What happened, in summary

A 56-year-old man who smoked sought care for more than a month of persistent cough and coughing up blood. CT showed a mass in the left upper lung. A needle biopsy was inconclusive, and within 2 months the mass had grown rapidly with a second nearby lesion.

He underwent left upper lobectomy with systematic lymph-node dissection. Surgical pathology confirmed Stage III large cell carcinoma of the lung. Molecular testing did not identify an actionable mutation, while PD-L1 expression was high at more than 60%.

Only 1 month after surgery, follow-up imaging showed enlargement of left hilar and mediastinal lymph nodes, consistent with recurrence. He then received 3 cycles of chemotherapy combined with pembrolizumab. Because chemotherapy side effects were difficult to tolerate, chemotherapy was stopped and pembrolizumab was continued alone for another 21 cycles.

The enlarged lymph nodes rapidly shrank, and later imaging showed a complete response. He remained progression-free throughout the 24 treatment cycles, with pembrolizumab tolerated without severe adverse events. His course shows a strong and sustained response to immunotherapy after an unusually early recurrence of a rare large cell lung cancer.