What happened, in summary

A 72-year-old man with a 50 pack-year smoking history developed worsening shortness of breath and weight loss. CT showed large masses in the left lower lung and right upper lung. Because biopsy of the right mass carried a high risk of pneumothorax, only the left tumor was sampled. It was adenocarcinoma without a detected driver-gene mutation, and PD-L1 expression was very high, with a tumor proportion score of 100%.

The bilateral findings were initially managed as one advanced adenocarcinoma, although clinicians considered the possibility of separate primary lung cancers. Pembrolizumab 200 mg every 3 weeks began on December 16, 2017. The left lower-lung tumor rapidly shrank and ultimately disappeared completely.

In contrast, the right upper-lung mass continued to grow and was later confirmed as a separate small cell lung cancer. The patient's overall condition deteriorated, and he died on March 8, 2018. An autopsy the next day found no remaining tumor in the left lung, confirming a complete response of the adenocarcinoma. His death occurred in the setting of progression of the separate right-sided cancer.