Side effects of brachytherapy can include swelling, bruising, bleeding, or pain and discomfort at the spot where the radiation was delivered. Brachytherapy used for gynecologic cancers or prostate cancer can lead to short-term urinary symptoms, including incontinence or pain on urination. Brachytherapy for these cancers can also lead to diarrhea, constipation and some rectal bleeding. Prostate brachytherapy can occasionally cause erectile dysfunction.