LG-03 * RADIATION THERAPY IS ASSOCIATED WITH INCREASED LATE MORTALITY IN LONG-TERM ADULT SURVIVORS OF CHILDHOOD LOW GRADE GLIOMA: A POPULATION BASED STUDY

Abstract

PURPOSE: To uncover clinical risk factors and the impact of radiotherapy on children and adult survivors of childhood low grade glioma (PLGG). METHODS: We collected long-term follow-up information for all PLGG patients diagnosed in all Ontario, Canada from 1985–2012 (n = 1202) and determined factors affecting long-term survival. The impact of upfront (first line) radiation treatment on overall survival was determined in a discovery cohort of clinically relevant (incompletely resected) Ontario PLGG patients and an independent population based validation cohort from the Surveillance, Epidemiology and End Results (SEER) database (n = 2402). RESULTS: At a median follow-up of 12.73 (0.02-33) years; only 93 deaths (7.7%) were recorded with 20 years overall survival (OS) of 90.1% + 1.1%. Children with NF1 had excellent survival and no tumor-related deaths during adulthood. Adverse risk factors included pleomorphic xanthoastrocytoma tumor type (p 5 years post-diagnosis, upfront radiotherapy was associated with three-fold increased risk of overall late deaths (p = 0.001) and four-fold increased risk of tumor-related deaths (p = 0.013). On multivariate analysis radiation therapy was the most significant factor associated with late all deaths and tumor-related deaths (HR 3 [1.3–7.0; p = 0.012] and HR 4.4 [1.3–14.6; p = 0.014] respectively). Similar association of radiotherapy and late deaths was observed in the validation cohort (p < 0.001). In contrast to early deaths, late mortality was not associated with PLGG progression but rather tumor transformation (54%), secondary malignancy (11%) and other non-oncological causes (35%). CONCLUSION: The chronic clinical course of PLGG is associated with excellent long-term survival and is hampered by increased delayed mortality in patients receiving upfront radiotherapy. These observations should be considered while deciding treatment options for these patients.