Do Hormonal Contraceptives Increase Breast Cancer Risk?

Andrew M. Kaunitz, MD


December 22, 2017

Hello. I am Andrew Kaunitz, professor and associate chair in the Department of Obstetrics and Gynecology at the University of Florida College of Medicine in Jacksonville.

Today I'd like to discuss hormonal contraception and risk for breast cancer.

Many women wonder whether use of hormonal contraception might increase their risk of being diagnosed with breast cancer. A recent report in the New England Journal of Medicine[1] used Danish national databases to determine the association between use of hormonal contraception and risk for invasive breast cancer in women aged 15-49 years.

Some 1.8 million women were followed from 1995 to 2012. Among these women, more than 11,000 breast cancers were diagnosed.

Birth control pills represented the most common hormonal contraceptives used, with the second most common method being the progestin intrauterine device (IUD).

Compared with women who had never used hormonal contraceptives, the relative risk for breast cancer in current or recent users was 1.20. Current or recent use of the progestin-releasing IUD was associated with a similar small elevated risk. Both of these relative risks achieved statistical significance.

Unfortunately, several shortcomings reduce the credibility of this Danish study's findings. The investigators used a database which includes women age 15-49 years. However, more than three quarters of invasive breast cancers are diagnosed in women older than age 49.[2] Accordingly, it was surprising that the authors chose to limit their analysis to younger women.

Screening mammograms and clinical breast exams strongly contribute to the diagnosis of breast cancer; therefore, I was also surprised that the authors did not adjust their findings for these two items.

Finally, epidemiologists caution that in cohort studies, odds ratios of less than 2 should not be interpreted as suggesting causation.[3] It is therefore puzzling that the investigators failed to acknowledge this major limitation of their findings.

A National Institutes of Health–funded case-control study performed by the Centers for Disease Control and Prevention, which many consider to be definitive with respect to this topic, found no suggestion of an elevated risk for breast cancer with use of oral contraceptives.[4]

The findings of this Danish study will not change how I counsel women regarding benefits and risks of hormonal contraception.

Thank you for the honor of your time. I am Andrew Kaunitz.


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