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Bone-Strengthening Drug Could Curb Cancer Spread
By Marilynn Larkin
Women with stage II or III breast cancer who receive the bisphosphonate zoledronic acid (Zometa) as part of their treatment are less likely to have tumor cells in their bone marrow three months later, according to Rebecca Aft, MD, PhD, of the Washington University School of Medicine in St. Louis, who presented the findings at the 2008 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago in May.
Taken together with findings of earlier studies of Zometa and other bisphosphonates, the results suggest that “women diagnosed with breast cancer should be talking with their oncologists about the advantages of a bisphosphonate,” Aft said. “I think this is likely to become the standard of care in the future.”
Tumor cells are continually being released from the primary tumor, and scientists believe that the bone marrow harbors these cells, which may eventually evolve into metastatic disease. Exactly how this happens isn’t clear. However, Aft and other researchers believe that increased bone turnover (replacing old bone with new)—an effect of chemotherapy—creates an especially nutritive environment for tumor growth. Bisphosphonates, of which Zometa is the most potent, suppress bone turnover, making the marrow less tumor-friendly.
In the Washington University study, the investigators randomly assigned 120 women whose cancer had spread to the lymph nodes or other areas near the breast to receive either 4 milligrams of zoledronic acid intravenously every three weeks for a year, starting with their first cycle of chemotherapy, or no zoledronic acid. At the time of diagnosis, none of the women had evidence of metastatic disease on imaging tests, but about 40 percent had detectable breast cancer cells in their bone marrow.
After three months, only 30 percent of those treated with zoledronic acid had detectable tumor cells in the marrow, compared with 47 percent who did not receive the bisphosphonate. Among women without detectable tumor cells in the marrow, 87 percent of those receiving the drug remained free of tumor cells compared with 60 percent of those who did not receive it. The results support a trend in favor of bisphosphonate treatment.
Future studies comparing various bisphosphonates will help determine which ones and which dosing regimens are likely to be most effective, Aft observed.
