A new type of drug shows growing promise as a more potent way for many breast-cancer patients to significantly cut their risk of recurrence, researchers reported yesterday. The latest findings from...

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A new type of drug shows growing promise as a more potent way for many breast-cancer patients to significantly cut their risk of recurrence, researchers reported yesterday.

The latest findings from a large international study also found that the drug, an aromatase inhibitor known generically as anastrozole, appears to sharply reduce the chances that many breast-cancer patients will develop cancer in the other breast or have the cancer spread.

The results were so strong that researchers recommended that most postmenopausal women struck by breast cancer should immediately begin taking an aromatase inhibitor as soon as they complete the standard regimen of surgery, radiation and, often, chemotherapy, instead of first going on an older drug.

Other experts praised the findings as confirming that aromatase inhibitors should play an important role in treating breast-cancer patients but said it remains unclear whether all eligible women should immediately begin an aromatase inhibitor. Some patients might still first try the older drug, tamoxifen, they said.

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“This is a very large study and it confirms there is a benefit and that aromatase inhibitors should become part of standard therapy,” said JoAnne Zujewski of the National Cancer Institute. “But the exact timing of how one should use them remains unclear.”

Before the development of aromatase inhibitors, women whose breast cancers were promoted by the hormone estrogen — which is true of most — were given tamoxifen to reduce their risk of recurrence. Tamoxifen blunts estrogen’s effects. But tamoxifen can be taken only for five years and increases the risk of uterine cancer and blood clots that can cause strokes.

Aromatase inhibitors block the formation of estrogen in the first place and carry none of those risks. They do not, however, reduce the risk of osteoporosis, as tamoxifen does, and joint pain is more common than among women taking tamoxifen.

But it has been unclear whether women should take tamoxifen first and switch to an aromatase inhibitor or take an aromatase inhibitor from the start.

The new findings are from a study involving 9,366 postmenopausal women with early, estrogen-sensitive breast cancer who took either tamoxifen or anastrozole, trade name Arimidex.

The researchers had previously reported data from three years of study that showed Arimidex prevented more recurrences than tamoxifen. The new data found the benefits continued after five years and appeared to be even greater, the researchers said. Tamoxifen cut the recurrence risk by about 50 percent; Arimidex appeared to reduce recurrence by an extra 26 percent, the researchers said.

“We think women should start right away with an aromatase inhibitor,” said Anthony Howell of the Christie Hospital in Manchester, England, who presented the findings at a meeting in San Antonio, Texas. “We think the benefit justifies offering this treatment as early as possible.”

Other research presented at the meeting found that switching to Arimidex or another aromatase inhibitor called Aromasin was more effective than taking tamoxifen for five years.

“This data strengthens the thinking that tamoxifen is tending to die out as a treatment and is being replaced by these aromatase inhibitors,” Howell said.

But other experts said the data simply confirmed the study’s earlier findings and the results of other ongoing studies were needed before changing the standard treatment.

“I would say that these results generally provide confirmation of what was previously seen in this trial but are not strikingly different,” said Eric Winer of the Dana-Farber Cancer Institute in Boston. Winer chaired a panel for the American Society of Clinical Oncology that last month recommended that aromatase inhibitors become part of the standard arsenal of drugs used to treat breast cancer, though the exact strategy of how to use them remains unclear.

“We still should be careful not to rush to judgment as to what the best way should be to use these drugs,” Winer said.

The new study was funded by AstraZeneca, which makes Arimidex and Nolvadex, the trade name for tamoxifen. Howell said the researchers had complete independence, and AstraZeneca spokeswoman Mary Lynn Carver said the company’s patent for tamoxifen has expired.

Material from USA Today and Chicago Tribune is included in this report.