Interstitial pneumonia after regression by olaparib for neuroendocrine prostate cancer with mutation: a case report.

A 67-year-old man with metastatic prostate cancer was treated with leuprorelin and enzalutamide, but presented radiographic progression after 1 year. Although docetaxel chemotherapy was initiated, liver metastasis appeared with elevation of nerve-specific enolase in serum. Pathological findings of needle biopsy of lymph node metastasis in the right inguinal region showed neuroendocrine carcinoma. FoundationOne CDx using a biopsy sample of the prostate at initial diagnosis detected the mutation (deletion of intron 3-7), but BRACAnalysis test revealed no mutation in germline. Then, olaparib treatment was initiated, resulting in remarkable remission of tumors, but comorbidity with interstitial pneumonia. This case suggested that olaparib could be effective for neuroendocrine prostate cancer with gene mutation, but may cause interstitial pneumonia.