Unexpected Fatal Pneumocystis Jirovecii Pneumonia During Triplet Therapy for Hormone‐Sensitive Prostate Cancer

Pneumocystis jirovecii pneumonia (PJP) is a life‐threatening opportunistic infection typically seen in immunocompromised patients. It is rarely reported during standard systemic therapy for prostate cancer. A 75‐year‐old man with low‐volume metastatic hormone‐sensitive prostate cancer (mHSPC) received triplet therapy with relugolix, darolutamide and docetaxel. He had well‐controlled diabetes and no history of immunosuppression. After the second docetaxel cycle, he developed anorexia. Chest CT revealed bilateral ground‐glass opacities. β‐D‐glucan was elevated, and sputum PCR detected P. jirovecii DNA. Despite appropriate trimethoprim‐sulfamethoxazole and corticosteroid therapy, he died of respiratory failure ~10 days after symptom onset. This case highlights an underrecognized risk of PJP during triplet therapy for mHSPC. Prophylaxis should be considered in select high‐risk patients, including elderly individuals or those with metabolic comorbidities.