Stereotactic Radiosurgery as a Component of Treatment for Brain Metastases in Small Cell Lung Cancer Patients

Abstract

Small cell lung cancer (SCLC) aggressively metastasizes to the brain with a poor prognosis. Whole brain radiation therapy (WBRT) is the current standard of care based on historical treatment paradigms. Stereotactic radiosurgery (SRS) is known to preserve quality of life and increase intracranial local control compared to WBRT alone for non-SCLC and other non-lung histologies. Here we report outcomes and failure patterns for SRS used as upfront or salvage therapy for SCLC. The charts of 44 patients with brain metastases from SCLC who underwent SRS as either primary or salvage therapy at a single institution from 2001-2017 were retrospectively reviewed as part of an institutional review board approved study. Demographic data, use of prior prophylactic cranial irradiation (PCI) or WBRT, type of first failure (local vs. elsewhere brain), and dates of treatment failure and death were recorded. Kaplan-Meier survival analysis was used to estimate overall survival (OS) and neurologic progression-free survival (nPFS) from SRS date. Median patient age at was 63.5 years (range = 34 – 86). 5 patients (11%) had prior PCI, 24 (55%) had prior WBRT and 10 (23%) had both prior to salvage SRS. 5 patients (11%) had SRS as upfront treatment. Median number of treated lesions was 3 (range = 1-12). Median SRS tumor volume was 0.173 cubic centimeters (range = 0.007 – 22.99). Median marginal dose was 18 Gy (range = 8-21) to the 50% isodose line. First brain failure post-SRS was elsewhere in 25 patients (57%), local in 4 patients (9%), and the remainder of patients (34%) were controlled at last follow up. Median OS was 7.6 months (95% CI: 6.1-9.1) for all patients. Median nPFS was 3.7 months (95% CI: 2.5-4.9) for all patients and 9.2 months (95% CI: 4.2-14.2) for upfront SRS patients. SRS effectively salvaged or primarily treated SCLC brain metastases with a median overall survival similar to those with newly diagnosed brain metastases from other histologies. Future analysis of this dataset will study prognostic factors for PCI or WBRT failure. Prospective studies evaluating upfront SRS for SCLC are warranted.