Supratentorial Primitive Neuroectodermal Tumors (PNETs) and Medulloblastoma in Children and the Elderly: A Surveillance, Epidemiology, and End Results (SEER) Investigation of Prognosis, Tumor Characteristics, and Predictors of Radiation Therapy

Abstract

Medulloblastoma and supratentorial PNET predominantly occur in children. Variations in histology, location, prognosis, and radiation treatment (RT) by age are poorly understood. Additionally, a significant portion of patients >3 years (y) do not undergo RT, and we attempted to determine factors associated with this treatment strategy. Using the SEER 1973-2008 database, we identified 2999 CNS supratentorial PNET/pineoblastomas (14.7%) and medulloblastomas (85.3%). Multivariate analysis (covariates: age, sex, tumor site, stage, histology, extent of surgery, RT, and diagnosis year) with Cox proportional hazards and logistic regression identified predictors of survival and radiation treatment, respectively. Median follow-up was 45 months (range 1-428). At diagnosis, age distributions were <3 (N=490), 3-17 (N=1560), 18-34 (N=604), 35-64 (N=315), and ≥65y (N=30). For ≥65 vs. <18y, there were more pineoblastomas (33.3% vs. 4.4%), supratentorial tumors (60.0% vs. 12.8%), and no surgical resection (36.7% vs. 4.8%); all P<0.001. By age, RT administration was: <3 (34.8%), 3-17 (86.9%), 18-34 (85.5%), 35-64 (83.3%), and ≥65y (60.0%); P<0.001. 5y overall (OS) and disease specific survival (DSS) were 60.3% and 63.1%. Histologies with worse 5y OS were supratentorial PNET (40.1%), pineoblastomas (53.5%), and large cell medulloblastomas (53.7%). By location, 5y OS was 65.0% for infratentorial, 47.2% for supratentorial, and 48.7% for primary spinal cord lesions. When examining 5y DSS by age group, elderly patients had the lowest DSS (17.5%), followed by <3 (47.8%), 3-17 (67.5%), 18-34 (67.0%), and 35-64y (59.9%). In multivariate analysis (3-17y reference, HR=1), patients <3 (HR 1.34), 35-64 (HR 1.50), and ≥65 (HR 2.16) had worse DSS (P<0.01). 5y OS with and without RT was 64.9% and 43.8%, respectively (P<0.001). For DSS after adjustment, significant (P<0.05) disease factors associated with decreased survival were supratentorial location (HR 1.79), distant metastases (HR 1.73), PNET histology (HR 1.58) and large cell medulloblastoma (HR 2.73). Significant treatment factors for improved DSS were gross total resection (HR 0.72) and RT (HR 0.54). In multivariate analysis (3-17y reference OR=1), only age was associated with RT use, with those <3y (OR 0.08) and ≥65 (OR 0.33) less likely to receive RT at initial diagnosis (P<0.05). Characteristics underlying prognosis of supratentorial PNET and medulloblastoma differ by age. Among elderly patients there is a greater proportion of pineoblastomas, supratentorial PNETs, and less aggressive use of surgery and RT, potentially contributing to worse survival in this high-risk population.