What happened, in summary

A 68-year-old man with a smoking history and COPD was diagnosed with Stage III lung adenocarcinoma after imaging found a large mediastinal mass and a lymph-node biopsy showed metastatic adenocarcinoma. Molecular testing found STK11, TP53, and RB1 mutations, a high tumor mutational burden, and PD-L1 expression of 70%.

He began combined radiation with carboplatin and paclitaxel. Severe neutropenia required the chemotherapy to be held during the final 2 weeks, although he completed the radiation course. Soon afterward, imaging showed disease progression with enlarging lymph nodes and a new lung mass.

Pembrolizumab was then started as second-line immunotherapy. Within 3 months, his breathing and fatigue improved and imaging showed a partial response. He tolerated treatment without significant immune-related toxicity and continued pembrolizumab for more than 2 years. The durable response was notable because STK11 alterations are often associated with more difficult treatment outcomes, while this tumor also had high PD-L1 expression and a high mutation burden.