The University of Oxford has unfortunate news for anyone on the pill, or implant, or hormone-releasing IUDs. A new anaysis from the Oxford Population Health’s Cancer Epidemiology Unit has found that all hormonal contraceptives come with an increased risk of breast cancer:
The researchers analysed data from 9,498 women who developed invasive breast cancer between ages 20 to 49 and 18,171 closely-matched women without breast cancer who acted as controls. The data were collected by the Clinical Practice Research Datalink (CPRD). 44% of women with breast cancer and 39% of women without breast cancer included in the study had a prescription for a hormonal contraceptive an average of three years before diagnosis, around half of whom were last prescribed a progestogen-only contraceptive.
The data were used to calculate the strength of the association between use of each type of hormonal contraceptive and breast cancer risk. These calculations were then adjusted to take into account established risk factors such as body mass index (BMI), number of recorded births, and the time since a woman’s last birth. The researchers combined the CPRD results on oral contraceptive use with those from other previously published studies to estimate absolute excess risks, meaning the additional number of women who would be expected to develop breast cancer in those who used oral contraceptives compared to those who did not.
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You can read the meta-analysis here, at PLOS Medicine.