Impact of Long‐Term Structured Exercise on Body Composition in an NTRK Fusion‐Positive NSCLC Patient Treated With Entrectinib

Entrectinib, a first‐generation TRK inhibitor, is effective in NTRK fusion‐positive non‐small cell lung cancer (NSCLC) but commonly induces significant weight gain. We describe the case of a 42‐year‐old patient with metastatic NTRK‐positive NSCLC undergoing entrectinib who participated in a two‐year, supervised exercise program. The intervention included twice‐weekly aerobic and resistance training aligned with international exercise‐oncology guidelines. Adherence was high (91.6%), and no exercise‐related adverse events occurred. Despite an initial 13 kg weight gain over 9 months, split between fat and lean mass, subsequent fat loss (~3.5 kg) occurred while lean mass was preserved. This case suggests that prolonged, structured exercise is a safe and feasible strategy to attenuate entrectinib‐associated metabolic effects and support physical function during targeted therapy in advanced NSCLC.