RADT-15. CLINICAL OUTCOMES OF PATIENTS WITH BRAIN METASTASES FROM SMALL CELL LUNG CANCER TREATED WITH STEREOTACTIC RADIOSURGERY

Abstract BACKGROUND Whole brain radiation therapy (WBRT) has historically been standard treatment for brain metastases (BM) from small cell lung cancer (SCLC). Stereotactic radiosurgery (SRS) is increasingly used as an upfront approach. We report institutional outcomes for patients with SCLC treated with SRS for BM. METHODS Patients who underwent single fraction SRS for intact BM from 2002-2025 were identified from a single institution IRB-approved database. Patients with less than one month of follow-up were excluded. Primary endpoint was local control (LC); secondary endpoints were freedom from distant brain failure (FFDBF) and overall survival (OS). Survival analysis was performed using Kaplan-Meier Method. Cox regression identified predictors of LC. RESULTS The study included 135 patients with 429 BM. Median follow-up was 5.2 months. Median prescription dose was 22Gy (IQR: 20-24Gy). Eighty-five BM with median size 2.6cm (IQR: 2.1-3.4cm) received <20Gy. Of these, 22 (26%) BM underwent staged SRS to 30Gy total. Twenty-six patients with 63 BM (14%) underwent upfront SRS, 43 patients with 105 BM (24%) had prior prophylactic cranial irradiation (PCI), 64 patients with 249 BM (58%) had prior WBRT, and two patients with 12 BM (3%) had both PCI and WBRT. Thirty-two patients with 112 BM (26%) received concurrent systemic therapy (within two weeks of SRS). One-year LC, FFDBF, and OS were 89%, 21%, and 26%, respectively. For BM receiving ≥20Gy, 30Gy (staged), and <20Gy, one-year LC was 91%, 88%, and 74%, respectively. Prescription dose ≥20Gy or staged SRS to 30Gy was significantly associated with improved LC (p<0.01), while prior PCI/WBRT (p=0.41) and concurrent systemic therapy (p=0.77) were not. CONCLUSIONS LC with SRS for BM from SCLC, including for recurrence after PCI/WBRT, is comparable to those of other histologies. OS remains limited due to systemic progression. Prescription dose ≥20Gy or staged SRS to 30Gy should be considered when feasible.