Synchronous Stage IA lung adenocarcinoma and grade 4 glioblastoma: lung nodule regressed during brain-cancer therapy

What happened, in summary

This 75-year-old Japanese woman, a never-smoker, was found to have 2 separate primary cancers during the same evaluation. Brain MRI showed a 47 mm mass extending from the left cerebellar hemisphere to the medulla oblongata. Whole-body CT also found an 18 mm spiculated nodule in the right lower lung. Craniotomy for diagnostic biopsy and bronchoscopy confirmed 2 different diseases: CNS WHO grade 4 glioblastoma in the brain and Stage IA lung adenocarcinoma in the lung. The brain tumor was not a lung metastasis. Because glioblastoma was the more immediately aggressive cancer, her team prioritized CNS-directed therapy. She underwent maximum safe surgical resection of the brain tumor, followed by concurrent temozolomide and intensity-modulated radiotherapy, 40.05 Gy in 15 fractions. Adjuvant temozolomide was then given every 28 days, with dose escalation. A new contrast-enhancing brain lesion appeared about 4 weeks after the initial response, so bevacizumab was added to temozolomide. The lung adenocarcinoma was not treated directly during this period. Even so, the lung nodule decreased from 18 mm at diagnosis to 12 mm by week 13, before bevacizumab, and then to 9 mm by week 19 after combined temozolomide and bevacizumab. As of March 2026, she remained alive without lung-cancer progression while continuing care for glioblastoma. The case is unusual because the lung cancer improved during treatment aimed at the brain tumor, not during surgery, radiation, or targeted therapy for the lung. Her lung tumor remained Stage IA, while most of the active treatment burden came from the separate CNS cancer.