A volume matched comparison of survival after radiosurgery in non-small cell lung cancer patients with one versus more than twenty brain metastases

Background Treatment of patients with a large number of brain metastases using radiosurgery remains controversial. In this study we sought to conduct a volume matched comparison to evaluate the clinical outcome of patients with > 20 brain metastases and compared it with patents with solitary brain tumor form non-small cell lung cancer (NSCLC). Methods Between 2014 and 2020, 26 NSCLC patients (925 tumors) underwent stereotactic radiosurgery (SRS) for > 20 metastases in a single procedure (median margin dose = 16 Gy, median cumulative tumor volume = 4.52 cc); 56 patients underwent SRS for a single metastasis (median margin dose = 18 Gy, median volume = 4.74 cc). The overall survival (OS), local tumor control (LC), adverse radiation effect (ARE) risk, and incidence of new tumor development were compared. Results No difference in OS was found between patients with > 20 brain metastases (median OS = 15 months) and patients with solitary metastasis (median OS = 12 months; p = 0.3). In the solitary tumor cohort, two of 56 (3.5%) tumors progressed whereas in the > 20 cohort only 3 of 925 (0.3%) tumors showed progression (*p = 0.0013). The rate of new tumor development was significantly higher in patients with > 20 tumors (***p = 0.0001). No significant difference of ARE rate was found (7.5% for > 20 tumors vs. 8.7% for single metastasis). Conclusions Patients with > 20 tumors showed significantly better LC with similar OS compared to patients with solitary tumors. Current guidelines that restrict the role of SRS to patients with 1-4 tumors should be revised.