Researchers from Toronto, Canada, recently reported that switching to a different bisphosphonate significantly improves pain control in women with worsening bone metastases from breast cancer who are already being treated with a bisphosphonate. These results were recently presented at the 28th San Antonio Breast Cancer Symposium (SABCS).
As breast cancer becomes more advanced, it tends to spread throughout the body; the bones are a common site of spread. Spread of cancer to the bone from its original site is referred to as bone metastasis. Bone metastases can reduce quality of life and may ultimately cause bone pain, bone fractures, spinal compression, or abnormal calcium levels in the blood.
Bisphosphonates are a class of drugs used for the treatment of cancer-related hypercalcemia (high levels of calcium in the blood) and of bone metastases in patients with advanced cancers. Bisphosphonates decrease the rate of bone destruction in patients with bone metastases. Clinical studies have also demonstrated that bisphosphonates can significantly decrease the pain and number of fractures resulting from bone metastases.
When a breast cancer patient with bone metastases experiences a worsening of the metastases, she is often prescribed a different hormone and/or chemotherapy regimen. The effect of switching to a different bisphosphonate, however, has not been explored.
Researchers from Canada conducted a study to evaluate the effect of switching to a new bisphosphonate in 31 in women with worsening bone metastases. The women were originally taking the bisphosphonate drugs clodronate or pamidronate. They were switched to Zometa® (zoledronic acid). The women had no other changes in systemic therapy in the month before or after the start of the study.
- Eight weeks after changing to Zometa, improvements in pain control were noted by roughly 42% of patients.
- Improvements in markers of bone turnover also occurred during this time period.
The researchers concluded that switching to a different type of bisphosphonate appears to be a reasonable treatment approach for women with worsening bone metastases who are already being treated with a bisphosphonate. This was the first prospective study to demonstrate that patients can receive significant symptom relief by switching from clodronate or pamidronate to Zometa upon worsening of bone metastases. If confirmed in randomized trials, these results may have major implications for the treatment of bone metastases in women with breast cancer.
Reference: Clemons M, Dranitsaris G, Ooi W, et al. A phase II trial Evaluating The Palliative Benefit of Second-Line Zoledronic Acid in Breast Cancer Patients with Either a Skeletal Related Event (SRE) or Progressive Bone Metastases (BM) Despite Standard Bisphosphonate (BP) Therapy. Proceedings from the 28th San Antonio Breast Cancer Symposium. December 8-11, 2005. Abstract #1122.