Estimation of Secondary Cancer Risk of Radiosensitive Organs for Leukemia from Head Radiotherapy in Pediatric Patients

The scattered radiation from the treatment volume might be more significant for children than for adults because of life expectancy. The present study used biological effects of ionizing radiation (BEIR) VII models to estimate radiation-induced secondary cancer risks in irradiated organs following three-dimensional conformal radiation therapy (3D-CRT) of Acute Lymphocytic Leukemia (ALL) in children. Both excess absolute risk (EAR) and excess relative risk (ERR) models were used to estimate the secondary cancer risks of eye lenses, thyroid, parotid, breast, and region overlying ovaries.

In this expository cross-sectional study, from 45 patients who were examined, 16 patients age under 18 years (mean age of 9.6) met the criteria for entering the study in Shahid Ramezanzadeh Hospital in Yazd underwent whole brain radiotherapy (WBRT) using COMPACT accelerator. Measurement was performed using thermoluminescent dosimeters (TLD). After radiation therapy, the secondary cancer risk in these organs was calculated.

The organ dose mean values in female patients were 1.8±0.1, 1.65±0.61, 1.47±0.04, 0.1±0.03, and 1.58±0.52 cGy in the eye lenses, parotid, thyroid, breast, and region overlying ovaries, respectively and 2.7±0.6, 0.76±0.17, 0.6±0.05, and 0.005±0.002 cGy for eye lens, parotid, thyroid, breast, and testis of male patient, respectively. The ERR and EAR were estimated after 3, 5, 10, 15 and 20 years for eye lens, parotid breast, and ovary/testis for female/male.

Higher risk values were found for eye lenses and thyroid. The scattered rays decreased by increasing the organ distance from the treatment radiation field.