Gonads Exposure to Scattered Radiation and Associated Second Cancer Risk from Pelvic Radiotherapy

Purpose: The purpose of this study was to evaluate the risk of gonad cancer induction in adults with pelvic cancer (bladder, rectum, endometriosis) after radiation therapy. Materials and Methods: In two fractions of radiotherapy, Thermo Luminescence Dosimeters (TLDs) measured the peripheral dose to the testis and ovary. With 3D planning, all patients received a 45 Gy total dose in four fields in the prone position. Researchers investigated the doses produced by linear accelerators operating at 18 MeV. Results: The mean Excess Relative Risk (ERR) was measured based on the BEIR IIV models. Right pelvic radiotherapy of men was 0.795 ± 0.168 and 0.675 ± 0.134, and for women was 1.015 ± 0.561 and 0.884 ± 0.468 after 5 and 10 years of treatment, respectively. Left pelvic radiotherapy was 0.855 ± 0.172, 0.725 ± 0.138 for men and 0.880 ± 0.464, 0.722 ± 0.342 for women respectively (95% confidence interval). These values for women were higher (p < 0.05). Conclusion: Estimating the second cancer risk of untargeted organs is crucial in radiotherapy. The out-of-field doses can be minimized by using a linear accelerator with a single energy mode and proper shields.