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Effects of Birth Control Pills on Breast Tissue

Anna Wu, PhD, Heather Macdonald, MD, Claire Templeman, MD, Linda Hovanessian-Larsen, MD, Michael Press, MD, Debra Hawes, MD, Frannk Stanczyk, PhD, Malcolm Pike, PhD, and C. Leigh Pearce, PhD, University of Southern California
Study abstract

Experimental and epidemiological studies show that both estrogens (e.g. EE2) and progestins (e.g. NET) can increase breast‐cell proliferation but the dose response has not been well studied as it relates to either hormone and our understanding is very incomplete. Epidemiological studies have not convincingly shown any dose‐effect relationships with the components of oral contraceptives (OCs) and breast cancer risk; however, retrospective studies of history of OC use suffer from great errors of recall of OC brand, in particular of dose of estrogen and progestin in the OC, and this problem is aggravated by the fact that many women have used many brands (and doses) of OC. The aim of this study is to continue our efforts to remedy this lack of reliable information by studying the effects of changing the dose of EE2 and the dose of a commonly prescribed progestin, norethisterone (NET), on breast‐cell proliferation in healthy volunteers ages 18 to 35 by providing the OC for three months of use and obtaining a small amount of breast tissue for immunohistochemistry and microdissection to separate out the various tissue types to be analyzed by microarray analysis on commercially available affymetrix chips.

Study review

The purpose of this study at the University of Southern California in Los Angeles, CA, is to gain a better understanding of the changes that may occur in the breast when women use oral contraceptives (birth control pills) that contain different levels of the hormones estrogen and progestin. The researchers wanted to enroll 85 women. The Call to Action for this study was sent to Army of Women members on February 1, 2012. The researchers were able to close enrollment on March 29, 2013, after the Army of Women provided them with 120 women who were interested in enrolling in the study.