Gonads Exposure to Scattered Radiationand Associated Second Cancer Risk From Pelvic Radiotherapy

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.