Infertility is the inability to start or maintain a pregnancy. For men, infertility occurs when the testes stop producing sperm cells. For women, infertility occurs when the ovaries cannot produce oocytes (mature eggs) for ovulation, or if other damage to the reproductive system prevents an embryo from successfully being fertilized or implanting and growing in the uterus.
Chemotherapy kills rapidly dividing cells throughout the body. Infertility is a potential side effect, as damage to sperm and egg producing cells often occurs. Chemotherapy drugs vary in toxicity. In general, the more courses of chemotherapy, the more damage is likely.
Radiation Therapy also kills rapidly dividing cells, but only in or around its target area. If the radiation field includes the brain or is aimed close to or at the pelvic areas of the body it may cause infertility by damaging areas that control hormone production or by direct damage to the testes or ovaries.