Updated product information for prescribers and patients to reflect findings from a published meta-analysis. There has been no new evidence since the meta-analysis was published in 1996 .

Introduction

A collaborative meta-analysis of 54 epidemiological studies, published in 1996, showed that there is a small increased risk of being diagnosed with breast cancer in women who are taking the oral contraceptive pill 1 . Doctors and pharmacists were notified of this in June 1996 and were sent information which could be copied and given to patients.

Whilst the findings might be explained by the biological effects of oestrogens on the breast, it is also possible that they may reflect earlier diagnosis in these women. The possible small increased risk of breast cancer has to be weighed against the established benefits of oral contraceptives. This article is intended to inform health professionals of the changes that are being introduced in the SPCs (data sheets) and patient information leaflets, so that they can discuss the matter with patients as appropriate.

Combined oral contraceptives

The statement, which will appear in the SPCs for all combined oral contraceptives, is as follows:

"A meta-analysis from 54 epidemiological studies reported that there is a slightly increased relative risk (RR = 1.24) of having breast cancer diagnosed in women who are currently using combined oral contraceptives (COCs). The observed pattern of increased risk may be due to an earlier diagnosis of breast cancer in COC users, the biological effects of COCs, or a combination of both. The additional breast cancers diagnosed in current users of COCs, or in women who have used COCs in the last ten years, are more likely to be localised to the breast than those in women who never used COCs.

Breast cancer is rare among women under 40 years of age whether or not they take COCs. Whilst this background risk increases with age, the excess number of breast cancer diagnoses in current and recent COC users is small in relation to the overall risk of breast cancer (see bar chart).

The most important risk factor for breast cancer in COC users is the age women discontinue the COC; the older the age at stopping, the more breast cancers are diagnosed. Duration of use is less important and the excess risk gradually disappears during the course of the 10 years after stopping COC use such that by 10 years there appears to be no excess.

Breast cancer and the COC pill

The possible increase in risk of breast cancer should be discussed with the user and weighed against the benefits of COCs taking into account the evidence that they offer substantial protection against the risk of developing certain other cancers (e.g.ovarian and endometrial cancer)."

Progestogen-only contraceptives

A similar but shorter statement will appear in the SPCs of progestogen-only pills (POPs), reflecting the fact that the evidence is based on much smaller populations of users and so is less conclusive than that for COCs. The SPC will point out that the excess number of breast cancer diagnoses in current and recent POP users is small in relation to the overall risk of breast cancer, possibly of similar magnitude to that associated with combined pills. The risk factors are similar to those for the combined pills, with the most important factor being the age at which women discontinue the POP. The excess risk gradually disappears during the course of the 10 years after stopping POP use.

Compared with never-users, among 10,000 women who use POPs for up to 5 years but stop by age 20, the evidence suggests there would be less than 1 extra case of breast cancer diagnosed up to 10 years afterwards. For those stopping by age 30 after 5 years use of the POP, there would be an estimated 2-3 extra cases (additional to the 44 cases of breast cancer per 10,000 women in this age group never exposed to oral contraceptives). For those stopping by age 40 after 5 years use, there would be an estimated 10 extra cases diagnosed up to 10 years afterwards (additional to the 160 cases of breast cancer per 10,000 never-exposed women in this age group).

For injectable progestogens, the evidence is again less conclusive than for COCs. Risks are probably similar to those for the progestogen-only pills.

References

  1. Collaborative Group on Hormonal Factors in Breast Cancer: Breast cancer and hormonal contraceptives: collaborative reanalysis of individual data on 53,297 women with breast cancer and 100,239 women without breast cancer from 54 epidemiological studies. Lancet 1996: 347, 1713-1727.
  2. Collaborative Group on Hormonal Factors in Breast Cancer: Breast cancer and hormonal contraceptives: further results. Contraception 1996: 54, 1S-106S.