Five-fraction stereotactic radiosurgery (SRS) for single inoperable high-risk non-small cell lung cancer (NSCLC) brain metastases

Abstract

Background: Achieving durable local control while limiting normal tissue toxicity with definitive radiation therapy in the management of high-risk brain metastases remains a radiobiological challenge. The objective of this study was to examine the local control and toxicity of a 5-fraction stereotactic radiosurgical approach for treatment of patients with inoperable single high-risk NSCLC brain metastases. Methods: This retrospective analysis examines 20 patients who were deemed to have "high-risk" brain metastases. High-risk tumors were defined as those with a maximum diameter greater than 2cm and/or those located within an eloquent cortex. Patients were evaluated by a neurosurgeon prior to treatment and determined to be inoperable due to tumor or patient characteristics. Patients were treated using the CyberKnife® SRS system in 5 fractions to a total dose of 30Gy, 35Gy, or 40Gy. Results: Twenty patients with a median age of 65.5years were treated from April 2010 to August 2014 in 5 fractions to a median total dose of 35Gy. At a median follow up of 11.3months local tumor control was observed in 18 of 20 metastases (90%). Both local failures were observed in patients receiving a lower dose of 30Gy. Median pre-treatment dexamethasone dose was 10mg/day and median post-treatment nadir dose was 0mg/day. Salvage intracranial therapy was required in 45% of patients. Symptomatic radionecrosis was observed in 4 of 20 patients (20%), two of which were treated to 40Gy and the remainder to 35Gy. Kaplan-Meier 1-year, 2-year, and median survival were calculated to be 45%, 20%, and 13.2months, respectively. Conclusions: Five-fraction SRS to a total dose of 35Gy appears to be a safe and effective management strategy for single high-risk NSCLC brain metastases, while a total dose of 40Gy leads to an excess risk of neurotoxicity.