Effect of Prophylactic Cranial Irradiation on Overall Survival in Metastatic Small-Cell Lung Cancer: A Propensity Score-Matched Analysis

The role of prophylactic cranial irradiation (PCI) in metastatic small-cell lung cancer (SCLC) is controversial. Using the National Cancer Database we show that patients treated with PCI have improved survival outcomes. In light of conflicting randomized trials, this study adds information to help guide physician and patient decision-making about the utility of PCI in metastatic SCLC. Introduction: Patients with small-cell lung cancer (SCLC) have a high incidence of occult brain metastases and are often treated with prophylactic cranial irradiation (PCI). Despite a small survival advantage in some studies, the role of PCI in extensive stage SCLC remains controversial. We used the National Cancer Database to assess survival of patients with metastatic SCLC treated with PCI. Patients and Methods: Metastatic SCLC patients without brain metastases were identified. To minimize treatment selection bias, patients with an overall survival (OS) < 6 months were excluded. Cox regression identified variables associated with OS. Patients were propensity score-matched on factors associated with receipt of PCI or OS. The effect of PCI on OS was examined using Kaplan–Meier estimates. Results: In the overall cohort (n = 4257), treatment with PCI (n = 473) was associated with improved survival (hazard ratio, 0.66; 95% confidence interval, 0.60-0.74; P <.0001). Comparisons of propensity score-matched cohorts revealed a significant survival benefit for patients who received PCI in median OS (13.9 vs. 11.1 months; P <.0001), as well as 1- and 2-year OS (61.2% vs. 44.0% and 19.8% vs. 11.5%, respectively; P <.0001). This survival benefit persisted even after excluding patients who survived < 9 months (median: 15.3 vs. 12.9 months; P <.0001). In multivariable analysis, predictors of receipt of PCI were Caucasian race, younger age, and lower Charlson–Deyo score. Conclusion: Using a modern population-based data set, we showed that metastatic SCLC patients treated with PCI have significantly improved OS. This large retrospective study helps address the conflicting prospective data.