Radiation safety of receptive anal intercourse with prostate cancer patients treated with low-dose-rate brachytherapy

Abstract

PurposeProstate low-dose-rate (LDR) brachytherapy involves implantation of radioactive seeds permanently into the prostate gland. During receptive anal intercourse, the penis of the partner may come in close proximity to the implanted prostate gland. We estimate the potential intrarectal dose rates and suggest guidance on radiation precautions. Methods and MaterialsOne hundred two patients were included in the study. After implantation, with patients under anesthesia in the dorsal lithotomy position, a new set of ultrasound (US) images and a CT scan were obtained. The images were fused, radioactive seeds and US probe locations were determined on the CT, and prostate, bladder, and rectal contours were drawn on the US. Dose rates (cGy/h) were calculated for the portion of the US probe spanning the prostate for several dose-volume histogram parameters. ResultsTwenty patients were treated with 125I and 82 patients with 103Pd. Average dose rates at Day 0 to the portion of the US probe spanning the prostate were 2.1 ± 1.3 cGy/h and 2.5 ± 0.8 cGy/h for patients treated with 125I and 103Pd, respectively. After 60 days, average calculated probe dose drops to 1.0 ± 0.6 cGy/h and 0.2 ± 0.1 cGy/h for 125I and 103Pd, respectively. ConclusionsDuring the immediate weeks after prostate seed implant, the estimated intrarectal dose rates are higher in 103Pd compared to 125I. As 103Pd decays faster than 125I, 2 months after the implant, radiation exposure from 103Pd becomes lower than 125I. Receptive anal intercourse time should be kept as low as possible during 2 and 6 months after low-dose-rate brachytherapy of the prostate with 103Pd and 125I, respectively.