Clinical outcomes of reirradiation of brain metastases from small cell lung cancer with Cyberknife stereotactic radiosurgery

Purpose: To analyze outcomes of reirradiation with stereotactic radiosurgery (SRS) for patients with brain metastases from small cell lung cancer (SCLC). Materials and Methods: We reviewed the clinical outcomes of 27 patients with brain metastases from SCLC treated with CyberKnife((R)) robotic radiosurgery (Accuray Inc., Sunnyvale, CA). Kaplan-Meier analyses were used to estimate local control (LC), intracranial control (IC), and overall survival (OS). The Graded Prognostic Assessment (GPA) prognostic index was determined with a Cox Regression analysis to model predictors of outcome. Results: The median follow-up from SRS was 12 months (2-24 months). Nine patients (32.1) had Graded Prognostic Assessment (GPA) scores 0-1 and 19 patients (67.9) had GPA scores 1.5-2.5. 19 patients (70) received whole brain radiation therapy (WBRT) and 8 patients (30) received prophylactic cranial irradiation (PCI). The median SRS dose was 20.5 Gy (15-24 Gy) in 1 fraction. Actuarial LC at 6 months and 12 months was 76.5 and 76.5, respectively. New metastases outside the treated area developed in 60 of assessable patients at a median 3.5 months; 78 received previous WBRT. The median OS was 3 months from SRS with actuarial 6-month and 12-month rates of 25 and 3.6, respectively. On multivariate analysis no factors were associated with LC, IC, or OS. Conclusions: SRS for reirradiation of brain metastases from SCLC is safe and achieves local tumor control in the majority of patients. Despite SRS, these patients are at high risk of distant brain failure.