Successful management of synchronous prostate adenocarcinoma and lung squamous cell carcinoma with sintilimab and ADT in a frail elderly patient with bronchiectasis: a case report.

Background: The management of elderly patients with multiple primary malignant neoplasms (MPMNs) presents a significant clinical challenge, requiring a balance between oncological efficacy and treatment tolerability. This case report details an elderly, non-verbal male with significant cardiopulmonary comorbidities who presented with synchronous prostate adenocarcinoma and lung squamous cell carcinoma (LUSC). The coexistence of two primary malignancies complicated by recurrent pulmonary infection is exceedingly rare in both clinical guidelines and real-world practice, making the proposed treatment strategy particularly valuable for clinical reference. Case presentation: A 74-year-old congenitally deaf-mute male with high frailty risk, complicated by hypertension, coronary heart disease and bronchiectasis with chronic Pseudomonas aeruginosa colonization, was diagnosed with synchronous prostate adenocarcinoma and lung squamous cell carcinoma (LUSC). In the available archival pathology report, immunohistochemical testing used a PD-1 mouse monoclonal antibody (clone MX033; Fuzhou Maixin Biotechnology Co., Ltd.) and showed PD-1 positivity in no more than 1% of infiltrating lymphocytes. This result does not measure PD-L1 expression on tumor cells and does not provide a tumor proportion score (TPS); the original 2024 slides were archived and no tumor-cell PD-L1 assay/TPS result was available for re-evaluation. Baseline comprehensive geriatric assessment (CGA) confirmed high chemotherapy toxicity risk, and the patient's family declined platinum-doublet intensive chemotherapy. Initial combined androgen deprivation therapy (ADT) for prostate cancer plus afatinib first-line targeted therapy for LUSC failed to control the disease, followed by progressive disease after second-line single-agent vinorelbine. Subsequently, standard-dose sintilimab (PD-1 inhibitor) monotherapy was administered as third-line treatment for LUSC with continuous ADT maintained for prostate cancer. Results: Serial radiology revealed durable marked regression of lung lesions and sustained stable prostate disease, achieving synchronous dual-tumor control. Sintilimab was prescribed on a q21-day schedule but was not delivered uninterruptedly: 12 administrations were given between December 24, 2024 and June 9, 2026, with infection-related interruptions, including a longest interval of more than 3 months. Recurrent bronchiectasis exacerbations with Pseudomonas aeruginosa infection were managed by culture-directed antibiotics and temporary interruption rather than permanent cessation of immunotherapy. No grade 2 or higher immune-related adverse events were documented during the reported follow-up, and the patient's clinical condition and tumor status were stable at the latest recorded follow-up. Conclusion: This single case describes the clinical feasibility of standard-dose sintilimab plus ongoing ADT for synchronous prostate adenocarcinoma and LUSC in a frail elderly patient who declined platinum-doublet intensive chemotherapy. The observed response occurred in the context of intermittent, infection-related treatment delays and should not be interpreted as proof of a causal immune-endocrine mechanism. Because tumor-cell PD-L1 TPS was unavailable, biomarker-based conclusions cannot be drawn. This hypothesis-generating observation may inform future studies and individualized decision-making in similarly complex patients.