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 hyperf ractionated radiotherapy (HFRT) (n = 14 patients) versus conventionall y fractionated radiotherapy (CRT) (n = 34 patients) in a group of pedi atric 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 r adiotherapy groups (29 gray [Gy] [HFRT] vs. 24 Gy [CRT]). Approximatel y 14% of the HFRT and 62% of the CRT patients developed primary hypoth yroidism within a similar period after irradiation (3.2 years [HFRT] v s. 3.0 years [CRT]). Analysis by cumulative incidence function demonst rated a significant difference in the risk of developing thyroid dysfu nction between these two groups of patients (P = 0.02). CONCLUSIONS. T he current study findings suggest that the use of HFRT in the treatmen t of pediatric patients with MB/PNET is associated with a lower risk o f these patients developing primary hypothyroidism. (C) 1997 American Cancer Society.