305 Lymphopenia Predicts Response to Stereotactic Radiosurgery for Brain Metastases in Lung Cancer Patients

Abstract

INTRODUCTION: Stereotactic radiosurgery (SRS) can enhance immune activation and improve disease control through the abscopal effect. Effective anti-tumor immunity relies on a competent immune system. Patients with cancer receiving chemotherapy are often immuno-suppressed, which may impact the efficacy of SRS. Here we investigate the relationship between systemic lymphopenia and response to SRS in patients with brain-metastatic lung cancer. METHODS: We reviewed 125 cases of lung cancer brain metastases treated with SRS between January 2014 and May 2017. Complete blood counts from the time of SRS were reviewed, and lymphopenia was defined as an absolute lymphocyte count < 1000/μL. The Kaplan-Meier method and cox proportional-hazards model were used to evaluate risks of progression or death. RESULTS: The median age was 65 yr (range: 43-86), with 54% female patients. Fifty-six patients (45%) underwent prior surgical resection. The median duration of follow-up was 11.7 mo. Lymphopenia was present in 60 patients (48%). In univariate analysis, the median progression-free survival (PFS) and overall survival (OS) were significantly shorter in lymphopenic patients (PFS: 3.7 vs 9.4 mo, P