Risk of subsequent cancer following a primary CNS tumor.

Improvements in survival among central nervous system (CNS) tumor patients has made the risk of developing a subsequent cancer an important survivorship issue. Such a risk is likely influenced by histological and treatment differences between CNS tumors. De-identified data for 41,159 patients with a primary CNS tumor diagnosis from 9 Surveillance, Epidemiology and End Results (SEER) registries were used to calculate potential risk for subsequent cancer development. Relative risk (RR) and 95 % confidence interval (CI) of subsequent cancer was calculated using SEER*Stat 7.0.9, comparing observed number of subsequent cancers versus expected in the general United States population. For all CNS tumors studied, there were 830 subsequent cancers with a RR of 1.26 (95 % CI, 1.18-1.35). Subsequent cancers were observed in the CNS, digestive system, bones/joints, soft tissue, thyroid and leukemia. Radiotherapy was associated with an elevated risk, particularly in patients diagnosed with a medulloblastoma/primitive neuroectodermal tumor (MPNET). MPNET patients who received radiotherapy were at a significant risk for development of cancers of the digestive system, leukemia, bone/joint and cranial nerves. Glioblastoma multiforme patients who received radiotherapy were at lower risks for female breast and prostate cancers, though at an elevated risk for cancers of the thyroid and brain. Radiotherapy is associated with subsequent cancer development, particularly for sites within the field of radiation, though host susceptibility and post-treatment status underlie this risk. Variation in subsequent cancer risk among different CNS tumor histological subtypes indicate a complex interplay between risk factors in subsequent cancer development.