P104 Continuing benefit of zoledronic acid for the prevention of skeletal complications in breast cancer patients with bone metastases

Bone health management in patients with breast cancer: current standards and emerging strategies

In women who develop bone metastases from breast cancer (BC), interactions between tumor cells and osteoclasts within the bone lead to localized bone destruction and increase the risk of skeletal-related events (SREs). Bisphosphonates inhibit osteoclast-mediated bone resorption, and have been used extensively for treating post-menopausal osteoporosis and reducing the risk of SREs in patients with bone metastases. A number of clinical trials in women with early stage BC have demonstrated that adding bisphosphonates to adjuvant endocrine therapy can prevent bone loss and may prevent disease recurrence and improve disease-free survival. In women with bone metastases from BC, bisphosphonates have demonstrated efficacy for reducing skeletal morbidity and pain and improving quality of life. Recent economic analyses have demonstrated that bisphosphonate therapy is a cost-effective use of healthcare resources. This review summarizes the available data for bisphosphonate benefits in both the adjuvant and metastatic settings in the context of evolving clinical practice.

Bisphosphonates: reducing the risk of skeletal complications from bone metastasis

Women with advanced breast cancer often develop bone metastases that are associated with skeletal-related events (SREs), which reduce quality of life and increase the risk of death. Because patients who experience one SRE are more likely to experience subsequent events, the goal of therapy is to preserve quality of life by delaying the onset of the first SRE and reducing the incidence of subsequent SREs. Bisphosphonates are used for clinical management of malignant bone disease, and data suggest that early treatment (e.g., before bone pain) may confer additional clinical benefit. Furthermore, data from subsets of zoledronic acid trials suggest that long-term bisphosphonate therapy may provide sustained clinical benefit throughout the disease course. Bisphosphonates are generally safe and well tolerated; adverse events are more often mild and transient. Zoledronic acid has proven efficacy for reducing risk of SREs, and ongoing studies are under way to evaluate customized treatment schedules.

Pathologic fractures correlate with reduced survival in patients with malignant bone disease

BACKGROUND

Data from randomized, controlled trials of zoledronic acid were retrospectively analyzed to assess the effect of pathologic fractures on survival in patients with malignant bone disease.

METHODS

A Cox regression model was used to estimate the effect of fractures (time-dependent variable) on survival in patients with stage III multiple myeloma or bone metastases from solid tumors enrolled in 3 large trials. Patients were randomized to receive zoledronic acid, pamidronate, or placebo every 3-4 weeks for up to 24 months (prostate cancer, breast cancer, and multiple myeloma) or up to 21 months (lung and other solid tumors).

RESULTS

A total of 3049 patients with multiple myeloma (n = 513), breast (n = 1130), prostate (n = 640), or lung cancer or other solid tumors (n = 766) were included in this analysis. Patients with multiple myeloma had the highest fracture incidence (43%), followed by breast (35%), prostate (19%), and lung cancer (17%). In all tumor types except lung, pathologic fracture was associated with a significant increase in risk of death, and breast cancer patients had the greatest increased risk. After adjustment for baseline characteristics, including performance status and prior skeletal complications, breast cancer patients who developed a pathologic fracture on study had a significant 32% increased risk of death relative to patients without a fracture (hazard ratio = 1.32; P < .01); patients with multiple myeloma or prostate cancer had a >20% increased risk of death.

CONCLUSIONS

These results suggest that fractures are associated with increased risk of death in patients with malignant bone disease. Therefore, preventing fractures is an important goal of therapy.