What happened, in summary

A 61-year-old man who had never smoked presented in April 2023 after CT showed a solid 2.9 cm mass in the right middle lobe, with pleural traction and signs of vascular invasion. A fourth mediastinal lymph node was enlarged to 2.7 cm. PET/CT showed FDG uptake in both the lung mass and the mediastinal node. A small left supraclavicular lymph node was also seen, but it did not have increased metabolic uptake, so metastasis could not be confirmed. Needle biopsy of the lung mass showed invasive adenocarcinoma. Next-generation sequencing identified a BRAF V600E mutation with a SETD co-mutation. PD-L1 tumor proportion score was 80%, tumor mutational burden was 1 mutation per megabase, and the tumor was microsatellite stable. Because the supraclavicular node was too small to biopsy, the initial stage was considered either IIIA cT2N2M0 or IIIB cT2N3M0. After multidisciplinary review, the patient chose induction targeted therapy with BRAF and MEK inhibitors rather than chemotherapy, radiotherapy, or immunotherapy. Treatment was well tolerated, with no reported treatment-related adverse events. After about 2 months, CT showed marked shrinkage of the lung mass to 1.2 cm and the mediastinal node to 0.9 cm, meeting partial response criteria. Repeat PET/CT showed no suspicious change or uptake in the supraclavicular node, so the final stage was IIIA cT2N2M0. In July 2023, he underwent video-assisted thoracoscopic right middle-lobectomy with systematic lymph-node dissection. Pathology showed a complete pathologic response, with no metastatic cancer in removed lymph nodes. As of March 2024, no recurrence or metastasis had been observed.