A recent study in the New England Journal of Medicine shed some light on the link between chemotherapy and loss of ovarian function. The treatment of cancers, while lifesaving, can cause infertility in both men and women. Cancer therapy reduces fertility by affecting the ovaries. Chemotherapy and radiation can deplete the number of immature eggs, called follicles, and cause ovaries to lose hormone secretion. The type of therapy and the age of a woman can both affect susceptibility to infertility. For example, alkylating chemotherapeutic agents are potent inhibitors of fertility because they attack both dividing and non-dividing cells in the ovaries.
The study by Sandra M. Swain, M.D. et al. investigated the effectiveness of a chemotherapy regimen for breast cancer and found that successful treatment correlated with a loss of menstruation, called amenorrhea. In the study, amenorrhea was classified as loss of menstruation for at least 6 months in the two years following chemotherapy. In these patients, amenorrhea correlated with increased survival eight years after treatment and decreased disease remission.
Why might successful cancer treatments also cause amenorrhea? One possibility is that reduction in ovarian function, which produces estrogen, may prevent cancers from expanding. Breast cancers can be divided into two types-those with and without estrogen receptors. Estrogen released from the ovaries stimulates estrogen receptor-positive cancers to grow and, thus, damage to the ovaries may prevent growth. Interestingly, the study found that the link between amenorrhea and survival occurred in women with both estrogen receptor-positive and –negative cancers. This indicates that estrogen may not cause increased survival rates in women with loss of menstruation. Instead, decreased ovarian function may inhibit tumor progression in other ways. One final possibility is that ovarian failure may simply be a byproduct of successful cancer therapy.
In the future, the link between amenorrhea and survival may be used to develop tests of molecular indicators, called biomarkers. The biomarkers could be used during cancer treatment to signal when a therapy had reached success, rather than waiting for amenorrhea to occur. Further work is also needed to determine the cause of treatment-induced amenorrhea and examine ways to prevent the loss of fertility from such therapies.