Even short-term Pill use lowers womb cancer risk ‘for decades’

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Women who’ve used the contraceptive Pill have a reduced risk of womb cancer (also known as endometrial, or uterine, cancer) for more than 30 years after coming off it, research suggests.

“The Pill can also affect a woman’s risk of other cancer types – increasing her risk of breast and cervical cancers"Fiona Osgun, Cancer Research UK

Use of the Pill is already known to offer a degree of protection against both womb and ovarian cancers. But this re-evaluation of virtually all related epidemiological evidence looking at womb cancer, funded by Cancer Research UK and the Medical Research Council, shines further light on its effect.

The findings, published in The Lancet Oncology, show that women still have a reduced risk of womb cancer more than 30 years after they stop taking the Pill. So those who use it when in their 20s and 30s could continue to benefit into their 50s and beyond, when the risk of developing cancer typically becomes greater.

The researchers, from the Collaborative Group on Epidemiological Studies on Endometrial Cancer, say that the longer the Pill is used, the greater the reduction in risk. Even taking it for just a few years appears to give substantial long-term protection.

Fiona Osgun, health information officer at Cancer Research UK, said that the study built on previous research.

“We already know that taking the Pill is linked with a long-term reduction in womb cancer risk,” she said.

“And this large study adds more data on how long this effect lasts – showing that women’s risk of womb cancer is reduced for over 30 years after they’ve stopped taking the Pill.

“The Pill can also affect a woman’s risk of other cancer types – increasing her risk of breast and cervical cancers, but also reducing her chances of developing ovarian cancer.”

The study included data on 27,276 women with endometrial cancer in 36 studies from North America, Europe, Asia, Australia and South Africa.

The findings suggest that for every five years a woman takes oral contraceptives, her risk of endometrial cancer is reduced by around a quarter.

The authors calculate that, in absolute terms, for every 100 women taking the Pill for 10 years, one fewer woman would develop cancer, compared to 100 women not taking the Pill (a drop from 2.3 cases per 100, to 1.3 cases). Over the last ten years this has added up to hundreds of thousands of cases of cancer avoided, the authors say.

“Over the past 50 years, we estimate that about 400,000 endometrial cancers have been prevented in women before the age of 75 years in high-income countries through the use of oral contraceptives, with about 200,000 prevented during the last decade,” commented study author Dr Naomi Allen.

References

  • Collaborative Group on Epidemiological Studies on Endometrial Cancer. (2015). Endometrial cancer and oral contraceptives: an individual participant meta-analysis of 27 276 women with endometrial cancer from 36 epidemiological studies. The Lancet Oncology. DOI: 10.1016/S1470-2045(15)00212-0