Oral contraceptives may have played a role in preventing up to 200,000 cases of endometrial cancer in the last ten years, researchers say today.
Researchers from Oxford University, UK, analysed figures on 27,276 women who were diagnosed with endometrial cancer and took part in 36 earlier studies from North America, Europe, Asia, Australia, and South Africa.
Professor Valerie Beral and her team say this comprises "virtually all the epidemiological evidence ever collected on the effect of oral contraceptives".
The analysis shows that the risk of endometrial cancer may be reduces by about a quarter for every five years spent on the pill. The team calculate that, in high-income countries, the risk of developing endometrial cancer before age 75 is cut from 2.3 to 1.3 cases per 100 users after ten years of use.
Behind this apparent benefit is a protective effect from the hormone oestrogen contained in the pill, say the authors in today’s (5 August) issue of the Lancet Oncology. The benefit was not affected by women’s reproductive history, amount of body fat, alcohol or tobacco use, or ethnicity.
Professor Beral says: "The strong protective effect of oral contraceptives against endometrial cancer – which persists for decades after stopping the pill – means that women who use it when they are in their 20s or even younger continue to benefit into their 50s and older, when cancer becomes more common.
"Previous research has shown that the pill also protects against ovarian cancer. People used to worry that the pill might cause cancer, but in the long term the pill reduces the risk of getting cancer."
Dr Clare McKenzie, a vice-president of the Royal College of Obstetricians and Gynaecologists, welcomed the findings.
She said: "The results should reassure women of the protective effect the combined pill has against womb cancer, but it’s important to remember a third of cases are linked to a women being overweight or obese, so keeping a healthy bodyweight is the most important factor in reducing risk.”
Collaborative Group on Epidemiological Studies on Endometrial Cancer. Endometrial cancer and oral contraceptives: an individual participant meta-analysis of 27276 women with endometrial cancer from 36 epidemiological studies. Lancet Oncology 5 August 2015; doi: 10.1016/S1470-2045(15)00212-0
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