There are increasing numbers of long-term survivors from breast cancer who will have received combination endocrine treatments alone or in addition to cytotoxic chemotherapy. As a result, many of these individuals are at increased risk of osteoporosis, largely because of the endocrine changes induced by treatment characterised by a reduction in the level of bioavailable oestradiol. The associated increase in bone turnover that accompanies cancer treatment induced bone loss (CTIBL) can lead to a 4050% increase in the rate of fragility fractures.
The use of bisphosphonates in early cancer has become increasingly important to prevent adverse effects of cancer treatments on bone health. These include chemotherapy induced ovarian failure and the use of aromatase inhibitors. Bisphosphonate strategies, similar to those used to treat post-menopausal osteoporosis, are the intervention of choice for patients with low bone mineral density (BMD) or rapid bone loss, along with adequate calcium and vitamin D intake and a healthy lifestyle. The results of several intervention studies with zoledronic acid in early breast cancer indicate that BMD is maintained and increased bone turnover normalised. There are also preliminary data from smaller studies using oral bisphosphonates at standard osteoporosis doses, as well as the new bone targeted agent denosumab, an antibody to RANKL. In addition to the beneficial effects of bisphosphonates on bone health, some data from trials in early breast cancer suggest that they may also reduce cancer recurrence rates in the adjuvant setting.
Guidelines on the management of CTIBL have recently been formulated and utilise a risk adapted strategy similar to that used in the management of postmenopausal osteoporosis, with the exception that the recommended BMD threshold for intervention with pharmacological treatments is somewhat higher due to the accelerated rate of bone loss.