SAN ANTONIO - One of the most promising new approaches for fighting breast cancer was set back Thursday when a major study showed that a bone-building drug did not stop cancer from returning or extend life for most women fighting it.

However, the drug Zometa did seem to help certain postmenopausal women. Its maker, Novartis AG, is considering further study, but will suspend plans to expand it beyond its current use as a treatment for patients whose cancer has spread to the bone.

"Ten years of work and to have essentially a negative study is disappointing, particularly on a tremendous wave of enthusiasm for this based on some positive trials in the past," said the study's leader, Robert Coleman of the University of Sheffield, England. He presented results at a conference in San Antonio.

Bone drugs called bisphosphonates, sold as Fosamax, Boniva, and Actonel, have long been sold for treating osteoporosis. Those are daily pills; Zometa, sold as Reclast for osteoporosis, is given as an infusion twice a year.

Hopes that these drugs could also prevent cancer soared after a study two years ago found Zometa cut the risk of cancer recurrence by 30 percent in younger women forced into early menopause by hormone treatments they received.

The excitement grew last year, when a large study found that women who were not cancer patients and were taking daily bisphosphonate to prevent bone problems were about one-third less likely to develop breast cancer.

The new study was meant to be definitive. It tested Zometa in 3,360 women of all ages in seven countries who had breast cancer that had spread to lymph nodes. All received standard cancer treatments; half also got infusions of Zometa for five years.

After five years, about 400 women in each group had died or suffered a recurrence.

Among the 1,100 women who were at least five years past menopause when the study began, however, Zometa cut the risk of recurrence by 27 percent and improved survival odds by 29 percent.

Side effects are a concern: 26 women on Zometa - 1 to 2 percent of the group - developed confirmed or suspected cases of jawbone decay, a serious problem long linked to bisphosphonates. Blood clots in the lung were more common, though not significantly so.