Practical guidance for the management of aromatase inhibitor-associated bone loss

Background: Recent studies indicate that women with breast cancer are at increased risk of fracture compared with their age-matched peers. Current treatment guidelines are inadequate for averting fractures in osteopenic women, especially those receiving aromatase inhibitor (AI) therapy. Therefore, we sought to identify clinically relevant risk factors for fracture that can be used to assess overall fracture risk and to provide practical guidance for preventing and treating bone loss in women with breast cancer receiving AI therapy. Methods: Systematic review of pertinent information from published literature and meeting abstracts through December 2007 was carried out to identify factors contributing to fracture risk in women with breast cancer. An evidence-based medicine approach was used to select risk factors that can be used to determine when to initiate bisphosphonate treatment of aromatase inhibitor-associated bone loss (AIBL). Results: Fracture risk factors were chosen from large, well-designed, controlled, population-based trials in postmenopausal women. Evidence from multiple prospective clinical trials in women with breast cancer was used to validate AI therapy as a fracture risk factor. Overall, eight fracture risk factors were validated in women with breast cancer: AI therapy, T-score <-1.5, age >65 years, low body mass index (BMI <20 kg/m²), family history of hip fracture, personal history of fragility fracture after age 50, oral corticosteroid use >6 months, and smoking. Treatment recommendations were derived from randomized clinical trials. Conclusions: The authors recommend the following for preventing and treating AIBL in women with breast cancer. All patients initiating AI therapy should receive calcium and vitamin D supplements. Any patient initiating or receiving AI therapy with a T-score ≥-2.0 and no additional risk factors should be monitored every 1-2 years for change in risk status and bone mineral density (BMD). Any patient initiating or receiving AI therapy with a T-score <-2.0 should receive bisphosphonate therapy. Any patient initiating or receiving AI therapy with any two of the following risk factors - T-score <-1.5, age >65 years, low BMI (<20 kg/m²), family history of hip fracture, personal history of fragility fracture after age 50, oral corticosteroid use >6 months, and smoking-should receive bisphosphonate therapy. BMD should be monitored every 2 years, and treatment should continue for at least 2 years and possibly for as long as AI therapy is continued. To date, the overwhelming majority of clinical evidence supports zoledronic acid 4 mg every 6 months to prevent bone loss in women at high risk. Although there is a trend towards fewer fractures with zoledronic acid, studies completed to date have not been designed to capture significant differences in fracture rate, and longer follow-up is needed.