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Modern hormonal contraception associated with increased risk of breast cancer
Clinical Question
Are modern hormonal contraceptives associated with an increased risk of breast cancer?
Bottom line
In this large, well-executed, prospective cohort study, longer exposure to hormonal contraceptives (HCs) was associated with an increased incidence of breast cancer. The dose-response relationship, biological plausability, and coherence with other research argues that this association is causal. However, the absolute risk increase is small—approximately 13 additional breast cancers per 100,000 person-years (number needed to treat to harm = 7690)—and must be balanced against the important benefits of contraception and the maternal mortality rate of 26 per 100,000 pregnancies in the United States, which is the highest in the developed world. 2b
Reference
Study design: Cohort (prospective)
Funding: Industry
Setting: Population-based
Synopsis
Studies have identified an association between HC use and breast cancer, but most of these data are older and are based on higher estrogen doses, were limited to oral contraceptives, and did not study newer progestins. The current study used data from all women in Denmark between the ages of 15 years and 49 years in 1995, and any women who turned 15 before 2012 were included. Those with a history of cancer, venous thromboembolism, or infertility were excluded, leaving nearly 1.8 million women in the final study cohort. Cases of cancer were identified using a national cancer registry, and HC use was culled from the national prescribing database. HC use was defined as current use or recent use (discontinued within the past 6 months) or previous use (discontinued more than 6 months ago). The analysis was adjusted for education, parity, endometriosis, polycystic ovarian syndrome, smoking, body mass index, and a family history of breast or ovarian cancer. The mean duration of follow-up was approximately 11 years, with a total of 19.6 million person-years of follow-up. There were 14 million person-years of follow-up for the first HC used by women, and during that time there were 9101 breast cancers. Overall, the risk of having a diagnosis of breast cancer was significantly higher among recent or current users of HC than among never users (relative risk 1.20; 95% CI 1.14 - 1.26). There was a dose-response relationship between years of exposure to HC and the relative risk of breast cancer, with the relative risk increasing from 1.09 with less than a year of use to 1.38 with more than 10 years of use. The increased risk persisted, especially for women who had taken HC for longer than 5 years.
Reviewer
Mark H. Ebell, MD, MS
Professor
University of Georgia
Athens, GA
Comments
Cet article montre bien qu’il y a un certain danger à la contraception orale à long terme et il faudra inclure ce risque dans la discussion avec les femmes. Il est bon que le réviseur a inclut le taux de mortalité maternel pour relativiser l’information
Not sure how to incorporate this information. My current practice likely won't be changed as absolute risk is so small. Don't agree with some of the inclusion criteria (15 yrs old 2012 - means they are only 21 yrs old now) Inclusion should have included older women only as the younger age may dilute the numbers (breast cancer risk in 20yr olds very low) More interesting would be the stats for women who use current OCPs in their 20's for greater than 5 years - what is their risk of developing cancer later in life as compared to non-users.
Good poem
The comment that US, the most expensive health care system, has the highest maternal mortality rate, 26 per 100,000 women years, supports an inequitable delivery of care.
I can’t access the original article so I am not sure what is included in “hormonal contraception”. I feel I need more guidance on how to incorporate this into my practice, because the phrase “increase your risk of breast cancer” will scare away many women who really need reliable contraception...
Good poem. I already discuss potential risk factors otherwise it is not an informed decision. I will incorporate this as one of the risk factors associated with these types of medications but try and balance this with the actual likelihood it would occur. At this point to not say anything would be highly unethical and very problematic for those unfortunate patients who are affected.
Did they look at age of onset of exposure as a factor?
Les études rétrospectives de cohortes ne peuvent corriger pour tous les biais et ne peuvent que montrer une possible association. Le risque de cancer du sein est tellement minimalement augmenté qu’il est cliniquement non signifiacatif et probablement dû à un biais de sélection ou à une association qui n’a pas été corrigée. Je crois que les contraceptifs ont nettement plus de bénéfices que d’inconvenients et que le fait de les présenter comme un facteur de risque de cancer du sein peut être néfaste. Il faut se rappeler qu’ils ont aussi été démontrer diminuer les cancers de ovaires...
on devrait se demander si la mortalité toutes causés est diminuée chez les utilisatrices de C.O. ou non.
Should give the benefits of OCPs as well; ie the breast CA risk is offset by endometrial, ovarian and colon CA protection with the OCPs.