There has been much uncertainty regarding the risk of cancer associated with taking hormone replacement therapy (HRT) for the menopause. An analysis of all available evidence published in The Lancet today shows that HRT, even when taken for only a few years, significantly increases the risk of developing the two most common types of ovarian cancer.
The use of HRT increased rapidly during the 1990s to protect women against bone loss and symptoms associated with the reduction in oestrogen that occur as a result of the menopause. When a large study reported that HRT increased the risk of cancer, use fell rapidly about a decade ago. Currently, about 6 million women the UK and USA are still taking HRT. Existing WHO, US and European HRT guidelines do not mention ovarian cancer, and UK guidelines (currently being revised) state that ovarian cancer might be increased with long-term use.
The Collaborative Group on Epidemiological Studies of Ovarian Cancer analysed pooled data from 21,488 women with ovarian cancer who participated in 52 epidemiological studies. The results showed that there was a significantly increased risk of developing ovarian cancer in current or recent users of HRT but the risk reduced over time after stopping HRT. However women who had used HRT for at least 5 years still had a slightly increased risk of ovarian cancer 10 years later.
Study co-author Professor Sir Richard Peto from the University of Oxford explained: For women who take HRT for 5 years from around age 50, there will be about one extra ovarian cancer for every 1000 users and one extra ovarian cancer death for every 1700 users.
The effect of HRT on the risk of developing ovarian cancer was the same for both oestrogen-only replacement therapy and oestrogen plus progestagen replacement therapy. Similarly, it was not affected by the age at which HRT began, body size, past use of oral contraceptives, hysterectomy, alcohol use, tobacco use, or family history of breast or ovarian cancer.
It should be noted, however, that an increase in risk was only observed for two main types of ovarian cancer (serous and endometrioid ovarian cancers), and not for the two less common types (mucinous and clear cell ovarian cancers).
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Study co-author Professor Dame Valerie Beral from the University of Oxford commented “The definite risk of ovarian cancer even with less than 5 years of HRT is directly relevant to today’s patterns of use—with most women now taking HRT for only a few years—and has implications for current efforts to revise UK and worldwide guidelines.”
Now it is known that HRT uses carries a definite risk of ovarian cancer, even when used for less than 5 years, medical advice to inform personal choices and worldwide guidelines will need to be revised to reflect this.
Collaborative Group on Epidemiological Studies of Ovarian Cancer. Menopausal hormone use and ovarian cancer risk: individual participant meta-analysis of 52 epidemiological studies. Lancet 2015; Epub ahead of print. Available at http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(14)61687-1/abstract