Selecting Patients with Extensive-Stage Small Cell Lung Cancer for Prophylactic Cranial Irradiation by Predicting Brain Metastases

Introduction: Prophylactic cranial irradiation has recently been reported to improve overall survival and quality of life in patients with extensive-stage small cell lung cancer. The generalizability of this treatment to an unselected population with extensive-stage small cell lung cancer is not clear, as the incidence of brain metastases is variably reported in the literature, ranging from 25 to 60%. Methods: We completed a retrospective review of 130 consecutive patients with extensive-stage small cell lung cancer seen in consultation between January 1, 2004, and December 31, 2006. Our primary objective was to determine the incidence of brain metastases and to establish significant factors that were predictive of developing brain metastases, using both univariate and multivariate regression analysis. Results: The median patient age was 68.0 years, and the median survival time was 25.6 weeks. The majority of patients (84.9%) received systemic therapy. Twenty-nine patients (22.3%) presented with brain metastases while an additional 21 patients (20.8%) developed brain metastases over their lifetime. Response to chemotherapy was a predictor of brain metastases using univariate (odds ratio [OR] 5.28, p = 0.03) and multivariate analysis (OR 5.49, p = 0.04). Weight loss more than 5 kg predicted for freedom from the development of brain metastases using univariate (OR 0.20, p = 0.01) and multivariate analysis (OR 0.69, p = 0.03). Conclusions: 20.8% of patients developed brain metastases after their initial presentation. This incidence is lower than that previously reported and may suggest that prophylactic cranial irradiation should be targeted to patients at highest risk. Response to chemotherapy and less than 5 kg baseline weight loss were independent predictors of future brain metastases.