LAUSR

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). 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. 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). 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.