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Drug Cuts Risk Of Some Breast Cancers

June 5, 2011

Researchers at Massachusetts General Hospital announced Saturday they found that an estrogen-blocker known as Aromasin reduces the risk of developing breast cancer by 65 percent in post-menopausal women at high risk for breast cancer.

In a late-stage trial of more than 4,500 post-menopausal women who were at increased risk of developing breast cancer, researchers found that those who took the drug, also known as exemestane, had fewer invasive breast cancers after 3 years and without severe side effects.

“We are delighted with this two-thirds reduction,” Dr. Paul Goss, director of Breast Cancer Research at Massachusetts General Hospital, told Reuters in an interview, noting that there were fewer of the more aggressive types of tumors in patients who took the drug, but the limitation of the study was that the median follow-up was just 3 years.

The study results were presented at an annual meeting of the American Society of Clinical Oncology in Chicago.

The study, sponsored by Pfizer, broke participants up into two groups. The first group got the drug while the second group received a placebo. Eleven invasive breast cancers were reported in the drug group compared to 32 in the placebo group. There were also fewer cases of precursor lesions in the drug group.

Study-leader Goss said that tamoxifen has been used for years to prevent breast cancer, but not without serious side effects. Exemestane, however, did not cause high levels of toxicity, he noted. Its side effects were much milder that those seen with tamoxifen, although there was a slight increase in osteopenia (low bone density), but not low enough to be classified as osteoporosis.

Other side effects reported in the study included hot flashes, sweating, fatigue, and insomnia.

“Age is the single biggest risk factor for developing breast cancer. Once you are 60, your risk increases so this (research) merits consideration for prevention. What we don’t know is whether patients need to take this pill for life,” said Goss.

After 5 years, there was no dangerous accumulation of toxicity from the drug, he said.

“I can’t look someone in the eye and swear it won’t be (toxic over a longer period of time), but there’s large evidence that the drug is safe,” he told Reuters.

And the price of exemestane has fallen greatly, mainly due to the fact that the drug, sold by Pfizer under the brand name Aromasin, lost its patent April 1, 2011, allowing for cheaper generic versions of the drug to be produced.

Dr. Andrew Seidman, an oncologist at New York’s Memorial Sloan-Kettering Cancer Center, called the study results exciting because exemestane gives high-risk women an alternative to tamoxifen and to a double mastectomy just to prevent getting the disease.

Goss said he wondered whether will now try to extend its patent on Aromasin based on the new findings.

A spokesman for Pfizer declined to comment on the drugmaker’s plans. “What we can say is that the ongoing evaluation of Aromasin by the research community contributes to a growing body of knowledge in breast cancer and may help clinicians and patients determine the best use of aromatase inhibitor therapy,” the spokesman said.

An estimated 1.3 million women are diagnosed with breast cancer worldwide each year and nearly 500,000 die of the disease. It is the second leading cause of cancer death among U.S. women after lung cancer.

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