BIOM-57. PERITUMORAL EDEMA AS A PREDICTOR OF PD-1 EXPRESSION IN BRAIN METASTASES

Abstract Brain metastases represent a significant problem in oncology with associated high morbidity and mortality. They have been associated with increased peritumoral edema which can worsen neurological symptoms and patient outcomes. Peritumoral cerebral edema may be an important metric of interest as some MRI studies have suggested an association between molecular factors and peritumoral edema. We hypothesized that an association exists between PD-1 expression in brain mets from NSCLC and the radiographic peritumoral edema to enhancing tumor ratio (ETR). A retrospective analysis of tumor characteristics was conducted to identify patients with brain metastases from non-small cell lung cancer. Patients were stratified into three groups based on their tumor PD-1 expression levels: 0%, 1-49%, and 50% or higher. Tumor and edema volumes were measured in these patients using MRIs at the time of diagnosis and converted into edema to tumor ratios. Radiographic analysis has been completed for 19 patients with 9 having no PD-1 expression, 5 having low PD-1 expression, and 5 having high PD-1 expression. The no expression group had an average ETR of 3.02 while the low expression group had an average of 15.85 and the high expression group had an average of 9.12. These initial results show increased peritumoral edema in tumors with PD-1 expression when compared to tumors with no PD-1 expression, with a non-significant trend in favor of increased edema to tumor ratio (p = 0.055). The current project is ongoing with plans to expand patient cohorts to affirm or rule out significant ETR association by MRI.