BACKGROUND: Prophylactic cranial irradiation (PCI) has become a standard option for patients with extensive-stage small cell lung cancer (ES-SCLC). The Cancer and Leukemia Group B 30504 trial was a randomized phase II study of the effect of sunitinib versus placebo in ES-SCLC patients responding to platinum-based systemic therapy. The study required preenrollment brain imaging. PCI was provided at the discretion of treating physicians. We performed a secondary analysis of the Cancer and Leukemia Group B trial to determine the impact of PCI on patients with ES-SCLC. METHODS: Fisher's exact test and the Wilcoxon rank-sum test were conducted to identify the differences between patients receiving PCI and patients not receiving PCI. Kaplan-Meier analyses described progression-free survival (PFS) and overall survival (OS) for patients in the PCI and non-PCI groups. RESULTS: A total of 85 patients received maintenance therapy (41 received placebo and 44 received sunitinib). Patient characteristics were balanced between the PCI and non-PCI groups. The patients receiving PCI plus sunitinib had a nonsignificant 2.7-month improvement in PFS (5.0 months versus 2.3 months, p = 0.14, hazard risk [HR] = 0.62, 95% confidence interval [CI]: 0.33-1.18) trending toward improved OS (8.9 months versus 5.4 months, p = 0.053, HR = 0.47, 95% CI: 0.22-1.03). PCI was associated with a trend toward improved median PFS (2.9 months versus 2.2 months, p = 0.096, HR = 0.69, 95% CI: 0.45-1.07) but not median OS (8.3 months in the PCI group versus 8.7 months in the non-PCI group, p = 0.76, HR = 1.07, 95% CI: 0.67-1.71). The patients receiving placebo had no improvement in PFS or OS with PCI. CONCLUSIONS: Trends toward improved PFS and OS were seen in patients receiving PCI and sunitinib, thus supporting the need for further prospective research evaluating the integration of maintenance systemic therapy and PCI for patients with ES-SCLC. Improved outcomes for patients with ES-SCLC after induction chemotherapy may require PCI, thoracic radiotherapy, and maintenance systemic therapy to achieve control of both intracranial and extracranial disease.