Gamma knife radiosurgery for patients with brain metastases from non–small cell lung cancer: Comparison of survival between <5 and ≥5 metastases

BACKGROUND: Current evidence‐based guidelines support stereotactic radiosurgery (SRS) for patients with up to four brain metastases (BMs). However, debate continues about how many tumors may be treated by SRS alone. METHODS: This retrospective study included non–small cell lung cancer (NSCLC) patients with BMs treated with gamma knife as the initial treatment for cerebral lesions. The patients were followed up to obtain their survival information. The outcomes were statistically analyzed to compare the differences in survival between the <5 BMs and ≥5 BMs groups and to identify prognostic factors. RESULTS: A total of 77 patients were divided into two groups (54 patients with <5 BMs and 23 patients with ≥5 BMs). The median overall survival (OS) was 18.3 months in the <5 BMs group and 17.7 months in the ≥5 BMs group. The median intracranial progression‐free survival (IPFS) was 9.0 months in the <5 BMs group and 9.9 months in the ≥5 BMs group. There was no significant difference in OS and IPFS between the two groups. The multivariate analysis demonstrated that adenocarcinoma, controlled primary cancer, higher Karnofsky Performance Scale (KPS), and salvage treatment were independent prognostic factors favoring longer OS. CONCLUSION: SRS alone as the initial treatment for NSCLC patients with more than four BMs was non‐inferior to SRS for those with one to four BMs in terms of OS and IPFS.