Observed-to-expected incidence ratios of second malignant neoplasms after radiation therapy for medulloblastoma: A Surveillance, Epidemiology, and End Results analysis.

Patients with medulloblastoma are at elevated risk for SMNs in comparison with the general population. Variations in O/E for SMNs by organ systems were found for treatment modality, age at diagnosis, and time of diagnosis. The most common site, the CNS, was involved more often in younger patients and those given chemotherapy with RT.