March 21, 2023

expert reaction to study looking at the association between hormonal contraceptive use and breast cancer incidence

A study published in PLOS Medicine looks at combined and progestagen-only hormonal contraceptives and breast cancer risk.

This Roundup accompanied an SMC Briefing.

Dr Michael Jones, Senior Staff Scientist in Genetics and Epidemiology at The Institute of Cancer Research, London, said:

“These findings suggest the use of hormonal contraceptives is associated with a slight increase in breast cancer risk before the menopause. The results were similar for different types of hormonal contraception, including progestagen-only contraceptives, where less is currently known about their risks. 

“The researchers used data from 9498 women with breast cancer and 18171 without, all under 50 years of age. The statistically significant associations are unlikely to be due to chance because of the large number of breast cancer patients included in the study. The authors also considered various limitations of the data and showed these were unlikely to affect the results.

“The study is based on routinely collected data from general practices that cover about 7% of the UK population, but is broadly representative of the UK on age, sex, and ethnicity. While the results may be generalizable to the UK, prescribing patterns in other developed or developing countries may be different to the UK, and rates of breast cancer also differ around the world, so the impact of hormonal contraceptives may also be different.”

Prof Stephen Duffy, Centre Lead, Centre for Prevention, Detection and Diagnosis, Queen Mary University of London, said:

“These results confirm those of the Collaborative Group on Hormonal Factors in Breast Cancer in the twentieth century, that oral contraceptives are associated with a small but significant increase in risk of breast cancer. In addition, they show that progestagen-only contraceptives have similar effects to those of combined contraceptives. At the time of the Collaborative Group meta-analysis, there was very little data on progestagen-only contraceptives and breast cancer. This study also confirms the reduction in the effect with increasing time since stopping using oral contraceptives. Ten years after stopping there was no excess risk associated with oral contraceptive use. The results are reassuring in that the effect is modest. The Collaborative Group in the past found that the enhanced risk was mainly in less severe disease.”

‘Combined and progestagen-only hormonal contraceptives and breast cancer risk: A UK nested case–control study and meta-analysis’ by Danielle Fitzpatrick et al. was published in PLOS Medicine at 18:00 UK Time Tuesday 21 March 2023.

DOI: 10.1371/journal.pmed.1004188

Declared interests

Dr Michael Jones: “No conflicts to declare.”

For all other experts, no reply to our request for DOIs was received.