Excellent Outcomes with Radiosurgery for Multiple Brain Metastases in ALK and EGFR Driven Non-Small Cell Lung Cancer

Introduction: Patients with brain metastases (BMs) arising from EGFR-mutated and anaplastic lymphoma kinase gene (ALK)-rearranged NSCLC have a favorable prognosis compared with patients with non-oncogene-addicted NSCLC, emphasizing the importance of minimizing toxicities such as the cognitive sequelae of whole brain radiation therapy (WBRT). Although radiosurgery without WBRT is the preferred strategy for one to three BMs, this paradigm remains controversial for patients with multiple BMs.

Methods: We reviewed the cases of patients with EGFR-mutated and ALK-rearranged NSCLC presenting to our cancer center between 2008 and 2017 and included only patients receiving treatment to four or more BMs in a single radiosurgery session.

Results: We identified 35 patients with a median follow-up of 4.1 years. The maximum number of BMs treated in a single radiosurgery session ranged from four to 26 (median number of BM treated per radiosurgery course: 6), and in total over all courses the number ranged from four to 47 (median: 10). The median survival was 3.0 years (4.2 for ALK-rearranged NSCLC; 2.4 for EGFR-mutated NSCLC) from the diagnosis of BM, and survival was comparable regardless of number of radiosurgery courses, number of BMs treated in total, or number of BMs treated in a single radiosurgery session. The mean hippocampal and whole-brain doses were exceedingly low even for patients receiving treatment to more than 10 BMs (1.2 and 0.8 Gy, respectively). Radiosurgery was well tolerated overall and the 5-year rate of freedom from neurologic death was 84%. The 5-year rate of freedom from WBRT was 97%.

Conclusions: Radiosurgery for multiple BMs is controversial, yet patients with EGFR-mutated and ALK-rearranged NSCLC may be uniquely suited to benefit from this approach. These results support single and multiple courses of radiosurgery without WBRT for patients with oncogene-addicted NSCLC with four or more BMs.