Surgery of enlarging lesions after stereotactic radiosurgery for brain metastases in patients with non‐small cell lung cancer with oncogenic driver mutations frequently reveals radiation necrosis: case series and review

In brain metastases, radiation necrosis (RN) is a complication that arises after single or multiple fractionated stereotactic radiosurgery (SRS/FSRS), which is challenging to distinguish from local recurrence (LR). Studies have shown increased RN incidence rates in non‐small cell lung cancer (NSCLC) patients with oncogenic driver mutations (ODMs) or receiving tyrosine kinase inhibitors (TKIs). This study investigated enlarging brain lesions following SRS/FSRS, for which additional surgeries were performed to distinguish between RN and LR. We investigated seven NSCLC patients with ODMs undergoing SRS/FSRS for BM and undergoing surgery for suspicion of LR on MRI imaging. Descriptive statistics were performed. Among the seven patients, six were EGFR+, while one was ALK+. The median irradiation dose was 30 Gy (range, 20–35 Gy). The median time to develop RN after SRS/FSRS was 11.1 months (range: 6.3–31.2 months). Moreover, gradually enlarging lesions were found in all patients after 6 months post‐SRS/FSR. Brain radiation necrosis was pathologically confirmed in all the patients. RN should be suspected in NSCLC patients when lesions keep enlarging after 6 months post‐SRS/FSRS, especially for patients with ODMs and receiving TKIs. Further, this case series indicates that further dose reduction might be necessary to avoid RN for such patients.