Long-term reduction in endometrial cancer risk with oral contraceptives

By Bianca Nogrady
Oral contraceptive use is associated with a long-term reduction in the risk of endometrial cancer, according to a large meta-analysis.

Analysis of data from 36 epidemiological studies involving 27,276 women with endometrial cancer and 115,743 controls showed women who had used oral contraceptives had a nearly one-third reduction in their risk of endometrial carcinoma compared with women who had never used them.

Researchers found that every five years of oral contraceptive use was associated with a one-quarter reduction in the risk of endometrial carcinoma, even after accounting for factors such as BMI, parity and use of hormone replacement therapy, according to a paper published in The Lancet Oncology.

This reduction in risk was evident even 30 years after the woman had stopped taking oral contraceptives, and was similar across age groups, despite the use of higher oestrogen pills in the earlier years of oral contraceptives.

Oral contraceptives appeared to offer greater protection against carcinomas than sarcomas, although the numbers of sarcomas were small.

‘In high-income countries, 10 years use of oral contraceptives was estimated to reduce the absolute risk of endometrial cancer arising before age 75 years from 2.3 to 1.3 per 100 women,’ the authors wrote.

Commenting on the study, Dr Deborah Bateson said it provided strong evidence that there were unintended benefits of oral contraceptive use, as well as risks.

‘We often concentrate on the risks of contraception but it’s important for women to have information on the benefits as well,’ said Dr Bateson, Medical Director of Family Planning NSW.
Dr Bateson told Medicine Today that the large size of the pooled study population and long duration of follow up were important in supporting a greater understanding of the long-term impacts of oral contraceptive use.

‘Endometrial cancer is often diagnosed many years or even decades after a woman has stopped taking the pill, and this very large meta-analysis provides reassuring evidence about the long term benefits of the contraceptive pill which persist beyond the time that the pill is stopped.’

However, she also stressed that the absolute risk of endometrial cancer was relatively low, and that despite the reduction in risk, there was not enough current evidence to warrant use of the oral contraceptives as a preventative measure in women at greater risk of endometrial cancer.

Lancet Oncol 2015; http://dx.doi.org/10.1016/S1470-2045(15)00212-0.

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