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

Publication Type:

Journal Article

Source:

Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology, Volume 23, Issue 5, p.755-64 (2014)

Keywords:

2014, April 2014, Center-Authored Paper, Collaborative Data Services Core Facility, Epidemiology Core Facility, Human Biology Division, Public Health Sciences Division, Shared Resources

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 20-44 residing in the Seattle-Puget Sound area from 2004-2010 (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 20-39, 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), though 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 20-44. 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.