Impact of Modern Hormonal Contraceptives on Breast Cancer Risk

Prevalence of Hormonal Contraceptives

Modern hormonal contraceptives are widely used by women around the globe, with estimates suggesting that over 140 million women utilize these methods for family planning. The role of estrogen in the development of breast cancer has been established, yet the relationship between hormonal contraception and breast cancer risk remains uncertain, particularly as new hormonal formulations, such as progestin, emerge.

Research Gaps on Progestin

Research examining the implications of hormonal contraceptives containing progestin is limited. Most existing studies have focused on post-menopausal women, leaving a significant knowledge gap regarding pre-menopausal women who have used hormonal contraceptives from a young age. This highlights the need for further investigation into this demographic.

Study Overview by Lina Morch and Team

A research team led by Lina Morch at the University of Copenhagen has recently explored the relationship between breast cancer risk and the use of hormonal contraceptives among women in Denmark. Their findings were published in the New England Journal of Medicine. The study utilized nationwide registries to analyze data from women aged 15 to 49, examining their use of hormonal contraceptives, breast cancer diagnoses, and other relevant information. The research followed 1.8 million women over an average period of 10.9 years.

Findings on Breast Cancer Risk

The study identified just over 11,500 new breast cancer cases. A comparison revealed that women who had used hormonal contraceptives exhibited a higher risk of breast cancer than those who had not. This risk appeared to escalate with the duration of contraceptive use. Notably, women who ceased using hormonal contraceptives for more than five years still had a heightened risk compared to those who had never used them. Additionally, those who utilized a progestin-only intrauterine device (IUD) also showed an increased risk.

Limitations of the Study

Despite the significant findings, the study had some limitations. Certain factors, such as physical activity, alcohol consumption, and breastfeeding, could not be adjusted for, despite their known association with breast cancer. Furthermore, women who had previously used hormonal contraceptives without any recorded data were not included in the analysis.

Conclusion on Hormonal Contraceptive Use

The research concluded that there is a slight increase in breast cancer incidence among women using hormonal contraceptives compared to those who have never used them. This elevated risk persists even after discontinuation of hormonal contraceptive use for an extended period. It is important to note, however, that while a correlation was identified between hormonal contraceptive use and breast cancer risk, the absolute increase in risk was minimal.

Reference

Morch, L.S., et al. 2017. Contemporary hormonal contraception and the risk of breast cancer. N Engl J Med. 377: 2228-2239.