Lung Adenocarcinoma That Transformed to Small Cell Cancer After Recurrence

What happened, in summary

A 67-year-old man with a long smoking history underwent a right upper lobectomy in March 2022 and was diagnosed with Stage III lung adenocarcinoma. PD-L1 expression was low to moderate, and no druggable driver alteration was identified. After surgery, he received 4 cycles of cisplatin and vinorelbine followed by adjuvant atezolizumab.

In July 2023, he developed vision loss on one side and weakness. Brain imaging found a metastatic tumor in the occipital lobe. The tumor was surgically removed and then treated with radiation. Pathology showed small cell lung cancer rather than the original adenocarcinoma, supporting transformation of the lung cancer into a small-cell form. Imaging also found multiple liver metastases, making the recurrent disease Stage IV.

He then received 4 cycles of cisplatin and etoposide with the immunotherapy durvalumab, followed by maintenance durvalumab. The metastatic disease regressed and remained controlled. By September 2024, he had reached 13 months without further progression on this treatment approach.

The case shows how lung cancer can change histology during treatment. Rebiopsy of the recurrent brain lesion was important because it identified small-cell transformation and led to a different treatment strategy than would have been used for recurrent adenocarcinoma alone.