Mechanisms in the skeletal complications of breast cancer.

Breast cancer is the most common malignancy in women, with a worldwide prevalence of 1.5 million throughout the industrialized countries. Its mortality rate is second only to lung cancer in the USA and Europe. Its high incidence and prevalence makes it a major public health problem. Up to one-third of women with early stage breast cancer will eventually succumb to the disease, and most of these will develop bone metastases during the course of the disease. Approximately 70% of patients with breast cancer have bone metastases, with 27% having lung and liver metastases. Hypercalcemia also is very common in advanced breast cancer, manifesting itself in one-third of patients late in the disease. Breast cancer accounts for approximately 25% of the cases of hypercalcemia in cancer. The major skeletal complications of breast cancer--hypercalcemia and bone metastases--almost certainly share certain mechanisms and these will be discussed.