Chicago A drug to prevent bone loss during breast cancer treatment also substantially cut the risk that the cancer would return, results that left doctors excited about a possible new way to fight the disease.
It is the first large study to affirm wider anti-cancer hopes for Zometa and other bone-building drugs called bisphosphonates. Zometa, made by Novartis AG, is used now for cancers that have already spread to the bone.
The new study involved 1,800 premenopausal women taking hormone treatments for early-stage breast cancer. Zometa cut by one-third the chances that cancer would recur - in their bones or anywhere else.
"This is an important finding. It may well change practice," said Dr. Claudine Isaacs, director of the clinical breast cancer program at Georgetown University's Lombardi Cancer Center.
About three-fourths of breast cancers occur in women after menopause. Zometa may help them, too, but it hasn't been tested yet in that age group.
The study was led by Dr. Michael Gnant of the Medical University of Vienna and reported Saturday at an American Society of Clinical Oncology conference in Chicago.
If a second, ongoing study also finds a benefit, doctors predict that Zometa will quickly be tested against other cancers that tend to spread, or metastasize, to bones, such as prostate and kidney cancer.
"Hugely important is whether this has to do with the fact that it just makes the bone hostile, somehow, to metastasis or if there is a more global anti-metastasis effect," said the oncology group's president, Dr. Nancy Davidson of Johns Hopkins University.
"Either of those would be good and would teach us a lot about what to do next."
Breast cancer is the most common cancer in women. About 184,450 cases and 40,930 deaths from the disease are expected in the U.S. this year.
Standard treatments are surgery, chemotherapy, radiation and hormone-blocking drugs if the tumors are like those in the study - helped to grow by estrogen or progesterone.
The hormone-blockers often weaken bones, so bisphosphonates like the osteoporosis pill Fosamax have become increasingly popular to treat this side effect. However, using them to treat the cancer itself is a very different approach.
Lab studies hinted it would work, and Gnant's is the first to test it in a large group of breast cancer patients.
All had surgery to remove their tumors and were taking hormone-blocking drugs - goserelin plus either tamoxifen or anastrozole - treatments that made them menopausal. Half also were given infusions of Zometa once every six months.
The women were treated for three years and studied for two more. By then, only 6 percent of those given Zometa had suffered a relapse or died, compared to 9 percent of the others. That translated to a 36 percent decline in risk.
Sixteen women given Zometa died versus 26 of the others - a difference that could have occurred by chance alone but an encouraging trend that doctors hope will mean better survival as the groups are followed for a longer time.
There were no big differences in serious side effects, though minor ones like fever and bone and joint pain were more common among women given Zometa. Two percent of all study participants developed a rapid heartbeat, but only three were hospitalized - two on Zometa and one of the others.