Value of prophylactic cranial irradiation given at complete remission in small cell lung carcinoma

The optimal use of "prophylactic" cranial irradiation (PCI) in patients with small cell lung cancer remains undetermined. This study reviews the impact of PCI, given at complete remission (CR), on neurologic relapse in 172 consecutive patients with small cell lung cancer treated in three sequential chemotherapy protocols at the University of Maryland Cancer Center. In the first study of 38 patients, none received PCI. In the second study of 109 patients, the first 28 achieving CR were randomized to 3000 rad of PCI in ten fractions (PCI+) or to observation (PCI-). Thereafter, based on interim analysis, all patients achieving CR received PCI. In the third study, to date, 25 patients achieving CR have received PCI. Overall, 169 patients were evaluable for neurologic relapse, and 30 of 90 patients achieving CR received PCI. Among all patients with CR, with adjustment for disease extent, there was a significant delay to any neurologic relapse (P = 0.01) and cerebral metastases (P = 0.02) for PCI+ compared to PCI- patients. Among PCI- patients with CR, cerebral metastases alone occurred in 28% as the sole site and in 33% as the initial site, whereas cerebral relapse occurred prior to systemic relapse in only one PCI+ patient with CR. Patient survival however, was not significantly altered by PCI. PCI at CR confers effective and worthwhile local control in the CNS, especially during periods of systemic response, and a small percentage of patients may benefit. Systemic drug resistance still determines overall survival.