Prophylactic cranial irradiation in small-cell lung cancer: is it ever indicated?

Prophylactic cranial irradiation (PCI) is being reintroduced into multimodality treatment protocols of patients with small-cell lung cancer (SCLC). The history of its use brings interesting insights into clinical evaluations of treatment strategies and design of relevant and informative trials. The critical issues of effectiveness and overall health gains of prophylactic cranial irradiation have been addressed in a series of recently completed clinical trials. These trials tested prophylactic cranial irradiation in small-cell lung cancer patients achieving good response to induction therapy and confirmed the ability of standard prophylactic cranial irradiation schedules to significantly reduce the lifetime risk of brain metastases. A subset of these trials evaluated neurotoxicity in a formal and prospective manner. No sustained or significant detriment in neuropsychometric function could be linked to the use of prophylactic cranial irradiation. In addition, all the large trials have shown a consistent survival advantage in favor of the prophylactic cranial irradiation arm. None of the individual sample sizes were large enough to statistically confirm this survival benefit, but a meta-analysis is in progress and will report on this aspect of evidence shortly. Issues that remain to be answered are the optimal dose and schedule of prophylactic cranial irradiation as well as the timing of this administration. These questions form the nucleus of the next generation of collaborative trials that are being designed.