WEDNESDAY, Dec. 7 (HealthDay News) -- A drug developed to treat osteoporosis appears to boost survival in women with certain types of breast cancer, according to two new studies.

These preliminary findings regarding the bone-building drug zoledronic acid potentially give scores of women more options to battle their tumors. The studies are slated for presentation at the San Antonio Breast Cancer Symposium this week.

The first looked at premenopausal women with estrogen receptor-positive breast cancer receiving either the bone drug plus hormone therapy or a placebo plus hormone therapy for three years.

Earlier data from this study were encouraging, and this update -- 84 months after the trial's start -- provides further evidence of improved disease-free survival and recurrence rates among women receiving zoledronic acid. The drug is known by the brand names Reclast and Zometa.

The new research shows that women receiving zoledronic acid had a 28 percent reduced risk for recurrence and a 36 percent reduced risk for dying.

Women over the age of 40 received the most benefit, the researchers said.

"In general, the overall survival is excellent, which demonstrates that treating these patients without adjuvant chemotherapy is a very good approach," said study author Dr. Michael Gnant, a professor of surgery at the Medical University of Vienna, Austria. He said the study received academic and not pharmaceutical funding.

Many women were still seeing the benefit four and five years after their treatment stopped. "This means we've changed something in the beginning in terms of the disease," Gnant said.

Cancer patients often take bone-building drugs, commonly referred to as bisphosphonates, to prevent fractures related to spread of the cancer to the bone. But zoledronic acid is not an approved treatment for breast cancer in many countries, including the United States, which makes its availability uncertain, Gnant noted.

In another study, postmenopausal women who received zoledronic acid plus an aromatase inhibitor (a type of hormone therapy) had a 29 percent lower risk for a recurrence and a 35 percent improvement in survival vs. women receiving zoledronic acid plus a placebo.

The drug also appeared to increase bone mineral density.

"We've been waiting for these data," said Dr. Jane Carleton, an oncologist with Monter Cancer Center in Lake Success, N.Y. "Not only did it just prevent bone loss, it decreases the chances of the cancer coming back. That's powerful."

A third study of bisphosphonates found that the drug clodronate reduced the likelihood of cancer spreading in postmenopausal women by about 9 percent, less than was hoped for.

Slightly more encouraging were reductions in mortality (16 percent). Clodronate is known by the brand name Bonefos.

The trial was partially supported by Bayer Schering Pharma Oy, which makes Bonefos.

A final study had disappointing results for patients receiving high-dose chemotherapy and another bisphosphonate, ibandronate (Boniva).

The drug did not improve either time to a recurrence or overall survival in women already treated with chemotherapy.

Other trials had shown more positive results.

Research presented at meetings should be considered preliminary until published in a peer-reviewed medical journal.

More information

The U.S. National Cancer Institute has more on breast cancer treatments.