Impact of denosumab on bone mass in cancer patients

Cancer therapy-induced bone loss (CTIBL) is a form of secondary osteoporosis associated with systemic chemotherapy and hormonal ablation therapy. The monitoring and treatment of CTIBL is an important component of comprehensive cancer care, especially for patients with curable disease and long life expectancies. Whereas oral bisphosphonates remain the most commonly used therapeutic option for CTIBL, additional treatment options may be required for patients who do not respond adequately or are intolerant to bisphosphonates, have renal insufficiency, or are receiving treatment with nephrotoxic medications. For these patients, denosumab, a monoclonal antibody targeting the receptor activator of nuclear factor-κB ligand (RANKL), offers an effective and well-tolerated alternative. Several recent randomized trials have examined the use of denosumab as treatment for CTIBL associated with hormone ablation therapy for breast and prostate cancer. Recent data suggest a possible role for RANKL inhibitors in both chemoprevention and the prevention of cancer recurrence through direct effects on breast tissue and breast cancer stem cells. The outcomes of several international Phase III clinical trials currently underway will help clarify the role of denosumab in patients undergoing cancer therapy.

Current and emerging treatment strategies for breast cancer-induced bone loss

Breast cancer increases a woman's risk for bone loss. Bone loss occurs due to the skeletal fragility associated with malignancy, the occurrence of premature ovarian failure secondary to chemotherapy, and the loss of bone mineral density (BMD) associated with antiestrogen therapies. Tamoxifen has been shown to reduce BMD among premenopausal women, and aromatase inhibitors, which have become a standard therapy among postmenopausal women, increase bone loss and the risk of fracture. Bisphosphonates preserve BMD among women with breast cancer, both among postmenopausal women and those with a history of significant bone loss. The effect among premenopausal women appears modest. Despite the protective effect on bone density, a reduction in the risk of fracture has not yet been established. Therefore, other risk factors for fracture must be addressed, such as dietary intake, vitamin D, and assessment of other potentially modifiable conditions. Newer agents that target the receptor activator of nuclear factor-κB (RANK) system and RANK ligand (RANKL), such as denosumab, represent an emerging class of medications that may also preserve BMD in this population.