What happened, in summary

A 66-year-old woman who had never smoked was diagnosed with Stage IV lung adenocarcinoma. Imaging showed a 44-mm tumor in the left upper lung, pleural disease, and a brain metastasis. Molecular testing found an EGFR L858R mutation, while PD-L1 expression was initially below 1%.

She first received gamma-knife radiation for the brain metastasis and then started osimertinib. The lung tumor shrank and the pleural fluid decreased, producing a partial response. This control lasted for almost 4 years. About 46 months after starting osimertinib, the primary lung tumor began to grow again, while no other new metastatic sites were seen.

Because the progression was limited to the lung tumor, it was surgically removed about 47 months after osimertinib began. Pathology showed that part of the tumor had transformed from adenocarcinoma into pleomorphic carcinoma, a more aggressive histologic form. The EGFR L858R mutation was still present, and PD-L1 expression had risen to above 75%.

She continued osimertinib after surgery. At 9 months of postoperative follow-up, no recurrence had been seen and she remained on osimertinib. Her course shows prolonged control of metastatic EGFR-mutant lung cancer with targeted therapy plus local treatment for isolated progression.