Prempro Side Effects Double Risk of Death from Breast Cancer: Study

The findings of a new study link the side effects of Prempro, a Pfizer hormone replacement therapy (HRT) drug, with an increased risk of death due to breast cancer. 

The study was conducted as part of the U.S.-funded Women’s Health Initiative (WHI) and was published this week in the Journal of the American Medical Association (JAMA). Previous studies, including one from WHI, have already determined that the chances of contracting breast cancer were increased with Prempro use, but the latest study found that women with breast cancer after using Prempro were twice as likely to die as women who developed breast cancer while not on the hormone replacement therapy.

U.S. researchers looked at a total of 16,608 postmenopausal women between the ages of 50 and 79 with no prior hysterectomy. The women were given either HRT pills or placebos. The original clinical trial was concluded in March 2005, and researchers went back to check on the rates of breast cancer development among the women.

They found that not only was Prempro associated with more invasive forms of breast cancer than women who were given the placebo developed, but researchers also found that women who developed breast cancer after using Prempro had double the risk of death than women who developed breast cancer after being given a placebo.

Pfizer officials have questioned the study’s results, pointing out that some previous studies showed lowered mortality in women who used Prempro.

Hormone replacement therapy involves the use of hormones and progestins to artificially boost hormone levels in women undergoing menopause due to surgery or in postmenopausal women, to provide relief from symptoms such as hot flashes, irregular menstruation or weight gain.

Pfizer currently faces about 9,000 Prempro lawsuits, which were filed against its Wyeth unit by women who claim they developed breast cancer from HRT.

On the same day the JAMA study was released, an Arkansas jury found in favor of the drug maker in a Prempro breast cancer lawsuits filed by Margaret Wilson, a 68-year-old former bank teller who alleged that she developed breast cancer as a result of the hormone replacement therapy. However, the drug maker has lost 7 out of 12 prior cases involving the drug that have reached trial, many resulting in multi-million dollar verdicts.

Earlier this month, an appeal filed by Pfizer was rejected by the Supreme Court, which will force the drug maker to face more than a hundred hormone replacement therapy lawsuits over breast cancer in Minnesota state court.