In 1999, Aupérin and colleagues1 established the role of prophylactic cranial irradiation (PCI) in small cell lung cancer (SCLC) complete responders based on 7 randomized clinical trials with enrollment periods from 1977 to 1995. At initial diagnosis, a minority of the study population presented with extensive disease. A European Organisation for Research and Treatment of Cancer trial published in 2007 endorsed the role of PCI in extensive-stage (ES)–SCLC.2 Both analyses, however, took place in the era before the routine use of brain magnetic resonance imaging (MRI) for staging SCLC; thus, critics believe that the moderate but significant survival benefit conferred by delivery of PCI is in part due to the eradication of subclinical brain metastases (BMs). The debate on PCI within the thoracic oncology community was fueled by a recent multicenter phase 3 trial by Takahashi and colleagues3 that failed to show an overall survival benefit of PCI vs observation for patients with ES-SCLC who underwent comprehensive MRI surveillance and treatment of occult BMs on detection.