Thyroid Dysfunction as a Late Effect in Survivors of Pediatric Medulloblastoma/Primitive Neuroectodermal Tumors A Comparison of Hyperfractionated versus Conventional Radiotherapy

BACKGROUND. Primary hypothyroidism is a common sequela of craniospinal radiotherapy in the treatment of pediatric brain tumors. METHODS. The authors compared the incidence of primary hypothyroidism after hyperfractionated radiotherapy (HFRT) (n = 14 patients) versus conventionally fractionated radiotherapy (CRT) (n = 34 patients) in a group of pediatric patients with medulloblastoma/primitive neuroectodermal tumors (MB/PNET). RESULTS. The mean age at the time of tumor diagnosis was 7.9 years in the HFRT group and 8.4 years in the CRT group. The patients were followed for a mean of 4.6 years (HFRT) and 8.3 years (CRT) after diagnosis. Mean radiation doses to the thyroid were similar in both radiotherapy groups (29 gray [Gy] [HFRT] vs. 24 Gy [CRT]). Approximately 14% of the HFRT and 62% of the CRT patients developed primary hypothyroidism within a similar period after irradiation (3.2 years [HFRT] vs. 3.0 years [CRT]). Analysis by cumulative incidence function demonstrated a significant difference in the risk of developing thyroid dysfunction between these two groups of patients (P = 0.02). CONCLUSIONS. The current study findings suggest that the use of HFRT in the treatment of pediatric patients with MB/PNET is associated with a lower risk of these patients developing primary hypothyroidism.