What is the risk of infertility after treatment with chemotherapy and/or radiation therapy?
Both chemotherapy and radiation therapy are toxic to the gonads: ovaries in women, testicles in men. In women, damage to the ovaries can result in ovarian failure (premature menopause) with infertility and symptoms related to low estrogen levels (hot flashes, night sweats, mood changes, etc.) In men, damage to the testicles is likely to result in diminished sperm production but hormone production is less likely to be impaired. Therefore, sexual function may continue normally in spite of decrease or absent sperm production.
The effects of treatment depend on the specific chemotherapy used, the total dose and the age at the time of treatment.
What effect does age have?
In general, the gonads of boys and girls are relatively resistant to the effects of chemotherapy before the onset of puberty. Both boys and girls may go through a normal puberty and have normal reproductive function for a while, in spite of treatment during childhood or early adolescence. In girls, there is a risk of early menopause in the 20s or 30s. Radiation therapy to the pelvis or abdomen in boys or girls may cause enough damage to the gonads so that puberty does not occur normally.
After puberty, sperm production is very sensitive to chemotherapy and radiation. Radiation to the pelvis or directly to the testicles will stop sperm production. Radiation to the upper leg or upper abdomen may cause some damage to the testicles, but sperm production may recover in these cases. Radiation therapy related to bone marrow transplantation usually causes infertility, but this has been reversible in a few cases with recovery of sperm production up to seven years later.
In girls, the ovaries are very sensitive to chemotherapy and radiation after puberty and even more so as they get older. Women are born with all the eggs they will ever have. Women who are younger - less than 25 years old - may withstand the effects of chemotherapy because their ovaries contain so many more eggs than older women. Even if their reproductive function seems to be intact after treatment (periods continue normally), they have a risk of early menopause.
What are the effects of dose and type of chemotherapy?
Some particular types of chemotherapy are known to be particularly toxic to the gonads. Alkylating agents, for example cytoxan (cyclophosphamide), is particularly damaging to both ovaries and testicles. Even low dose cytoxan given over a long period of time (ex. for treatment of systemic lupus, rheumatoid arthritis, or kidney disorders) can have a detrimental effect. Others, like methotrexate, seem to be relatively safer. Current cancer treatment protocols often contain many medications given in overlapping or alternating regimens. Very little is known about the long term effects of these newer regimens, but they are likely to cause damage to the gonads.