What happened, in summary

A 73-year-old man was referred with tumors in the left lower lung and small intestine. His performance status was initially good, but obstructive pneumonia and bowel obstruction developed during evaluation. He underwent resection of the left lower lobe and the affected segment of small intestine.

Pathology showed pleomorphic carcinoma arising in the lung with small-intestinal metastasis. The cancer was classified cT4N0M1a, stage IVA. Testing found no EGFR, ALK, or ROS1 driver alteration. PD-L1 expression was high, with a tumor proportion score of 80% to 90%.

After surgery, the disease continued to spread. Pleural dissemination and an abdominal subcutaneous metastasis became visible. The abdominal lesion was treated with radiation to 45 Gy in 25 fractions, and pembrolizumab monotherapy was started at 200 mg.

Assessment after two cycles showed no treatment response. Despite the high PD-L1 result, the aggressive pleomorphic carcinoma continued to progress. He died four months after pembrolizumab was initiated. Despite strong PD-L1 expression, pembrolizumab did not control his rapidly progressing cancer.