A new study presented by the Woman Health Initiative (WHI) at the San Antonio Breast Cancer Symposium in Texas has revealed that hormone replacement therapy can increase the danger of breast cancer.

The researchers analyzed the effect of hormone medications on the prevention of heart disease, bone loss, and other problems specific to post-menopausal women. The study involved more than 16,000 women matched for age, weight and other issues; the participants were arbitrarily given Wyeth Pharmaceutical’s Prempro, estrogen and progestin, or placebos. The treatment was stopped when researchers noted a 26 percent higher chance of breast cancer in those taking Prempro. The researchers concluded that taking hormone therapy like estrogen and progesterone pills that are prescribed to prevent heart disease, bone loss and other problems after menopause for five years doubles the risk of breast cancer. “These findings also indicate that women who take estrogen plus progestin continue to be at increased risk of breast cancer, even years after stopping therapy,” said National Heart, Lung, and Blood Institute director Dr. Elizabeth G. Nabel, in a press release.

Hormone replacement drugs such as Premarin, Prempro, Premphase and Provera are used to treat hot flashes and other symptoms that accompany menopause.

Wyeth Pharmaceuticals, the drug company that makes Prempro and Premarin faces a growing number of lawsuits filed by and on behalf of women who blame the drugs for their breast cancer. The controversial situation started when Patricia Zandi alleged that she developed breast cancer after she had used Wyeth’s Premarin and Prempro hormone replacement therapies. The company stated that there was no “scientifically valid evidence” to support her claim.

Wyeth is facing 5,300 lawsuits because of the two products, from women who believe that they were harmed by the hormone replacement drugs. These drugs have been used by almost six million women to control the negative effects of menopause such as hot flashes and mood swings, before a study made public in 2002 the relation between the drugs and breast cancer, according to the Times. Wyeth said in their defense that they conducted safety tests on the medicine and warned about potential risks, by including these on prescription labels and information sheets. Women went off their pills, choosing to risk hot flashes and brittle bones rather than heart attacks and breast cancer.

Furthermore, researchers at UCLA found that women who took a combination of estrogen and progestin for more than five years were twice as likely to develop the disease. It is obvious that breast cancer numbers decreased in recent years largely because women stopped hormone therapy and less menopausal women started it, said the study’s leader, Dr. Rowan Chlebowski of Harbor-UCLA Medical Center in Los Angeles.

Breast cancer is one of the top leading causes of cancer death worldwide, with an estimated 500,000 death annually, according to the American Cancer Society. Almost 4,000 people are diagnosed with cancer daily in the United States. On a national level, breast cancer is the second leading cause of cancer death for women, exceeded only by lung cancer.