WASHINGTON (Reuters) - Two studies published on Wednesday further link hormone replacement therapy with cancer, suggesting -- but not yet proving -- that HRT causes breast and ovarian cancer.

Cancerous breast tissue is seen in an undated handout photo from the National Cancer Institute. Two studies published on Wednesday further link hormone replacement therapy with cancer, suggesting -- but not yet proving -- that HRT causes breast and ovarian cancer. REUTERS/Handout

But doctors stressed that younger women who need the drugs to relieve serious symptoms of menopause should still consider taking them because new, lower-dose formulations are available and doctors now know to prescribe them for shorter periods of time.

One study, published in the Lancet medical journal, found women who used HRT were 20 percent more likely to die from ovarian cancer than similar women who did not use HRT.

Dr. Valerie Beral and colleagues at the Cancer Research UK Epidemiology Unit in Oxford, said their findings suggested that that as many as 1,000 extra women in Britain had died from ovarian cancer between 1991 and 2005 because they were using hormone replacement therapy.

They used data from the “Million Women Study,” which looked at just under a million women, about half of whom were current of former HRT users.

For every 1,000 women who used HRT for five years, 2.6 developed ovarian cancer. That compared to 2.2 cases of ovarian cancer for every 1,000 women who did not use HRT.

“The effect of HRT on ovarian cancer should not be viewed in isolation, especially since use of HRT also affects the risk of breast and endometrial cancer,” Beral’s team wrote.

“The total incidence of these three cancers in the study population is 63 percent higher in current users of HRT than never users,” they added.

“Thus when ovarian, endometrial and breast cancer are taken together, use of HRT results in a material increase in these common cancers.”

FALL IN BREAST CANCER

The second study, published in the New England Journal of Medicine, showed that the incidence of breast cancer dropped by 8.6 percent between 2001 and 2004 in the United States -- along with a decline in HRT use.

Most of the drop in breast cancer cases was seen in 2003, and then rates leveled off in 2004, Dr. Donald Berry of the M.D. Anderson Cancer Center in Houston and colleagues found.

This drop happened right after the 2002 Women’s Health Initiative study found that HRT could raise the risk not only of breast cancer, but of strokes and other serious conditions.

Millions of women stopped taking the drugs, which had been widely prescribed to reduce the risk of heart disease, osteoporosis and in general to keep women feeling “young”.

Berry said the breast cancer statistics suggest, but do not show, that women who stopped HRT avoided breast cancer. The theory is that the hormones help fuel the growth of tumors, so it is possible that more women have small, slow-growing cancers that cannot yet be detected.

Berry said if women follow the current recommendations -- to take HRT for the shortest possible period of time and at the lowest possible dose -- the benefits outweigh the risks.

“If this prevents the hot flashes, at least for a limited time, say a year or two, that might be quite a reasonable and rational choice,” he said.

Dr. Joseph Camardo, head of medical affairs at drugmaker Wyeth , which makes the popular Premarin HRT drugs, said he did not believe the findings should change current guidelines.

“No one believes this information should change clinical practice,” Camardo said in a telephone interview.

“The most important thing is that women speak to the doctor.”