoma treated with nivolumab rechallenge. Case presentation A 60‐year‐old male with metastatic melanoma was referred to the urology division due to right renal cancer. He was undergoing nivolumab treatment for metastatic melanoma. Radical nephrectomy revealed clear cell renal cell carcinoma, pT3a. Two months post‐surgery, multiple metastases were identified. Despite subsequent administration of interferon‐α, axitinib, and temsirolimus, the metastases progressed. Consequently, nivolumab rechallenge and palliative radiotherapy were initiated, resulting in a durable response for 20 months. However, disease progression occurred, and he died of cancer 4 years after nephrectomy. Conclusion This is the first report of nivolumab rechallenge in metastatic renal cell carcinoma. Although the utility remains unclear, this case suggests that some patients may benefit from nivolumab rechallenge.