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Pfizer Hormones Almost Double Breast Cancer Death Risk in Study

Pfizer Inc.’s Prempro, a hormone once used by millions of women to ease menopause symptoms, almost doubled the death risk from breast cancer, a U.S. study found.

The findings from the U.S.-funded Women’s Health Initiative are the first to tie Pfizer’s hormone replacement therapy Prempro, already linked to higher breast cancer and heart disease rates, to increased mortality from tumors.

Pfizer, the world’s largest drugmaker, yesterday won its sixth of 13 jury cases over Prempro’s health risks an hour before the research was reported by the Journal of the American Medical Association. Previous studies suggested tumors fueled by hormone therapy were less aggressive and easier to treat. Pfizer gained Prempro in its $68 billion purchase of Wyeth last year. The hormones had annual sales of more than $2 billion before the study was halted in 2002, leading many women to stop treatment.

“You have more cancers, you have more advanced stage cancers and you aren’t having just more favorable cancers,” lead researcher Rowan Chlebowski, from the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, said in a telephone interview. “Women should think critically about if they need this, if their symptoms are significant and if they would persist.”

Researchers tracked 12,788 women for almost 8 years after the trial was stopped and found 678 cases of invasive breast cancer, including 385 for women taking hormones and 293 with a placebo. Investigators calculated there were 2.6 deaths caused by breast cancer for every 10,000 women taking hormones each year, compared with 1.3 deaths for those on a placebo.

Conflicting Research

The findings conflict with previous studies showing breast cancers in women taking hormone therapy had a lower risk of death, said Christopher Loder, a spokesman for New York-based Pfizer, in a statement yesterday.

“We stand behind the current, science-based guidance in Prempro’s label, which advises doctors to prescribe the medicine at the lowest effective dose and for the shortest duration,” Loder said. Women should talk to their doctors about how long they should be on the therapy, he said.

Prempro is a combination of hormones used to replace those that the body stops making when a women enters menopause, triggering symptoms like hot flashes and mood swings. It is made up of Premarin, an estrogen gathered from the urine of pregnant horses, and progestin that reduces the risk of uterine cancer linked to the use of estrogen alone.

The two products generated $260 million for Pfizer in the second quarter of 2010.

Declining Rates

The decline in hormone use after the Women’s Health Initiative results were initially released led to a drop in breast cancer rates, with about 100,000 fewer invasive tumors detected from 2002 to 2007 than expected, said Chlebowski, chief of medical oncology at the University of California, Los Angeles, School of Medicine. With a 10-year mortality rate of about 20 percent, the reduction in hormone use may have prevented about 20,000 deaths, he said.

It is likely that the risk of dying from breast cancer was underestimated and will increase with time, wrote Peter Bach, from Memorial Sloan-Kettering Cancer Center’s health outcomes research group, in an editorial accompanying the study. While many physicians and women may believe brief periods of hormone therapy is safe, more study is needed to prove that, he said.

“Given the substantial population of women who seek relief from menopausal symptoms and the large potential burden of disease that could be created if medications given to alleviate symptoms today cause cancer and other deaths tomorrow, it seems that additional randomized trials are needed,” Bach wrote.

Pfizer’s Lawsuits

Pfizer is facing about 8,000 lawsuits seeking millions of dollars in damages over sales of Prempro and Premarin.

Some verdicts against Pfizer’s Wyeth unit were thrown out at the post-trial stage or damages were reduced. The company also has won dismissals of more than 3,000 cases before trial, according to court filings. A jury yesterday found Pfizer properly warned an Arkansas woman about the cancer risks of Prempro and rejected her claim for at least $3.5 million in damages.

The health initiative stopped giving women hormones in 2002, while continuing to track them, providing the investigators with the largest group of 80-year-old and 90-year-old women in the world, Chlebowski said. The study is funded by the U.S. National Institutes of Health.

The breast cancer deaths in women on hormone replacement therapy add to findings in the journal Lancet last year that the pills also raise the risk of dying from lung cancer. Women taking the pills may want to consider a respite to see if they still need the medicine, Chlebowski said. While U.S. regulators recommended hormones be used at the lowest dose for the shortest time possible, many women don’t try to stop them, he said.

“You really don’t want to be taking a medication that increases the two leading causes of cancer death in women, unless you really have to,” Chlebowski said.

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