Impact of Scattered Radiation on Testosterone Deficiency and Male Hypogonadism in Rectal Cancer Treated with External Beam Pelvic Irradiation

Background: We performed a prospective study to evaluate the effects of pelvic irradiation on FSH, LH and testosterone levels in male patients with rectal adenocarcinoma. Our aim was to compare the level of male sex hormones in peripheral blood serum before and after pelvic irradiation.Methods: The eligible participants were ۴۰ men with rectal adenocarcinoma who underwent pelvic radiotherapy as part of their treatment for primary tumor, either before or after surgery. All patients received a ۵۰-Gy radiation dose to the pelvis, ۲ Gy per fraction, five days per week. Blood was sampled three times during the study: once before radiation, at the end of the radiation course and ۴ to ۶ weeks after radiotherapy.Results: Median age of the patients was ۵۸ years (range ۱۸-۸۲). The mean testis dose of radiation per fraction in all ۴۰ patients was ۱۶.۳ cGy with a standard deviation of ۱۵.۲۲ (range ۵.۵-۶۴.۸). Serum levels of FSH revealed a significant increase from ۷.۵ ± ۱.۷ IU/L (before treatment) to ۲۰.۹ ± ۱۷.۸ IU/L [end of radiotherapy (P<۰.۰۰۱)] and ۲۴.۱ ± ۲۰.۵ IU/L [۴ to ۶ weeks after radiotherapy (P<۰.۰۰۱)]. Serum LH levels were significantly elevated from ۸.۰۴ ± ۱.۲ IU/L before radiation to ۱۱.۶ ± ۱۱.۵ IU/L at the end of radiotherapy (P<۰.۰۰۱) and ۱۲.۵ ± ۹.۹ IU/L ۴ to ۶ weeks after the final course of radiotherapy (P<۰.۰۰۱). There was a decrease in serum testosterone from ۵.۳±۲.۱ ng/mL before radiation to ۴.۲ ± ۱.۹ ng/mL at the end of radiotherapy (P=۰.۰۰۴) and ۴.۵ ± ۲ ng/mL ۴ to ۶ weeks after radiotherapy (P=۰.۰۳۵). No significant correlation was seen between age and differences in sex hormones (LH, P=۰.۶۰۵; FSH, P=۰.۳۸۰; testosterone, P=۰.۱۶۱).Conclusion: There was a significant change in serum levels of male sex hormones after pelvic irradiation for rectal cancer (total dose, ۵۰ Gy) that indicates considerable testicular damage under these circumstances. Thus, it seems logical to use techniques that reduce the radiation dose to the testicles and to consider the benefits of hormone replacement therapy as well as semen cryopreservation for high-risk patients who desire children in the future.