Hormone replacement therapy increases ovarian cancer risk, say scientists

Taking hormone replacement therapy for menopause, even for just a few years, increases the risk of developing two common types of ovarian cancer, according to a study published Thursday in The Lancet.

Most of the research on the potentially harmful effects of hormone replacement therapy (HRT) has focused on whether it causes breast or endometrial cancer or cardiovascular problems. But the studies on whether it increases women’s risk of developing ovarian cancer, according to the Lancet analysis by an international group of scientists, have been too small, poorly designed or inconclusive.

That has meant that regulatory agencies haven’t been able to make solid recommendations about HRT and ovarian cancer. Currently neither the U.S. Food and Drug Administration nor the European Medicines Agency, Europe’s drug regulatory agency, mentions ovarian cancer as a risk related to HRT.

Scientists at Oxford University’s International Collaborative Group on Epidemiological Studies of Ovarian Cancer re-analyzed the available research on the relationship between HRT and ovarian cancer.

Looking at patient data from a total of 52 studies involving nearly 21,500 women with ovarian cancer from North America, Europe and Australia, they determined that women who used HRT for even a few years were about 40 percent more likely to develop the two most common types of ovarian cancer.

For every 1,000 individuals using HRT, there would be about one additional case of ovarian cancer, the study concluded.

“It’s the first time there’s been very definite evidence about the effects of just a few years of hormone replacement therapy,” said Sir Richard Peto, a professor of medical statistics at the University of Oxford in the United Kingdom and co-author of the study.

The risk of developing ovarian cancer decreased over time when women stopped using HRT, according to the study, but those who had used it for at least five years still had an elevated risk of getting ovarian cancer 10 years on. 

 “Obviously, if you use it for a shorter time, the risk is less,” Peto said. “Knowing that there are risks, people who’ve got really bad menopausal symptoms that really affect their quality of life might still want to take hormonal replacement therapy.”

He also emphasized that the study results were not to be confused with taking hormonal birth control, which has been found to decrease the risks of getting ovarian and endometrial cancer.

When women reach menopause, which typically happens in their late 40s or early 50s, their ovaries gradually stop producing reproductive hormones such as estrogen and progesterone. As a result, they can experience uncomfortable symptoms such as hot flashes, night sweats and vaginal dryness. Decreased estrogen production is also tied to osteoporosis, a disease in which the bone density decreases, making them more brittle and easily breakable.

In order to counter these symptoms, some women choose to take replacement hormones. The use of HRT peaked in the 1990s, but it dropped off after it was determined that it was associated with certain potentially fatal risks.

In 2002, the National Institutes of Health Women’s Health Initiative halted a study tracking more than 16,000 women taking the HRT drug Prempro, a combination of estrogen and progestin, which they were testing to see whether it could also protect women from heart disease.

The scientists were surprised to discover (PDF) that not only did Prempro not appear to have cardiovascular benefits, it was found to increase the risk of heart attack, stroke and blood clots as well as elevate the risk of developing invasive breast cancer.

After that, the number of women taking HRT plummeted, according to Lancet study, and the FDA recommended it be taken at the lowest dose possible and for the shortest amount of time in order to treat women’s menopause-related symptoms.

Today, about 6 million women in the U.S. and the U.K. take hormone replacements, the study said.