Risk of leptomeningeal carcinomatosis in patients with brain metastases treated with stereotactic radiosurgery.

There is limited available literature examining factors that predispose patients to the development of LMC after stereotactic radiosurgery (SRS) for brain metastases. We sought to evaluate risk factors that may predispose patients to LMC after SRS treatment in this case-control study of patients with brain metastases who underwent single-fraction SRS between 2011 and 2016. Demographic and clinical information were collected retrospectively for 19 LMC cases and 30 controls out of 413 screened patients with brain metastases. Risk factors of interest were evaluated by univariate and multivariate logistic regression analyses and overall survival rates were evaluated by Kaplan-Meier survival analysis. About 5% of patients with brain metastases treated with SRS developed LMC. Patients with LMC (median 154 days, 95% CI 33-203 days) demonstrated a poorer overall survival than matched controls (median 417 days, 95% CI 121-512 days, p = 0.002). The most common primary tumor histologies  that lead to the development of LMC were non-small cell lung cancer (36.8%), breast cancer (26.3%), and melanoma (21.1%). No association was found between the risk of LMC and the location of the brain lesion or total volume of brain metastases. Prior surgical resection of brain metastases before SRS was associated with a 6.5 times higher odds (95% CI 1.45-29.35, p = 0.01) of developing LMC post-radiosurgery compared to those with no prior resections of brain metastases. Additionally, adjuvant WBRT may help to reduce the risk of LMC and can be considered in decision-making for patients who have had brain metastasectomy.