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

Background: In this study, radiation-induced secondary cancer risks were estimated inirradiated organs following three-dimensional conformal radiation therapy (۳D-CRT) ofAcute Lymphocytic Leukemia (ALL) in children using the Biological Effects of IonizingRadiation (BEIR) VII models.Aim: The secondary cancer risks of eye lenses, thyroid, parotid, breast, and region overlyingovaries were estimated using both excess relative risk (ERR) and excess absolute risk (EAR)models as proposed by the BEIR VII committee.Methods: In the present survey, ۱۶ patients with ALL under the age of ۱۶ years in ShahidRamezanzadeh Hospital in Yazd underwent whole brain radiotherapy (WBRT) usingCOMPACT accelerator. Measurement was performed using thermoluminescent dosimeters(TLD). The risk of secondary cancer in these organs was calculated ۳, ۵, ۱۰, ۱۵, and ۲۰ yearsafter radiation therapy.Results: The mean values of organ dose in these ۱۶ female patients were ۱.۸±۰.۱, ۱.۶۵±۰.۶۱,۱.۴۷±۰.۰۴, ۰.۱±۰.۰۳, and ۱.۵۸±۰.۵۲ cGy in the eye lenses, parotid, thyroid, breast, andregion overlying ovaries, respectively and ۲.۷, ۰.۷۶, ۰.۳, and ۰.۰۰۵ cGy for eye lens, parotid,thyroid, breast, and testis of male patient, respectively. Based on the BEIR VII models, ۳years ERR was estimated to be ۸۴۰.۳۱/۹۱.۴۹, ۱۲۳۴.۶/۲۲.۶۷, ۵.۳۹, ۴۳۷.۹۱/۰.۱۷ for the eyelenses, parotid, breast, and region overlying ovaries/testis, respectively. In addition, EARs forcancer incidence were calculated ۰.۳۳, ۰.۱۱, ۰.۰۰۲, and ۰.۰۰۹ for these organs, respectively.Conclusion: Higher risk values were found for eye lenses, thyroid, parotid, breast, and ovarycancer development. By increasing the distance of the organs from the treatment radiationfield, the scattered rays decreased.

Keywords:

Secondary Cancer Risk , Out-of-Field Dose , Radiation Therapy , Thermoluminescent Dosimeter