A recent study found that a drug called ibandronate successfully reduced the number of breast cancer cells in the bones of mice. Ibandronate belongs to a class of drugs called bisphosphonates that scientists have been studying to determine whether they can block the progression of breast cancer cells that have spread to the bone. 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. With these advances in research, the American Society of Clinical Oncology (ASCO) recently published guidelines on the role of bisphosphonates in breast cancer.
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).
According to an expert panel of the American Society of Clinical Oncology (ASCO), bisphosphonates have shown benefits in reducing bone complications. However, bisphosphonates have not had an impact on patient survival (i.e., patients do not live longer if they take bisphosphonates). Thus, bisphosphonates are used to improve a patient’s quality of life rather than cure the disease. While bisphosphonates can be helpful, the ASCO believes they should not replace current standards of treatment for cancer pain, such as local radiation therapy and other medications.
In addition to treating bone metastases, bisphosphonates are also being studied to see if they can play a role in the prevention of metastatic breast cancer (breast cancer that has spread to other organs, such as the bone, liver, lung, etc.). Some bisphosphonates, such as Fosamax (generic name, alendronate), are already used to treat osteoporosis, a degenerative bone disease primarily affecting post-menopausal women.
Currently, Aredia is the only FDA-approved bisphosphonate to treat breast cancer patients with bone metastases. Aredia is administered intravenously (through a vein) along with other cancer treatments, such as chemotherapy. Clinical studies have shown that breast cancer patients with bone metastases who are given Aredia tend to experience a delay in or reduction of bone pain, fractures, and other bone complications compared to patients who do not receive Aredia. Possible side effects of Aredia include fever, fatigue, nausea and vomiting, initial bone pain, lack of appetite, and anemia (decrease in red blood cells).
Other bisphosphonates have also shown promise in alleviating symptoms of bone metastases. In the most recent study on bisphosphonates, ibandronate stopped the progression of bone metastases in mice and halted the formation of new metastases. Other bisphosphonates under investigation for treating bone metastases include:
- Didronel (generic name, etidronate)
- Bonefos, Clostoban, Loron, Ostac (generic name, clodronate)
- Skelid (generic name, tiludronate)
- Fosamax (generic name, alendronate)
- Zometa (generic name, zoledronate)
At this time, most physicians do not see sufficient evidence to recommend bisphosphonates for breast cancer patients who do not already have bone metastases.
Advanced, or metastatic, breast cancer describes a cancer that has spread from the breast to distant organs in the body. After the axillary lymph nodes, breast cancer most often spreads first to the bone. The lungs and liver are other common sites that breast cancer affects. Treatment of metastatic breast cancer generally focuses on relieving symptoms and extending a woman’s lifetime. The National Cancer Institute estimates that approximately 10% to 20% of women with metastatic breast cancer survive the disease. According to the ASCO, the average breast cancer patient whose cancer has spread only to the bone survives 36 months compared to an average of 18 to 24 months for breast cancer patients whose cancer has spread to other regions of the body, such as the liver, lung, brain, etc.
The chances of successful treatment and survival of breast cancer are much greater when the cancer is detected and treated before it has spread beyond the breast. Therefore, all women should follow the guidelines for early breast cancer detection:
- All women between 20 and 39 years of age should practice monthly breast self-exams and have physician performed clinical breast exams at least every three years.
- All women 40 years of age and older should have annual screening mammograms, practice monthly breast self-exams, and have yearly clinical breast exams. The clinical breast exam should be conducted close to and preferably before the scheduled mammogram.
- Younger women with a family or personal history of breast cancer should talk to their physicians about beginning annual mammograms before age 40.
- The study, "The Bisphosphonate Ibandronte Promotes Apoptosis in MDA-MB-231 Human
Breast Cancer Cells in Bone Metastases," is published in the June 2001 issue of Cancer
Research. An abstract of the study is available at http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd
=Retrieve&db=PubMed&list_uids=11389070&dopt=Abstract - The American Society of Clinical Oncology published a 1999 article on bisphosphonates entitled, "American Society of Clinical Oncology Guideline on the Role of Bisphosphonates in Breast Cancer." The article is available at http://www.asco.org/prof/pp/html/guide/bisph/m_bisph-intro.htm
- To learn more about bisphosphonates for the treatment of osteoporosis, please visit http://www.imaginis.com/osteoporosis/osteo_treatment.asp
- To learn more about other drugs used to treat breast cancer, please visit http://www.imaginis.com/breasthealth/drugs.asp
- To learn more about advanced (metastatic) breast cancer, please visit http://www.imaginis.com/breasthealth/metastatic.asp
