A Prospective, Single-center, Non-randomized, Interventional Study on the Effectiveness and Safety of Combined Immunotargeted Therapy in Patients With Metastatic Non-small Cell Cancer With a RET Gene Translocation

This interventional study will evaluate the effectiveness, safety, and tolerability of pembrolizumab in combination with lenvatinib in adults with metastatic non-small cell lung cancer (NSCLC) who have a confirmed RET gene rearrangement and whose disease has progressed after one or more previous systemic treatments. Participants will receive pembrolizumab intravenously once every 3 weeks in combination with lenvatinib taken by mouth daily until disease progression, unacceptable side effects, or treatment discontinuation. Tumor response will be assessed using imaging studies according to RECIST 1.1, and participants will be monitored for treatment-related side effects, progression-free survival, and overall survival. The study will also evaluate clinical and tumor characteristics, RET rearrangement variants, and the diagnostic methods used to confirm RET-positive status.