The Pill Causes Breast Cancer

A meta-analysis published in the October issue of Mayo Clinic Proceedings¹ indicts oral contraceptives as putting premenopausal women at significantly increased risk for breast cancer, especially women who use them prior to having a child.

The meta-analysis builds on many studies with similar findings. But even as the findings stack up, many women are unaware of the risks posed by oral contraceptive use prior to pregnancy, says lead study author Chris Kahlenborn, M.D., of Altoona Hospital in Altoona, Pa. Dr. Kahlenborn says the discrepancy between risk and patient awareness prompted the meta-analysis, which involved extracting data from 34 studies on whether oral contraceptive (OC) use is associated with premenopausal breast cancer. Included in the studies were women who were premenopausal or younger than 50 and who had been, in most cases, diagnosed with breast cancer during or after 1980.

The major findings from this careful analysis of the world literature were that oral contraceptives (OCs) were linked with a measurable and statistically significant association with pre-menopausal breast cancer.  The risk association was 44% over baseline in parous women (having been pregnant) who took OCs prior to their first pregnancy. The study re-enforces the recent classification of OCs as Type 1 carcinogens by the International Agency for Cancer Research².

These are staggering results given that 47,000 women each year (in the USA) develop breast cancer prior to menopause.

According to Dr. Kahlenborn, extraction of reliable data from the world literature is an extremely difficult task because no two studies are exactly alike.  However, meta-analysis is a valid statistical tool that has the ability to identify associations and potential risk.  He said the present research team was very careful to clearly present how the data were collected and processed, and welcomes opportunities for open and critical debate on this important subject by professionals as well as the lay public.

Rather, patients should know that sustained oral contraceptive use prior to pregnancy increases a premenopausal woman's risk of developing breast cancer, says Dr. Kahlenborn. He says physicians should better inform their patients of the risks associated with oral contraceptives and calls it a "clear-cut informed consent issue."

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