Risk of Hypogonadism From Scatter Radiation During Pelvic Radiation in Male Patients With Rectal Cancer

Purpose: Recent studies have reported fluctuations in sex hormones during pelvic irradiation. The objective of this study was to observe the effects of radiation on hormonal profiles for two treatment modalities: conventional external beam radiotherapy (EBRT) and high-dose-rate brachytherapy (HDRBT) given neoadjuvantly for patients with rectal cancer. Methods and Materials: Routine serum follicle stimulating hormone (FSH), luteinizing hormone (LH), and testosterone levels were collected from 119 consecutive male patients receiving either EBRT, using 45.0-50.4 Gy in 25-28 fractions with concurrent 5-fluorouracil chemotherapy or HDRBT using 26 Gy in 4 fractions. Results: Thirty patients with initially abnormal profiles were excluded. Profiles included in this study were collected from 51 patients treated with EBRT and 38 patients treated with HDRBT, all of whom had normal hormonal profiles before treatment. Mean follow-up times were 17 months for the entire patient cohort-14 and 20 months, respectively-for the EBRT and HDRBT arms. Dosimetry results revealed a mean cumulative testicular dose of 1.24 Gy received in EBRT patients compared with 0.27 Gy in the HDRBT group. After treatment, FSH and LH were elevated in all patients but were more pronounced in the EBRT group. The testosterone-to-LH ratio was significantly lower (p = 0.0036) in EBRT patients for tumors in the lower third of the rectum. The 2-year hypogonadism rate observed was 2.6% for HDRBT compared with 17.6% for EBRT (p = 0.09) for tumors in the lower two thirds of the rectum. Conclusion: HDRBT allows better hormonal sparing than EBRT during neoadjuvant treatment of patients with rectal cancer.