Calcium excretion (CaE) in metastatic breast cancer.

In 51 women with metastatic breast cancer calcium excretion per litre of glomerular filtrate (CaE) values were persistently higher in those with bone secondaries than in those with only soft tissue involvement despite a normal range of serum calcium in both groups. Measurement of CaE in 8 further patients who were severely hypercalcaemic as a result of their advanced breast cancer revealed the degree to which calcium resorption from bone secondaries and renal dysfunction contributed to the hypercalcaemia. Thus, in patients with breast cancer, CaE provides a reliable indicator of early changes of calcium homeostasis. It may provide an objective indication of progression of bone secondaries and also has important therapeutic implications in established hypercalcaemia.