* HRT linked with 5 percent of ovarian cancer cases
* Raised risk of the deadly cancer by 38 percent
By Andrew Stern
CHICAGO, July 14 (Reuters) - Menopausal women who took hormone replacement therapy increased their risk of ovarian cancer by 38 percent, Danish researchers reported on Tuesday.
The study of more than 900,000 Danish women aged 50 to 79 found about one extra ovarian cancer for roughly 8,300 women taking hormone therapy each year.
At the time they got sick, 9 percent of the women were taking hormone therapy, 22 percent were previous users and 63 percent did not take it. The researchers calculated that current hormone use conferred a 38 percent higher risk of contracting the disease compared to non-users over the eight-year study.
Hormone therapy was linked to 140 extra cases of ovarian cancer in Denmark during the eight-year study, accounting for 5 percent of all cases in that period, the researchers reported in the Journal of the American Medical Association.
"Even though this share seems low, ovarian cancer remains highly fatal, so accordingly this risk warrants consideration when deciding whether to use (hormone therapy)," wrote Lina Steinrud Morch and colleagues at Copenhagen University.
The findings were similar to those in the 2002 Women's Health Initiative study, which was stopped early because it found an increased risk of ovarian cancer, breast cancer, strokes and other health problems from hormone therapy or HRT.
HRT use plunged after the WHI study, and sales of U.S. market leader Wyeth's WYE.N combined estrogen-progestin therapy Prempro have fallen by 50 percent since 2001 to around $1 billion a year.
For women considering hormone therapy, "family history comes into play, and your own personal medical history certainly comes into play. Those risks have to be discussed with your doctor," said Wyeth's director of global medical affairs, Dr. Corrado Altomare, who was not involved in the Danish study.
The risks of ovarian cancer were about the same from hormone therapy regardless of the duration of use, the formulation of the hormones, the estrogen dose, or how it was administered, according to the study.
As in earlier studies, it found the cancer risk diminished about two years after therapy was stopped.
Ovarian cancer is difficult to detect before it spreads, and therefore is often fatal. Roughly 18 out of 100,000 U.S. women are diagnosed yearly with the disease, which killed 15,000 Americans in 2007, according to government statistics.
What causes cancer cells to appear in the ovaries in the first place is not known, but estrogen is believed to spur tumor growth and may be a trigger.
Editing by Maggie Fox and Vicki Allen