Taxol, a widely used chemotherapy drug, is useless in treating the most common form of breast cancer and helps far fewer patients than previously believed, said a study in Thursday's New England Journal of Medicine.

The study reanalyzed a research done in the 1990s, using modern genetic tools that were not available at that time.

"The days of 'one size fits all' therapy for patients with breast cancer are coming to an end," Dr. Anne Moore of Weill Cornell Medical College wrote in an editorial in the journal.

In the study, paclitaxel, sold as Taxol by New York-based Bristol-Myers Squibb Co. , did the most good for women who had overactive HER-2 genes. These women were about 40 percent less likely to have a recurrence if they received Taxol.

However, the drug did not significantly help women whose tumors were HER-2 negative and were being helped to grow by estrogen. This is the most common form of the disease.

If further study provides the same results, over 20,000 women each year in the United States alone might be spared the side effects of this drug or similar ones without significantly raising the risk their cancer will return.

That would be roughly half of all breast cancer patients who get chemo now.

"We want to make sure these data are correct before withholding it (Taxol) from some patients ... the stakes are high," said the lead researcher, Dr. Daniel Hayes of the University of Michigan. "On the other hand, we don't want to keep a therapy that doesn't work."

The new study was funded by the federal government and a breast cancer foundation. Several researchers consult for Bristol-Myers Squibb.

"We should have done this a long time ago, but the tools were lacking and researchers now have the advantage of longer follow-up of these women," said co-author, Donald Berry of the University of Texas M.D. Anderson Cancer Center.

Berry was reanalyzing another earlier Taxol study, and Moore urged other scientists to do the same.

With more evidence, "we can begin to use the biology of the cancer to decide whether the chemotherapy will work" before subjecting women to it, Hayes said.

(Agencies via Xinhua News Agency October 11, 2007)