The Pill and Breast Cancer

Bad news for women who have been using birth control pills, although you won't learn about it from the mainstream media. An International Agency for Research on Cancer (IARC) Monographs Working Group has concluded that combined estrogen-progestogen oral contraceptives and combined estrogen-progestogen menopausal therapy are carcinogenic to humans, after a thorough review of the published scientific evidence[i].

IARC is an arm of the World Health Organization with, as they say, "global reach." Involved in everything from basic research to publication of classification systems for various cancer types, the IARC classifications are the standard of care in the U.S. and elsewhere. IARC statements are accorded great authority. One can imagine that if, in the epigraph, the words "oral contraceptives" were replaced with, say, "peanut butter" or "Republican Party membership," the political posturing and shouting in the media would never stop.

But we're talking birth control pills, so the silence is deafening.

Lists of risks associated with BCPs can be found in any medical textbook: heart attacks, strokes, blood clots, and pulmonary emboli. Less lethal but still obnoxious side-effects include depression, headaches, and nausea. Liver cancer is associated with BCP use. Liver cancer is not terribly common, but neither is it rare; the National Cancer Institute estimates that it killed about 5,500 women in 2007[ii]. For comparison, cervical cancer, whose risk is also increased by BCP use, will have claimed the lives of an estimated 3,600 women in the same year. But it is breast cancer that concerns us here. Breast cancer is the second-most common form of malignancy diagnosed in U.S. women (after skin cancer), with NCI estimates of 178,000 new diagnoses and 40,000 deaths. If the amount of money poured into screening programs is any indication, breast cancer is by far the most feared, and most politically volatile, of any malignancy.

Papers have been published for decades suggesting an increased risk of breast cancer in birth control pill users. In 1996, a meta-analysis of the 54 studies in the literature, dating back to 1959, was published in Lancet. There were three principal findings: first, that current or recent users of BCPs had a "slightly increased risk of future breast cancer; second, that the cancers tended to be lower stage (hadn't spread when diagnosed); and finally, that ten years after cessation of use, risk dropped to baseline[iii]. The National Cancer Institute cites this study on its website, as well as two others. The second study is the 2002 "Woman's CARE" study, published in the New England Journal of Medicine, in which the authors concluded that BCPs conferred no increased risk, period[iv]. Finally, the NCI cites its own 2003 study, concluding that BCP use does increase risk, and the risk is highest in young women who have used the Pill within five years of the cancer diagnosis[v]. The reason for this last finding appears to be that breasts of young women, especially adolescents, are anatomically and physiologically more vulnerable to carcinogens like BCPs because they have not gone through a nine-month pregnancy. Interestingly, the NCI website does not mention the 2005 IARC/WHO statement cited at the header of this paper.

In January 2006, the New England Journal of Medicine published a review article entitled "Estrogen carcinogenesis in breast cancer"[vi]. The authors conclude, "Studies of breast cancer have consistently found an increased risk associated with ... the use of oral contraceptives"[vii]. Then, in October, 2006 Mayo Clinic Proceedings published an article that concludes, "Use of [oral contraceptives] is associated with an increased risk of premenopausal breast cancer, especially with use before first full-term pregnancy." However, an editorial in the same issue concluded, "[A]ll risks and benefits of OC use must be considered, not just the risk of breast cancer." In 2009, another study by the Fred Hutchinson Institute revealed that triple negative breast cancer (TNBC), one of the most lethal types, showed that women who start BCPs before age 18 multiply their risk of TNBC by 3.7 times, and recent users multiply their risk by 4.2 times[viii]. Yet Louise Brinton, one of the co-authors of this and numerous other studies demonstrating increased rates of breast cancer in young women taking oral contraceptives, is a researcher at the NCI and chief organizer of a 2003 symposium on breast cancer and reproductive events in young women that failed to mention this connection.

Which brings us to the crux of the issue. There is evidence that birth control pills, especially when used by young women, increase a woman's risk of breast cancer[ix]. Given that we're talking about the most widely used class of drugs on the planet, and one of the commonest forms of malignancy in women, the implications are not trivial. But the spin of the medical establishment, as well as cancer charities including the National Cancer Institute, American Cancer Society, and Susan Komen Foundation, is to push these findings under the rug.

Is it because our entire culture is organized around contraception and its twisted sister, abortion? Justice Sandra Day O'Connor recognized the central position of contraception (and abortion) to our way of life fifteen years ago when she said, "For two decades, people have organized intimate relationships ... in reliance on the availability of abortion in the event that contraception should fail"[x].

Taking away BCPs would be like taking away air. And yet, I think there are people out there who would like to know of this information. To borrow phrasing from the homepage of the Coalition on Abortion/Breast Cancer, not all women with breast cancer used birth control pills, and not all women who have used birth control pills will develop breast cancer. But BCP use appears to be a risk factor -- an avoidable risk factor -- in the development of breast cancer, and I think that's worth knowing[xi].

[i] International Agency for Research on Cancer (IARC), World Health Organization (WHO), Press Release No. 167, 29 July 2005. Available at

[ii] To be clear, it is a specific subtype -- hepatocellular carcinoma (HCC) -- which is linked with BCP use. But the vast majority of "liver and bile duct cancer" in the NCI data is HCC. Not all HCC is linked to BCP use. In fact, most is not: Twice as many men as women die of HCC. But BCP use does increase HCC risk in women. Also, HCC is not to be confused with hepatic adenoma, a benign liver tumor associated with BCP use.  

[iii] Collaborative Group on Hormonal Factors in Breast Cancer. Breast cancer and hormonal contraceptives: Collaborative reanalysis of individual data on 53,297 women with breast cancer and 100,239 women without breast cancer from 54 epidemiological studies. Lancet 1996; 347:1713-1727.

[iv] Marchbanks PA, McDonald JA, Wilson HG, et al. Oral Contraceptives and the risk of breast cancer. New England Journal of Medicine 2002; 346(26):2025-2032.

[v] Althuis MD, Brogan DD, Coates RJ, et al. Breast cancers among very young premenopausal women (United States). Cancer Causes and Control 2003; 14(2):151-160.

[vi] Yager JD, Davidson, NE. Estrogen Carcinogenesis in Breast Cancer. New England Journal of Medicine 2006; 354:270-282.

[vii] ibid, "Conclusions." My emphasis.

[viii] Dolle J, Daling J, White E, Brinton L, Doody D, et al. Risk factors for triple-negative breast cancer in women under the age of 45 years. Cancer Epidemiol Biomarkers Prev 2009;18(4)1157-1166

[ix] Similar data exist regarding abortion as a risk factor for breast cancer, but that is beyond the scope of this little piece.

[x] U.S. Supreme Court Planned Parenthood of Southeastern PA v. Casey, 505 U.S. 833 (1992) Quote is from Sec. III A 2 para. 3 Entire case is available at FindLaw, under "Cases and Codes," U.S. Supreme Court.

[xi] I would like to thank Dr. Mary Davenport for her suggestions and additional citations.
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