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A drug called clodronate (brand names, Bonefos, Clostoban, Loron, Ostac) may reduce the
chances that breast cancer will spread to the bone, according to new research presented at
the annual meeting of the American Society for Bone and Mineral Research in San Antonio.
Clondronate belongs to a class of drugs called bisphosphonates, many of which are being
investigated for use in breast cancer patients. In addition to preventing the spread of
breast cancer to the bone, patients who were given clondronate in the study were also less
likely to die of breast cancer, compared to women who were given a placebo, an inactive
pill.
When breast cancer spreads past the breast and axillary (armpit) lymph nodes, it often spreads first to the bone. These
breast cancer tumors in the bone are called "bone metastases." As advanced
breast cancer dissolves portions of bone, a variety of problems can occur. Bone metastases
can cause pain, decreased activity, and potentially severe problems such as fractures.
Other complications that can arise from bone metastases include the surgical treatment for
fractures, hypercalcemia (abnormally high levels of calcium), and spinal cord compression
(vertebral damage due to pressure on the spinal cord).
A group of drugs called bisphosphonates are currently used to help treat osteoporosis,
a degenerative bone disease affecting mainly post-menopausal women. In patients with
osteoporosis, the bone loses a significant portion of its density, greatly increasing the
risk of serious fractures. One bisphosphonate, Aredia (genetic name, pamidronate
disodium), has already been approved by the U.S. Food and Drug Administration (FDA) to
help treat bone metastases caused by breast cancer while a number of other bisphosphonates
are currently under investigation for this use.
Dr. Eugene McCloskey, Sr. of the University of Sheffield in Sheffield, England and his
colleagues enrolled 1,069 women who had been diagnosed with breast cancer between 1989 and
1995. All of the women received surgery, radiation,
chemotherapy and the anti-cancer drug tamoxifen as required. Then, Dr. McCloskey and his team
randomly assigned some of the women in the study to receive 1,600 milligrams of
clondronate each day six months into their treatment for a period of two years. The
remaining women were given a placebo—an inactive pill.
The women were watched for a total of five years, during which time there was a
non-significant decrease in the incidence of bone metastases among the women who were
given clondronate. However, when the researchers analyzed only the two year medication
period when the women were actively taking clondronate, they found that the drug did
significantly reduce the number of bone metastases: 12 women developed bone metastases in
the clodronate group compared with 28 women in the placebo group.
Furthermore, when evaluating the women over five years, Dr. McCloskey and his
colleagues found a reduction in the number of deaths from breast cancer among the women
who were given clondronate: 98 women on clondronate died from breast cancer versus 129
women who were given a placebo.
Other bisphosphonates under investigation for treating bone metastases include:
- Didronel (generic name, etidronate)
- Skelid (generic name, tiludronate)
- Fosamax (generic name, alendronate)
- Zometa (generic name, zoledronate)
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