Breast cancer drug therapy can be limited

DENVER, Oct 19, 2005 (UPI via COMTEX) -- Most breast-cancer patients do not need to take another hormone drug after completing five years of standard tamoxifen treatment, researchers said Tuesday, in findings that could slash drug costs for thousands of women.

The study showed that 70 percent of women who now are considered candidates for additional therapy with the newer hormone drugs known as aromatase inhibitors actually do not need the drugs, said researcher Dr. Gary Freedman, a radiation oncologist at Fox Chase Cancer Center in Philadelphia.

Aromatase inhibitors, which block an enzyme the body uses to make estrogen -- thereby slashing the body's production of estrogen -- include Novartis's Femara, AstraZeneca's Arimidex and Pfizer's Aromasin.

Freedman said many doctors have begun routinely prescribing aromatase inhibitors to women who complete five years of tamoxifen treatment, in light of recent findings that showed the aromatase inhibitor Femara can cut their risk of breast cancer recurrence in half.

"These drugs are very expensive and there is a large co-payment even if you have insurance," he said. "There is a very real cost issue that is not inconsequential. Plus there are side effects, chiefly an increased risk of (bone) fractures.

Freedman presented his findings at the annual meeting of the American Society for Therapeutic Radiology and Oncology.

"Is it worth it for all women who complete five years of tamoxifen to take these drugs? Our analysis suggests that at least for low-risk women, it may not be," he told United Press International.

The study included 471 women who had shown no signs of breast cancer after five years of tamoxifen treatment. Before starting tamoxifen, all of the women received breast-conserving surgery, removal of affected lymph nodes and radiation. None were given an aromatase inhibitor.

By an average of eight years later, cancer returned in 26 of the women, and another 10 developed tumors in their originally unaffected breasts.

Based on these numbers, the researchers calculated that 100 women would have to be treated to prevent one to two relapses -- a tradeoff Freedman said generally was considered too small, given the risks and costs of aromatase inhibitors.

"In clinical practice, a benefit of at least (three in 100) is commonly used to select patients for chemotherapy," he said, adding there were subgroups of women for whom the benefits did exceed the drawbacks.

Women who had not yet reached menopause, who were younger than age 60, or whose cancer had spread to four or more lymph nodes at the time they started tamoxifen, gained the most from an aromatase inhibitor, he explained. Both younger age and spread to four or more lymph nodes are risk factors for recurrence; together they accounted for about 30 percent of the women studied.

On the flip side, women over 60 who have other health conditions probably would not benefit from the drugs, Freedman said.

The study showed many of the women died from causes other than breast cancer in the 10 years after beginning tamoxifen, he said, so "whether or not they took an aromatase inhibitor would have had no impact on their survival."

Dr. Richard Poetter, a radiation oncologist at the University Clinic for Radiotherapy and Radiobology in Vienna, Austria, said given the side effects and cost of any treatment, it is a good idea to try to tease out exactly which patients will benefit most and who might not have as much to gain.

Until the new findings are confirmed, however, all eligible women who complete five years of tamoxifen therapy should discuss the risks and benefits of aromatase inhibitors with their doctors, Poetter said.

Charlene Laino covers medical research for UPI. E-mail: healthbiz@upi.com

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Copyright 2005 by United Press International