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Do Oral Contraceptives Cause Breast Cancer? The Answer Is Finally In!

Tens of millions of women have taken oral contraceptives over the last few decades. Did they increase their risk for breast cancer? Read the new research.
Do Oral Contraceptives Cause Breast Cancer? The Answer Is Fi...

The New England Journal of Medicine (Dec. 7, 2017) has answered a long-simmering controversy about hormonally-based contraception. In a nutshell, birth control pills do raise the risk of breast cancer. Hormonal implants and IUDs that rely on hormonal release were also implicated. Lest you think this is new news, let us share what we wrote about oral contraceptives and breast cancer more than 40 years ago in the first edition of The People’s Pharmacy:

Step Into The People’s Pharmacy Time Machine:

The original edition of The People’s Pharmacy was published in 1976 (St. Martin’s Press). Chapter 9 was all about Contraception: The Pill, the IUD, and Vasectomy:

“So, you don’t want to make a baby. What you do want is a simple, safe, and effective means of contraception. You have heard an awful lot about the side effects of birth control pills, but what is myth and what is real?

“Oral contraceptives have been available in this country since 1960. This form of birth control represented a revolutionary breakthrough for effective family planning. Today, well over eight million American women use the Pill, because it works and because it is essentially hassle-free. Nevertheless, a cloud of controversy has followed this drug ever since it was introduced.”

“…Okay, let’s fact it, thrombophlebitis, pulmonary embolism and stroke are some of the risks associated with The Pill. But just as millions gamble on the relationship between cigarette smoking and cancer, millions are willing to gamble that the Pill won’t thus affect them. What about cancer, however? Do oral contraceptives increase a woman’s likelihood of developing this dread disease? Reports in the press have been contradictory. Some say the Pill reduces the incidence of cancer, while others claim that it magnifies the risk. Well, what is the truth?

“Unfortunately, as is the case with almost everything in medical science, there is no one Truth. Whenever you deal with a controversial issue, especially one as volatile as that of the Pill, there are bound to be conflicting research accounts…

“Most of the attention has been directed to the problem of breast cancer. This is certainly understandable since it is such a common and dangerous form of cancer…Many investigators have reported unequivocally that oral contraceptives do not lead to an increase in the number of cases of breast cancer, and some doctors have even reported that women who use the Pill are less likely to come down with this disease (BMJ, Sept. 23, 1972). Dr. Martin Vessey and his colleagues concluded 45 years ago:

“The data do not suggest that the use of oral contraceptives is related in any way to the risk of breast cancer but provide some evidence that the preparations may actually protect against benign breast disease. This protective effect is largely confined to women who continue to use oral contraceptives and have used them altogether for more than two years. Such women appear to have only about 25% as great a risk of being admitted to hospital for a breast biopsy as women who have never used oral contraceptives at all.”

An article titled “Effects of Estrogenic Therapy on the Breast” published in the Southern Medical Journal (July, 1971) noted:

“Certain observers through the years have believed that breast cancer may be caused by estrogenic therapy…Actually, very little substantive data are available to prove any relationship in the human. Sporadic case reports of patients who develop breast cancer after estrogenic therapy have appeared in the literature. Wilson, in 1966, indicated a lessened occurrence of breast cancer in women receiving estrogens.”

We went on to warn that many other studies did report an association between oral contraceptives and breast cancer. In 1976 we cautioned about a connection between the Pill and blood clots, breast and uterine cancer (endometrial carcinoma).

Fast Forward to December 7, 2017:

The New England Journal of Medicine published a study involving 1.8 million Danish women. They were tracked “on average for 10.9 years (a total of 19.6 million person-years.” Over that time, “11,517 cases of breast cancer occurred.” The authors noted a disturbing trend. Women who used hormonal contraception for less than a year had a 9% increased risk of developing breast cancer. Women who used such contraception more than 10 years had a 38 percent relative risk of developing breast cancer. Overall, when the researchers compared current and recent users of hormonal contraception, the risk was 20% greater in women who used such products compared to women who never used hormonal contraception.

Relative vs. Absolute Risk:

Trying to put this sort of study into perspective is always challenging. First, it is important to recognize that breast cancer was relatively uncommon. Of the 1.8 million women followed over a decade, there were a total of 11,517 cases of breast cancer. The authors note:

“The overall absolute increase in breast cancers diagnosed among current and recent users of any hormonal contraceptive was 13 per 100,000 person-years, or approximately 1 extra breast cancer for every 7690 women using hormonal contraception for 1 year. Conclusions: The risk of breast cancer was higher among women who currently or recently used contemporary hormonal contraceptives than among women who had never used hormonal contraceptives, and this risk increased with longer durations of use; however, absolute increases in risk were small.”

The People’s Pharmacy Perspective:

Many health professionals have long accepted the idea that hormones like estrogen and progestin increase the risk of breast cancer. But there was a belief that modern-day oral contraceptives posed little, if any, risk. That’s because the formulations that are now prescribed contain far lower hormonal amounts than products from the 1970s and 1980s.

Roni Caryn Rabin, writing in the New York Times, quoted oncologist Dr. Marisa Weiss:

“Gynecologists just assumed that a lower dose of hormone meant a lower risk of cancer. But the same elevated risk is there.

“It’s small but it’s measurable, and if you add up all the millions of women taking the pill, it is a significant public health concern.”

An editorial in the New England Journal of Medicine (Dec. 7, 2017) points out that “The association between the current use of oral contraceptives and breast cancer is well established.” The 20 percent increased relative risk has been shown in other large studies. It has not changed substantially between higher-dose hormonal contraception of the 1970s and 1980s and the lower-doses used today. There was also a hint that a risk may persist for several years after the hormones are stopped.

The editorialist goes on to write:

“…these data suggest that the search for an oral contraceptive that does not elevate the risk of breast cancer needs to continue. In the 1980s and 1990s, there was some optimism regarding the development of a formulation that would reduce a woman’s risk of breast cancer, but research into this possibility appears to have stalled.”

Mad As Hell!

We’re mad as hell. What about you? Tens of millions of women have been exposed to oral contraceptives and other hormonal birth control products over the last 50 years. Scientists have known for most of that time that there could be a risk of breast cancer associated with these formulations. As long ago as the 1980s researchers were beginning to develop products that would not pose such a risk and might even lower it. But that work “stalled.” It is way past time to develop safer contraceptives.

The risk of breast cancer caused by hormonal contraception is repeatedly described as “small.” That is little consolation to the women who develop breast cancer because of hormonal birth control. For them it is 100%.

It is estimated that 10 million women currently rely on oral contraceptives. Based on the new data one might expect roughly 1,300 cases of breast cancer each year brought on by exposure to oral contraceptives. We think that is 1,300 too many!

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.” .
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