A new study involving 1.8 million Danish women between 15 and 49 years of age, carried out over eleven years, concluded that the recent or current use of hormonal contraception increases the risk of breast cancer by 20%.
The study, which was reported in the New England Journal of Medicine, shows that although "earlier contraceptives " posed a higher risk of breast cancer, the new forms with lower doses of oestrogen are not exempt either. The longer they are used, the greater the risk: 9% after one year compared to 38% after ten years. Harmful effects could persist for an average of five years after the contraception has been withdrawn.
Scientists have calculated that hormonal contraception triggers an additional case of breast cancer in 7,960 women each year. This is a high incidence rate since "140 million women use hormonal contraception world-wide".
Kevin McConway, Emeritus Professor of Applied Statistics at the English Open University, commented as follows: "Like most other studies on hormonal contraceptives and the risk of breast cancer, this is observational. Therefore, it cannot provide conclusive evidence that hormonal contraception is definitely responsible for the increased risk. However, from a statistical perspective, scientists have highlighted most of the key factors that could also be involved, which is why there is good reason to believe that the increased risks of breast cancer are linked to contraceptives".
According to the American Cancer Society, “255,000 women are diagnosed with breast cancer in the USA each year” and the disease “kills 41,000".
Reuters (06/12/2017) ; The Guardian, Sarah Boseley (06/12/2017)