Treatments used to induce ovulation appear to increase the overall risk of cancer, the results of a study published in the American Journal of Epidemiology suggest.

“Ovulation-inducing drugs are widely used for ovarian follicle stimulation, either as independent therapies or during in vitro fertilization cycles,” Dr. Ronit Calderon-Margalit, of Hadassah-Hebrew University, Jerusalem, Israel, and colleagues explain. “The scientific literature provides inconsistent information on the association between ovulation induction treatment and cancer incidence.”

To investigate further, the researchers examined data from 15,030 women enrolled in the Jerusalem Perinatal Study who gave birth between 1974 and 1976 and then participated in a postpartum survey. The women were linked with the Israel Cancer Registry to obtain information on the number of cancers diagnosed through 2004.

A total of 1,215 women developed cancer. The 567 women who received drug treatment to induce ovulation had a 36-percent increased risk of developing cancer at any site.

Treatment with ovulation-inducing drugs was not associated with ovarian cancer, but increased the risk of breast cancer by 42 percent; uterine cancer risk by more than 3-fold, and the risk of non-Hodgkin lymphoma by about 2.5-fold.

Treatment with the ovulation-inducing drug clomiphene specifically was associated with 4.6-times the risk of uterine cancer and 2.6-times the risk of malignant melanoma.

“The potential implications of this study relate firstly to the need of further research and better registries of fertility treatments,” Calderon-Margalit commented to Reuters Health.

“I believe that fertility treatments will continue, but if our findings will be confirmed by others, women who are treated with clomiphene, and perhaps other ovulation induction agents, will need screening for uterine cancer,” she added. Future research will potentially explain the role of hormones in the development of cancers such as malignant melanoma and non-Hodgkin lymphoma.

SOURCE: American Journal of Epidemiology, February 1, 2009.