HRT increases ovarian cancer risk

Women who are currently on hormone replacement therapy or have taken it in the past are at increased risk of ovarian cancer, according to the results of a large study.

The data mirrors the results from an earlier study in 2002.

Compared with women who have never taken hormone therapy (HRT), those who currently take it or who have taken it in the past are at increased risk of ovarian cancer, regardless of the type or length of treatment, according to the study.

In absolute terms the use of HRT was linked to one extra case of ovarian cancer each year for every 8,300 women taking the treatment. In the eight years of the study, HRT was linked to a total of 140 extra cases of ovarian cancer out of a total of 2,800.

Prevention of ovarian cancer is challenging because little is known about its cause. Studies have suggested an increased risk of ovarian cancer among women taking post-menopausal hormone therapy (HT), with little known about the effects of different forms of treatment.

About the study

The Danish study included all Danish women age 50 to 79 from 1995 through 2005. The analysis included over 909,900 women without hormone-sensitive cancer or who had not had both ovaries removed. At the end of the follow-up, 63% of the women had not been taking HT, 22% were previous users of hormones, and 9% current users of hormones. Among the current users, 46% had used hormones for more than 7 years.

During an average of 8 years of follow-up, 3,068 ovarian cancers were detected. Of these, 2,681 were epithelial tumors (a type of ovarian cancer). Compared with those who had never used HT, current users of HT had an overall 38% increased risk of ovarian cancer. When restricting the analyses to epithelial ovarian cancer, the relative risk among current HT users was 44% higher, with previous HT users having a 15% greater risk compared with women who had never used HT. The risk for ovarian cancer and epithelial ovarian cancer did not increase significantly with increasing durations of HT.

The risk of ovarian cancer declined as the gap since last treatment increased.The type of treatment made little difference to the risk.

The researchers estimate that use of HT was a factor in 5% of all cases of ovarian cancer in the study. While not a large percentage, the fact that ovarian cancer is often fatal means that this should be considered when deciding to use HRT.

This article was published on Thu 16 July 2009