Cancer Questions: More study needed on risks of hormonal contraceptives

  • In this Aug. 26, 2016, photo, a one-month dosage of hormonal birth control pills is displayed in Sacramento, Calif. A large Danish study, published in December in the New England Journal of Medicine, found women who use hormonal contraceptives have a 20 percent increase in their risk for breast cancer compared to women who have never used them.  AP Photo/Rich Pedroncelli

For the Gazette
Published: 1/1/2018 10:15:28 PM

A large Danish study, published in December in the New England Journal of Medicine, found women who use hormonal contraceptives have a 20 percent increase in their risk for breast cancer compared to women who have never used them. That risk increases with a woman’s age and how long she used them.

Some earlier studies involving older formulas of contraceptives had suggested possible risk, as have more recent smaller studies involving newer formulas.

What makes the Danish study significant is its scope and design. It involved some 1.8 million women, ages 15 to 49, followed over a 10-year period, and it was done to assess an association between today’s hormonal contraceptives with their lower dosages of hormones and the risk for invasive breast cancer.

It found that women who had used hormonal contraceptives for five years or more, whether they stopped or not, had a higher risk for breast cancer than those who had never used them. The study is the first to find an increased risk for breast cancer associated with progestin-only intrauterine devices.

For women over 40, the study showed a higher risk associated with increasing age and number of years on hormonal contraceptives.

The study regarded the increases in risk — one extra breast cancer for every 7,690 women using any hormonal contraception for one year — as small, but should women worry?

Let’s put this into perspective along with other breast cancer risk factors.

A 20 percent increase in risk is the same magnitude as the increase in breast cancer risk for a woman who gains 10 pounds after menopause. Compare this to a 300 percent increase in risk for a woman who has a mother or sister who had breast cancer under the age of 30. Some risk factors can be controlled while others cannot.

The findings in the study remind women that hormonal contraceptives, like postmenopausal hormones, have both risks and benefits. Women taking postmenopausal combined estrogen and progestin have an increased risk of breast cancer while women taking estrogen alone do not have an increased risk.

All these decisions should be evaluated with an individual’s health care provider, taking into consideration a woman’s age, options and other risk factors.

What about women who are breast cancer survivors?

My recommendation for them is to use non-hormonal methods of contraception.

Much was learned and questions raised more than a decade ago about benefits and risks of ingested hormones from two randomized clinical trials involving menopausal hormone therapy for women 50 to 79. It was sponsored by the National Institutes of Health as part of its 15-year Women’s Health Initiative.

In one trial women received a hormone medication containing both estrogen and progestin or a placebo. In this trial, there were one-third fewer hip and spinal fractures among women taking the combined therapy while they were taking it, as well as one-third lower risk for colorectal cancer compared to women taking the placebo.

At the same time, women taking the combined therapy for at least five years had an increased risk for breast cancer that continued for at least 11 years after they stopped.

In the other trial, women without a uterus received a hormone medication containing estrogen alone or a placebo. In this trial, there were one-third fewer hip and spinal fractures among women taking the estrogen as well as a 23 percent reduced risk of breast cancer compared to women taking the placebo. Their reduced risk continued for at least five years after stopping the therapy.

Estrogen and progesterone are naturally occurring hormones produced by the ovaries in premenopausal women and play a role in the development of sex characteristics, as well as in menstruation and pregnancy. They have also been found to play a role in the growth of some breast cancers.

While the Danish study focuses on breast cancer risk associated with today’s hormonal birth control, such contraceptives have been shown to reduce a woman’s risk for cancer of the ovaries as well as endometrial cancer.

According to government statistics, the most popular forms of contraception among women currently using contraception are the pill followed by female sterilization and then male condoms and intrauterine devices or contraceptive implants.

What this brings into focus is the need for continued research for hormonal contraceptives that do not raise a woman’s risk for breast cancer or any cancer. In fact, the ideal contraceptive would be one that a woman can take to decrease her lifetime risk of cancer.

Dr. Grace Makari-Judson is co-director, Rays of Hope Center for Breast Cancer Research Chair, Baystate Health Breast Network, Baystate Regional Cancer Program. She is one of several Baystate health professionals who contribute columns Cancer Questions which runs monthly.


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