A Dirty Little Secret

Below is a letter written by Dr. Chris Kahlenborn on the 50^th anniversary of the birth control pill. Dr. Kahlenborn practices internal medicine in Altoona, Pennsylvania. He co-authored “Oral Contraceptive Use as a Risk Factor for Pre-menopausal Breast Cancer:  A Meta-analysis” (2006)

The Pill After 50 Years: The Dirty Little Secret

By Chris Kahlenborn M.D.

I find it disturbing that after nearly 50 years, both the media and the medical establishment have failed to give a true airing to one of the pill’s most dangerous side effects, namely, that “dirty little secret.”   What’s that? One need only check the Mayo Clinic Proceedings—the major medical publication of the Mayo Clinic—to find our little-known study, which showed that the pill increases the risk of premenopausal breast cancer substantially when taken at a young age (see Mayo Clinic Proceedings: October 3, 2006). In October 2006, we reviewed the medical literature and combined data in an analysis (referred to as a meta-analysis): We found that 21 out of 23 studies showed that using oral contraceptives prior to a woman’s first birth resulted in a 44 percent increased risk in premenopausal breast cancer. Our meta-analysis remains the most recent study in this area and updates the previously analysis (the Oxford analysis published in 1996), which relied on older data with older women (two-thirds of whom were over age 45); unfortunately, the Oxford study continues to be quoted by ACOG, textbooks, the National Cancer Institute, the American Cancer Society and most researchers and obstetricians, claiming that oral contraceptives carry little breast cancer risk especially 10 years after last use.


I continue to be amazed at the discordance between the medical literature and public/medical awareness. To my dismay, after our meta-analysis was published, the Mayo Clinic sent out a press release to all major media in the country. The response? (          ).  The blank space between the parentheses is purposeful. Although our meta-analysis received scant internet coverage, almost no major media covered this study, which is shocking, given the fact that about 40,000 women in the U.S. get premenopausal breast cancer annually, oral contraceptives are an elective risk factor and our study is the most recent meta-analysis to date on the oral contraceptive-breast cancer link. 


In addition to our meta-analysis, it’s important to note that the World Health Organization classified oral contraceptives as a Class I carcinogen in 2005—the most dangerous classification. Even more data has come forth recently in a paper by several researchers—one of whom is a major researcher of the National Cancer Institute—which not only cited our meta-analysis, but found that oral contraceptives increase the risk of triple-negative breast cancer in women under 40 by 320 percent (triple-negative breast cancers are extremely aggressive). (Cancer Epidemiology, Biomarkers & Prevention, April 2009.)


Few in the medical establishment or the public are aware of this data, or if they are, young women almost never hear about them. It’s been almost four years since the publication of our study in the Mayo Clinic Proceedings; I am beginning to think that our study has been effectively “buried.”  Breast cancer and the pill—that dirty little secret? Some day perhaps someone in the media and/or medical establishment will dust a little dirt off those pink ribbons and let young women hear all the facts so they can finally make truly informed decisions.