Oral contraceptives and breast cancer risk overall and by molecular subtype among  young women

Elisabeth F Beaber; Kathleen E Malone; Mei-Tzu Chen Tang; William E Barlow; Peggy L Porter; Janet R Daling; Christopher I Li

doi:10.1158/1055-9965.EPI-13-0944

Oral contraceptives and breast cancer risk overall and by molecular subtype among young women

Beaber EF, Malone KE, Tang MT, Barlow WE, Porter PL, Daling JR, Li CI

Published May 2014 Cancer Epidemiology, Biomarkers & Prevention : a Publication of the American Association for Cancer Research, Cosponsored by the American Society of Preventive Oncology, 23(5), 755-764

DOI 10.1158/1055-9965.EPI-13-0944 PMID 24633144 PMC PMC4032363

RRM Academy Synopsis

Birth Control Pill Use Linked to Breast Cancer Risk in Young Women

Long-term birth control pill use was linked to higher odds of breast cancer in women ages 20 to 44. Risk estimates were higher in women under 40 and in estrogen receptor-negative and triple-negative tumors. A case-control study compared 985 young women with breast cancer to 882 women without it.

Key Findings

Women with 15 or more years of lifetime oral contraceptive use had higher breast cancer risk than women who had not used them (odds ratio 1.5, 95% CI 1.1 to 2.2).
Current pill use for 5 or more years was also tied to higher risk (odds ratio 1.6, 95% CI 1.1 to 2.5), with no difference by pill type.
In women ages 20 to 39, current pill use for 5 or more years was tied to a 3.5-fold increase in estrogen receptor-negative breast cancer (95% CI 1.3 to 9.0).
In the same age group, current pill use for 5 or more years was tied to a 3.7-fold increase in triple-negative breast cancer (95% CI 1.2 to 11.8).
Among women ages 20 to 39 with 5 or more years of current use, the higher estimates for estrogen receptor-negative and triple-negative tumors were not statistically different from estrogen receptor-positive tumor risk.

Interpretation

This case-control study enrolled 985 women with breast cancer and 882 without it, all ages 20 to 44, living near Seattle and diagnosed between 2004 and 2010. A case-control study compares women who have a disease to women who do not, to look for links to an exposure. The findings support larger studies of pill use and breast cancer by tumor type.

RRM Context

Restorative reproductive medicine treats the root causes of reproductive and hormonal conditions instead of masking them with suppressive medications like the pill. Other studies on the pill and breast cancer span a range of results. A pooled analysis of 54 studies found a modest risk during and shortly after current use, which faded 10 or more years after stopping. The Nurses' Health Study II found a 33% higher risk among current users under 55. The Women's CARE Study found no link among women ages 35 to 44.

Our editorial summary of this paper, not the article's abstract.

Abstract

Background

Evidence suggests that recent oral contraceptive (OC) use is associated with a small increased breast cancer risk; yet risks associated with contemporary OC preparations and by molecular subtype are not well characterized.

Methods

We conducted a population-based case-control study of invasive breast cancer among women ages 20 to 44 residing in the Seattle-Puget Sound area from 2004 to 2010 (985 cases and 882 controls). We collected information on contraceptive use and participant characteristics via an in-person interview. Multivariable-adjusted logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (CI).

Results

Lifetime duration of OC use for ≥ 15 years was associated with an increased breast cancer risk (OR, 1.5; 95% CI, 1.1-2.2). Current OC use (within 1 year of reference date) for ≥ 5 years was associated with an increased risk (OR, 1.6; 95% CI, 1.1-2.5) and there were no statistically significant differences in risk by OC preparation. Risk magnitudes were generally greater among women ages 20 to 39, and for estrogen receptor-negative (ER(-)) and triple-negative breast cancer (current use for ≥ 5 years among ages 20-39: ER(-) OR, 3.5; 95% CI, 1.3-9.0; triple-negative OR, 3.7; 95% CI, 1.2-11.8), although differences between groups were not statistically significant.

Conclusions

Long-term use of contemporary OCs and current use for ≥ 5 years was associated with an increased breast cancer risk among women ages 20 to 44. Risk may be greater among younger women and for ER(-) and triple-negative breast cancer, but these findings require confirmation.

Impact

Continued surveillance and pooled analyses of OC use and breast cancer risk by molecular subtype are needed as OC preparations evolve.

Topics

General Gynecology › Breast Health › Breast Cancer Risk · Contraception › Oral Contraceptives › Cancer Risk

Elisabeth F Beaber, Kathleen E Malone, Mei-Tzu Chen Tang, William E Barlow, Peggy L Porter, Janet R Daling, Christopher I Li

E Beaber, K Malone, M Tang, Bill Barlow, Will Barlow, Billy Barlow, W Barlow, Margaret Porter, P Porter, J Daling, Chris Li, C Li

PMID 24633144 24633144 DOI 10.1158/1055-9965.EPI-13-0944 10.1158/1055-9965.EPI-13-0944 Beaber et al. 2014, Beaber 2014

Keywords

Contraceptives, Oral, Receptors, Estrogen