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Aromasin May Cut Breast Cancer Return

Study Shows Switching to Aromasin After Tamoxifen Therapy Cuts Risk of Cancer Coming Back
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WebMD Health News

Dec. 15, 2006 (San Antonio) -- The breast cancer drug Aromasin cuts the risk of breast cancer recurrence by about one-third in postmenopausal women previously treated with tamoxifen, researchers report.

Only 9% of women given Aromasin -- after completing tamoxifen treatment -- suffered a recurrence, compared with 11% of those given placebo, says researcher Terry Mamounas, MD, associate professor of surgery at Northeastern Ohio Universities College of Medicine in Canton.

"Previous research showed a clear benefit for women who receive Aromasin after two to three years of tamoxifen," he tells WebMD. "The new findings show that Aromasin is also effective after five years of tamoxifen."

The study, presented at the San Antonio Breast Cancer Symposium, included nearly 1,500 postmenopausal women who after five years of taking tamoxifen were followed for the next 30 months.

How the Drugs Work

About 70% of women with breast cancer have tumors that are fueled by estrogen, making hormone therapy a cornerstone of regimens to prevent recurrences and improve survival.

For more than 25 years, doctors have been using tamoxifen (an antiestrogen) to deprive breast cancer cells of the estrogen which they need to grow. But after five years of treatment, the benefits of tamoxifen decrease.

Newer drugs known as aromatase inhibitors, such as Aromasin, block an enzyme the body uses to make estrogen, slashing the body's production of estrogen and depriving hormone-receptor-positive breast cancer cells.

Studies over the past five years have consistently shown that aromatase inhibitors shrink tumors better with fewer side effects, Mamounas says.

Treatment Options

Aromasin isn't the first aromatase inhibitor to benefit women who complete tamoxifen treatment.

In 2003, a landmark trial was halted prematurely when Femara, given after tamoxifen therapy, was shown to result in a lower breast cancer recurrence rate when compared with women who do not take Femara after tamoxifen. Now Femara is routinely offered to such women.

The new findings show that women have two options after five years of tamoxifen therapy, Mamounas says.

That's important because some women can't tolerate one drug or the other, says Kathy Albain, MD, a breast cancer specialist at Loyola University of Chicago Medical Center who was not involved with the work.

Femara remains the standard of care after five years of tamoxifen, she says, as it was tested in a more robust, larger, and longer study.

"These data give us some confidence that we can give Aromasin to these patients and still achieve good results," Albain tells WebMD.

Aromasin Side Effects

Results of the new trial showed that certain groups of women particularly benefited from Aromasin therapy, including those younger than 60, those with small tumors (less than 2 centimeters in diameter), and those who received previous chemotherapy.

The drug was generally well tolerated, but women taking Aromasin had side effects related to the drops in estrogen that are consistent with the effects of the drug including joint pain, bone pain, and fatigue.

While the researchers note that estrogen-depleting drugs, including aromatase inhibitors, have been linked to an increased risk of osteoporosis and bone problems, similar numbers of women in both groups experienced fractures.

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