Reduced interest in sex (low libido) is common during treatment for prostate cancer. Quite often it occurs due to anxiety and fatigue rather than the treatment itself. However, libido can also be affected by ADT, which lowers testosterone levels, and by the sexual side effects associated with radiation therapy or surgery.
Most men notice that their sex drive returns when treatment ends, but for some men, the problem is ongoing. Adjusting to changes in sex drive can be emotionally and physically challenging for men and their partners. See Restoring your sex life for tips to help with this issue.