Prophylactic cranial irradiation in complete responders with small-cell lung cancer: analysis of the Mayo Clinic and North Central Cancer Treatment Group data bases.

Abstract

PURPOSE To determine whether prophylactic cranial irradiation (PCI) has an impact on brain failure and survival in patients with small-cell lung cancer (SCLC) who have achieved a complete response to chemotherapy with or without thoracic radiation therapy (TRT). METHODS Between 1975 and 1990, the Mayo Clinic and North Central Cancer Treatment Group entered 1,617 patients on 15 phase II and III SCLC protocols of chemotherapy with or without TRT and PCI. RESULTS Of 772 patients with limited disease, 457 (59%) achieved a complete response, compared with 200 of 845 patients (24%) with extensive disease. With follow-up durations of 2 to 17 years (median, 4), the median survival time and 2-, 5-, and 10-year survival rates for the 457 completely responding limited-disease (LD-CR) patients were 19.6 months, 41%, 17%, and 5%, compared with 13.9 months, 26%, 8%, and 5%, respectively, for the 200 completely responding extensive disease (ED-CR) patients (P = .0001). Multiple prognostic factors, including whether the patient did or did not receive PCI (30 to 38 Gy in 2- to 3.6-Gy fractions) were analyzed. In both univariate and multivariate analyses, PCI was not associated with improved (or worsened) survival. The brain relapse rate was 37% for LD-CR patients who did not receive PCI versus 9% for those who did (P = .0001). In ED-CR patients, the brain relapse rate was 31% without PCI and 8% with (P = .009). Essentially all patients who developed brain relapse died within 2 years, with a median survival time of 3.7 months following relapse. Severe, life-threatening, or fatal CNS toxicity occurred in approximately 3% of patients who received PCI. CONCLUSION The use of PCI remains controversial outside the setting of a clinical trial.