P1.15-017 Adoption of Prophylactic Cranial Irradiation for Extensive Stage Small Cell Lung Cancer: A Population Based Outcomes Study

The survival benefit of prophylactic cranial irradiation (PCI) in extensive stage small cell lung cancer (ES-SCLC) is unclear. This study aimed to determine the use of PCI and the factors associated with its use as well as its impact on overall survival (OS) in the Singapore population. We conducted a retrospective cohort study including patients diagnosed with ES-SCLC without brain metastases treated in the only two Singapore national cancer centers from 2003 to 2010. We identified the patients using the institutions’ pathology registries and linked the electronic medical records to the National Death Registry. We used multivariable logistic regression to identify factors associated with the use of PCI and its impact on OS. All analyzes were performed using STATA version 11.0. We identified 224 eligible patients. 65 of 224 patients did not receive chemotherapy. 71 of 159 patients had at least stable disease (SD) after first line chemotherapy. 16 of these 71 patients received PCI. There was an increase in the use of PCI from the period 2007 to 2010 compared with 2003 to 2006 (13 patients versus 3 patients, chi-square P value = 0.01). The use of consolidation thoracic radiation therapy (TRT) was associated with use of PCI (odds ratio 18.3, 95% confidence interval (CI) 4.70 to 71.96, P value (P) <0.001). PCI improved OS (adjusted hazard ratio 0.47, 95% CI 0.24 to 0.91, P = 0.02) compared to no PCI use among the 71 patients who had at least SD after first line chemotherapy. Consolidation TRT did not improve OS among this group of patients. The utilization rate of PCI remained low in the Singapore population between 2003 and 2010 despite an increase in its use since 2007. Patients who had at least SD after first line chemotherapy or had consolidation thoracic radiation therapy were more likely to receive PCI. Among patients who had at least stable disease after first line chemotherapy, the use of PCI was associated with an improved survival outcome.