The risk of secondary cancer in pediatric medulloblastoma patients due to three-dimensional conformal radiotherapy and intensity-modulated radiotherapy.

BACKGROUND: Craniospinal irradiation (CSI) is the standard radiation therapy treatment for medulloblastoma. The aim of this study was to estimate and compare the lifetime risk of radiation-induced secondary cancer in pediatric medulloblastoma patients using three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT).

MATERIALS AND METHODS: 3D-CRT and IMRT plans were performed for 10 CSI pediatric patients. The average absorbed doses for organs at risk (OARs) was calculated from dose-volume histograms on the treatment planning system. The average lifetime risk of radiation-induced secondary cancer was then calculated.

RESULTS: Lifetime risk of secondary cancer for CSI pediatric patients treated using IMRT decreases in some OARs compared with those treated using 3D-CRT. This is attributable to the decrease in the average absorbed dose in some OARs when using IMRT technique.

CONCLUSION: Follow-up of medulloblastoma pediatric patients should be performed after ending the treatment course in order to diagnose early secondary tumors. IMRT technique is substantially better than 3D-CRT in terms of lifetime risk of radiation-induced secondary cancer, probably due to reduced dose to OARs especially to the thyroid, which is the most sensitive organ to radiation.