Faculty of Sexual and Reproductive Healthcare, Royal College of the Obstetricians and Gynaecologists (UK), 22 March 2023
FSRH response to new study on use of combined and progestogen-only hormonal contraception and breast cancer risk:
A new observational study by Fitzpatrick, et al., published in PLOS Medicine investigated the association between current or recent use of combined oral and progestogen-only hormonal contraception and breast cancer risk.
The study focussed on the progestogen-only contraceptive methods, in particular, due to their increasing use in the UK and other settings and the limited information available at present as to whether use of these methods affects breast cancer risk.
Fitzpatrick, et al., demonstrated a slight (20-30%) elevated risk of incidents of breast cancer in women <50 years of age who currently use or have recently used progestogen-only contraceptives. The magnitude of this increase in risk was small and similar across all the types of progestogen-only methods studied (i.e., oral pill, injectable, implant and hormonal IUD). It was also similar to the increased risk found in this same study for combined (estrogen + progestogen) oral contraception and to what has been previously documented for CHC methods.
The researchers also combined their new data on progestogen-only oral contraceptive use and breast cancer risk with data from previous studies of the topic and, from this combined meta-analysis, drew similar conclusions about there being a slightly increased breast cancer risk with progestogen-only oral contraceptive use.
In addition to showing this slight increase in breast cancer risk among individual users of any POC, the study also showed that after 5 years of use of either combined oral or any form of progestogen-only contraception, the associated 15-year absolute excess incidence of breast cancer in high-income countries (meaning the number of extra breast-cancer cases for every 100,000 women on the method) was estimated at 8 cases per 100,000 users at age 16-20 years and 265 cases per 100,000 users at age 35-39 years.
This large and well-conducted observational study, and accompanying meta-analysis, help us to better understand the relationship between progestogen-only contraceptive use and breast cancer risk. Based on these new data, it is possible that use of progestogen-only contraception does slightly increase breast cancer risk among current and recent users. However, breast cancer is relatively rare among younger women — those in the age groups most likely to be using these methods of contraception — so the 20-30% increases in relative risk with POC use observed in this study equate to very small increases in a woman’s absolute risk of developing breast cancer. This means that even with the slight increased risk observed by Fitzpatrick, et al., users and potential users of POC can be reassured that the chances of developing breast cancer as a result of their contraceptive use remain small.
Additionally, any small increase in breast cancer risk to an individual using a progestogen-only contraceptive needs to be weighed against the very significant benefit of achieving effective contraception to avoid unplanned pregnancy and the other non-contraceptive benefits of progestogen-only contraceptive use, including possible decreases in risk of ovarian and endometrial cancers.
How does this affect practice?
The FSRH CEU recommends no significant change to current practice at this time but does suggest that this information is included in individual discussions with patients regarding risks and benefits of various contraceptive methods.