Cancer cells have the ability to spread from their original location to other parts of the body. Researchers at the Washington University School of Medicine in St. Louis believe a bone-strengthening drug may help limit the spread of breast cancer.
Cancer tumors regularly shed thousands of cells that can travel to other parts of the body. These cells are called disseminated tumor cells or DTCs. In the case of breast cancer, DTCs have a strong tendency to travel into the bone marrow. Growth factors in the marrow that help the body produce new bone seem to help the cancer cells survive inside the marrow. As the marrow produces blood, the cancer cells can be sent out into other parts of the body where they cause new tumors that are a leading cause of death.
Chemotherapy is the use of special chemicals or drugs to kill off cancer cells. Chemotherapy or chemo is commonly used along with surgery to treat breast cancer. But chemotherapy can also increase the rate that the body produces new bone, which means the amount of bone growth factors in the body become higher during chemo treatments. So at the same time the chemo is killing the tumor, the growth factors in the bone marrow are helping preserve stray cancer cells that can come back later.
To help preserve bone during chemotherapy, the bone-strengthening drug zoledronic acid, which is sold under the brand name Zometa, is sometimes prescribed along with chemotherapy. In the past, zoledronic acid was commonly combined with chemotherapy treatments after surgery was done to remove breast cancer tumors. Researchers at Washington University suggested that this drug can help prevent DTCs from surviving in the bone marrow when the drug is combined with chemo treatments and estrogen-lowering therapy before surgery.
The study followed 109 women with newly diagnosed stage II or stage III breast cancer. Half of the patients received chemotherapy alone, while the other half received both chemo and zoledronic acid. Three months later, the number of breast cancer cells in the bone marrow dropped from 43 percent to 30 percent for patients who received the drug combination as compared to a decrease of only one percentage point for patients in the other group. Even more significantly, of the patients who had no DTCs in their bone marrow before treatment, 87 percent were still free from DTCs in the marrow after three months of the combined drugs. Only 60 percent of patients who just received chemo remained free from DTCs in the marrow.
Another concern for chemotherapy patients is loss of bone density. Many women develop osteoporosis as a result of chemo treatments. This study showed that the patients who received both chemo and zoledronic acid actually had significant gains in bone density after 12 months. Yet another potential benefit of the drug combination appears to be a direct impact on some breast cancer tumors. Researchers believe zoledronic acid helps keep the tumor from creating the blood supply it needs to grow. The drug may also modify the immune system to make it harder for tumor cells to survive, and it may even trigger some cancer cells to self-destruct.
Researchers in this study are recommending further study at a larger facility. They believe their results show that women would benefit from the combination of chemo and zoledronic acid prior to surgery whenever chemo is given.