A recent study has found that the current or recent use of progestagen-only contraceptives, increasingly popular among premenopausal women, is associated with a slightly increased risk of breast cancer. The study, conducted using the UK’s Clinical Practice Research Datalink (CPRD) database, aimed to assess breast cancer risk in relation to the use of various hormonal contraceptives, with a focus on progestagen-only preparations. The findings were published in the journal PLOS Medicine.
The nested case-control study included 9,498 women aged under 50 with invasive breast cancer diagnosed between 1996 and 2017, and 18,171 closely matched controls. Researchers had an average of 7.3 years of clinical records for each case and control before the diagnosis date. Conditional logistic regression was used to calculate the odds ratios (ORs) and 95% confidence intervals (CIs) of breast cancer based on the last hormonal contraceptive type prescribed, controlled for factors such as age, GP practice, body mass index, number of recorded births, time since last birth, and alcohol intake.
The study found that 44% of women with breast cancer and 39% of matched controls had a hormonal contraceptive prescription an average of 3.1 years before breast cancer diagnosis (or equivalent date for controls). About half of the prescriptions were for progestagen-only contraceptives. Breast cancer ORs were similarly and significantly raised for all types of hormonal contraceptives, including oral combined, oral progestagen-only, injected progestagen, and progestagen-releasing intrauterine devices (IUDs).
Meta-analyses combining the CPRD results with 12 previous observational studies found significantly raised relative risks (RRs) for current or recent use of progestagen-only contraceptives. The study estimates that the 15-year absolute excess risk associated with five years of oral combined or progestagen-only contraceptive use in high-income countries ranges from 8 per 100,000 users for ages 16 to 20 years to 265 per 100,000 users for ages 35 to 39 years.
The main limitation of the study was the lack of information on contraceptive use before entry into the CPRD database. As a result, the findings provide evidence of short-term associations between hormonal contraceptives and breast cancer risk, but not of longer-term associations or the impact of the total duration of contraceptive use on breast cancer risk.
The study highlights the need to consider the slight increase in breast cancer risk associated with progestagen-only contraceptives and combined hormonal contraceptives in the context of their benefits during the childbearing years. As the underlying risk of breast cancer increases with age, the absolute excess risk associated with oral contraceptive use is estimated to be smaller for women who use it at younger rather than older ages.
The research findings are significant as they provide new insights into the association between the use of progestagen-only contraceptives and breast cancer risk. In recent years, progestagen-only contraceptives have gained popularity, with nearly as many prescriptions for these contraceptives as for combined oral contraceptives in England in 2020. As more women opt for progestagen-only contraceptives, it is crucial to understand their potential impact on breast cancer risk.
The study’s results indicate a relative increase of approximately 20% to 30% in breast cancer risk associated with the current or recent use of either combined oral or progestagen-only contraceptives. However, it is essential to emphasize that the increased risk must be viewed alongside the well-established benefits of contraceptive use during women’s reproductive years.
Healthcare professionals should take these findings into account when discussing contraceptive options with their patients, ensuring that women have the information necessary to make informed decisions about their contraceptive choices. While the study’s findings point to a slight increase in breast cancer risk, the overall risk remains relatively low, especially when compared to the benefits of contraception use.
The study’s limitations, such as the lack of complete information on a woman’s prescription history, mean that further research is needed to better understand the long-term associations of contraceptive use on breast cancer risk. Nonetheless, the findings offer valuable information on the short-term associations between hormonal contraceptives and breast cancer risk, serving as a useful reference point for healthcare professionals and patients alike.
The study has found that current or recent use of progestagen-only contraceptives is associated with a slightly increased risk of breast cancer, similar in magnitude to the risk associated with combined hormonal contraceptives. While this information is essential for informed decision-making, it is crucial to consider these risks alongside the benefits of contraceptive use during women’s reproductive years. As research continues to explore the potential long-term associations of contraceptive use on breast cancer risk, healthcare professionals should work with their patients to help them make the best possible choices for their individual needs and circumstances.