Evaluating Bone Mass and Bone Quality in Patients with Breast Cancer

Bone remodeling is a process by which bone renews itself focally in distinct areas on cancellous (ie, trabecular) bone and/or in the Haversian systems of cortical (or compact) bone. Normal bone turnover involves the ordered metabolism of bone-resorbing cells (osteoclasts) and bone-forming cells (osteoblasts). Estrogen exerts a multitude of actions on bone tissues and is integral to bone health, and estrogen deprivation leads to accelerated bone loss. Bone strength reflects the integration of bone density and bone quality. Methods to assess bone strength fall into 3 categories: radiologic (ie, bone mineral density [BMD]), biochemical (ie, markers of bone turnover), and histologic (ie, bone biopsies for histomorphometry). The beneficial effect of aromatase inhibitors (AIs) and inactivators on breast cancer depends on reducing levels of circulating estrogens in the peripheral blood. There appears to be variability in the effects of AIs on bone in experimental animals, and this variability may not be the same in humans. In general, bone loss is an expected side effect of the AIs. For postmenopausal women receiving adjuvant anastrozole or other AIs, a BMD measurement using dual-energy x-ray absorptiometry is recommended, to be repeated every 1-2 years. Regular physical exercise is advised together with added calcium 1500 mg and vitamin D 800 U daily. If the T-score reaches a level of > −2.5, or if it is between −1.5 and -2.5 in the presence of a fragility fracture or vertebral compression fracture, or if height loss > 2 cm occurs or BMD decreases > 3% in 1 year at the lumbar spine or > 5% at the femoral neck, bisphosphonate therapy should be considered.