Prophylactic Cranial Irradiation (PCI) and Consolidative Thoracic Radiation (TRT) in Extensive Stage Small Cell (ES-SCLC) Lung Cancer

Abstract

Small cell lung cancer accounts for 10-15% of all lung cancers. Majority of patients present with extensive stage disease (ES-SCLC). Two-year survival is poor, with median survival ranging from 7-10 months. The role of PCI remains controversial in ES-SCLC given conflicting results from randomized trials. Similarly, routine thoracic radiation (TRT) while had shown significant benefit in improving local control, given high incidence of systemic recurrence has not been adopted widely. It has been our practice to consider PCI and TRT in patients with no evidence of disease progression after initial chemotherapy. Here, we report our single institution retrospective analysis of patients undergoing PCI or intrathoracic radiotherapy after chemotherapy. Patients with ES-SCLC diagnosis who did not have brain metastasis at initial diagnosis and completed initial chemotherapy from 2009–2018 are included with IRB approval. We collected demographic information, sites of metastatic disease, and treatment details. Survival analysis was performed using Kaplan-Meier estimates with log-rank testing for comparison. We evaluated use of PCI, TRT, age, race and number of sites of disease for overall survival. From our small cell lung cancer database, 137 patients met the criteria and are included in the analysis. The median age was 65.6 years (43 – 91) with 70% being males and 73% being white race. 56 patients received TRT and 34 patients received PCI. The median TRT dose was 32.5 Gy (20 – 60 Gy). Liver (51%) was most common metastatic site followed by bone, 36%. The median overall survival for all patients was 9 months, with 12- and 18-month survival being 31.6% and 11.8%. The median overall survival with PCI was 13 months compared to 7 months with no PCI (p<0.0001). Similarly, TRT improved median survival to 12 months versus 6 months without (p<0.003). The overall survival of patients receiving both PCI and TRT compared to none was 13 vs 5 months (p = 0.0001). Patients receiving PCI or TRT, younger age ≤ 65 years had improved median OS compared to > 65 years, 14 vs 11 months (p = 0.026). Race, sex and number of metastatic sites were not significant. Our single institutional result suggested benefit of both PCI and TRT in these patient populations who had any response to chemotherapy. Recently, the addition of immune check point inhibitor to platinum-etoposide in ES-SCLC have shown improvement in median survival from 10 to 13 months. Future trials are needed to evaluate the role of PCI and TRT in combination with chemo-immunotherapy.