Improving bone health in patients with early breast cancer by adding bisphosphonates to letrozole: the Z-ZO-E-ZO-FAST program

Abstract

Women undergoing treatment for breast cancer often have a number of pre-existing risk factors for bone loss, including existing or induced postmenopausal status. Long-term anticancer treatments may further augment this risk, inducing further bone-loss, increasing the incidence of bone fractures, associated morbidity and mortality, and healthcare costs. Long-term treatment with third-generation antiaromatase agents (AAAs) is used more and more instead of or after the selective estrogen-receptor modulator tamoxifen for the adjuvant treatment of postmenopausal women with breast cancer. These AAAs include anastrozole, letrozole, and exemestane, and all are superior to tamoxifen in both efficacy and safety. In particular, they reduce the incidence of serious adverse events such as thromboembolism and endometrial cancer that are associated with tamoxifen treatment. On the other hand, the AAAs lead to profound estrogen depletion and appear to have a pronounced effect on bone mineral density (BMD), and a significantly higher incidence of osteoporosis/osteopenia and bone fracture has been reported in some trials. Bisphosphonate therapies, including zoledronic acid (ZA), have emerged as a promising means of reducing bone loss associated with antiaromatase therapy. Several large, randomized, multicenter trials are underway to determine whether upfront or delayed ZA therapy can decrease BMD losses in patients undergoing treatment with the antiaromatase agent letrozole (Z-FAST; ZO-FAST, and E-ZO-FAST), and early results from the Zometa-Femara adjuvant synergy trial (Z-FAST) trial indicate a significant benefit of upfront ZA therapy compared with delayed ZA therapy. Forthcoming results from all these trials should determine whether ZA could be used to improve bone heath in women undergoing adjuvant therapy with AAAs for breast cancer.