Analysis of skeletal-related events in breast cancer and response to therapy

The skeleton is a common site for the spread of metastatic cancer and skeletal complications are a cause of significant morbidity and mortality. Treatment of skeletal morbidity is therefore an essential component of therapy for cancer patients with bone metastases. Bisphosphonates are currently the treatment of choice for skeletal complications. In a patient diagnosed with bone metastases, skeletal morbidity is evaluated by a number of endpoints known as skeletal related events. These include bone pain, requirement for radiation or surgery to bone, pathologic and radiologic fractures, hypercalcemia, and progression of bone metastases. The efficacy of bisphosphonate treatment is evaluated by their effect on the number and frequency of skeletal-related events. In addition, surrogate markers of bone resorption such as collagen telopeptides or quality of life measurements can be used to monitor therapy, though these do not necessarily reflect skeletal morbidity. Intravenous pamidronate is currently the standard treatment for patients with bone metastases, and is effective in reducing the frequency of a variety of skeletal-related events. The more potent bisphosphonates ibandronate and zoledronate are now being evaluated in this setting. These agents may offer advantages over pamidronate in terms of convenience of administration. Clinical trials underway will determine whether they are equivalent or even superior to pamidronate in reducing skeletal-related events.