Cancer Treatment-Induced Bone Loss in women with breast cancer

Osteoporosis is one of the most frequent diseases in postmenopausal women, leading to an increased fracture risk due to the physiologic loss of the bone protective effects of estrogen. Hereby, several risk factors for fracture such as prevalent fracture, low bone mineral density (BMD), age, low body mass index, family history, tendency to falls, smoking, use of SSRIs, glucocorticoid use etc. have been identified. In addition, the further reduction in endogenous estrogens with chemotherapy (CHT), GnRH analoga or aromatase inhibitors (AIs) continuously increases fracture risk. Breast cancer (BC) on the other hand is the most frequent cancer type in women. Recent reports indicate a continuous increased incidence, whereas mortality, due to early diagnosis and treatment improvements, is decreasing. Dependent on specific tumor characteristics, radiation, CHT, antibody treatment as well as endocrine treatment have been included into the adjuvant clinical treatment setting. Some but not all of these cancer-specific treatments interfere with bone turnover, leading to an accelerated bone loss referred to as cancer treatment-induced bone loss (CTIBL). Whereas CHT leads to an unspecific increase in bone resorption, AI reduces residual serum endogenous estrogen level and is associated with a decrease in BMD and increased fracture risk. Independent of the type of AI administered, bone loss is 2-3-fold increased compared with healthy, age-matched postmenopausal controls. Therefore, several guidelines have emerged to help managing CTIBL in women with BC including strategies to identify and treat those at highest risk for fractures. This review summarizes the current knowledge on CTIBL and fracturing risk and indicates preventative strategies.