Fertility Meds Didn't Cause Breast Cancer

Breast cancer was not long term effect of fertility medications

(RxWiki News) Not all of the long-term impacts of fertility treatment are clear. But researchers have found reassuring evidence for those hoping to have a baby using such treatments.

A new three-decade study found no clear link between fertility treatments and increased risk of breast cancer in women.

The researchers want to continue to study the long-term effects of fertility treatments designed to improve a woman’s chances of becoming pregnant.

"Talk with your doctor about the potential effects of fertility treatments."

Louise A. Brinton, PhD, MPH, chief of the Hormonal and Reproductive Epidemiology Branch of the National Cancer Institute in Bethesda, Maryland, led this research.

Dr. Brinton and colleagues sampled data from a study group of more than 12,000 women to examine the long-term relationship between the use of fertility medications and breast cancer risk.

The initial participants were evaluated for infertility between 1965 and 1998 and were followed until 2010. Of the 9,892 women in the original group, 749 had developed breast cancer.

Dr. Brinton’s team obtained medical documents for 696 of the 749 women who developed breast cancer. Of those women, 536 were confirmed to have had invasive breast cancer.

Breast cancer is considered invasive when it starts to grow into healthy tissue.

"Overall, our data show that use of fertility drugs does not increase breast cancer risk in this population of women, which is reassuring,” Dr. Brinton said.

Focusing on two particular prescription fertility treatments, the study looked at women who took clomiphene citrate (brand name Clomid) and gonadotropins, another type of fertility treatment.

This study showed that women who took those fertility medications did not have an increased risk for breast cancer compared to women not treated with those medications.

Dr. Brinton and team did find an elevated risk for invasive breast cancer in the small group of women exposed to 12 or more cycles of clomiphene, which is more than double the normal dosage. That group was 1.5 times more likely to develop breast cancer compared to women who never took fertility medications.

These researchers also found that women who received fertility treatments but were unable to become pregnant were twice as likely to develop breast cancer when compared to women who did not receive fertility treatments.

"The observed increase in risk for these small subsets of women may be related to persistent infertility rather than an effect of the medications," Dr. Brinton said in a press statement. "Nevertheless, these findings stress the importance of continued monitoring of women who are exposed to fertility drugs."

The study participants who developed breast cancer had an average age of 53.

"This cohort of women should continue to be monitored as they progress into a typical breast cancer age range,” Dr. Brinton said.

“In addition, data are needed to assess the long-term effects of fertility drugs given in current practice,” she said.

This study was published in the April issue of Cancer Epidemiology, Biomarkers and Prevention, a journal for the American Association of Cancer Research.

Funding was provided by the National Cancer Institute, a part of the federal National Institutes for Health.

Dr. Brinton did not report any relevant conflicts of interest.

Review Date: 
April 7, 2014