HT use associated with increased risk for ovarian cancer

Past and current users of hormone therapy are at increased risk for ovarian cancer compared with women who have never taken hormones, according to data published in JAMA today. The risk remained regardless of duration of use, formulation, regimen, estrogen use or route of administration.

The study included Danish women aged 50 to 79 from 1995 to 2005 through linkage to Danish national registries. The researchers gathered data on HT use and ovarian cancer incidence. The analysis included 909,946 women without hormone-sensitive cancer or who had not had both ovaries removed.

About 63% of women had never used HT, 22% were past users and 9% current users. Forty-six percent of current users had used hormones for more than seven years.

Researchers identified 3,068 cases of ovarian cancer during eight years of follow-up; 2,681 were epithelial tumors.

Women who were current users of HT had an overall 38% increased risk for ovarian cancer compared with women who never used hormones. With regards to epithelial cancer, the relative risk among current HT users was 44% higher — previous HT users had a 15% increased risk vs. never-users.

Risk for ovarian cancer declined with longer time since HT use: zero to two years, RR=1.22; more than six years, RR=0.63.

Researchers calculated an absolute risk of approximately one extra ovarian cancer for roughly 8,300 women taking HT each year.

“If this association is causal, use of hormones has resulted in roughly 140 extra cases of ovarian cancer in Denmark over the mean follow-up of eight years, i.e., 5% of the ovarian cancers in this study. Even though this share seems low, ovarian cancer remains highly fatal, so accordingly this risk warrants consideration when deciding whether to use HT,” the researchers concluded.

Mørch LS. JAMA. 2009;302:298-305.