Calcium metabolism in breast cancer

Patients with breast cancer and bone destruction were found to have a pattern of calcium metabolism which was broadly similar to that found in other malignancies, but different from that in primary hyperparathyroidism. Thus, they tended to have reduced absorption of calcium from the intestine, elevated endogenous faecal calcium and normal or reduced urinary cyclic AMP excretion. Since prostaglandin synthetase inhibitors have been shown to inhibit breast cancer-induced osteolysis in vitro we have attempted to reduce bone destruction and serum calcium in patients with hypercalcaemia complicating breast cancer using these agents. High doses failed to reduce the serum calcium or the urinary hydroxyproline: creatinine ratio in ten patients with skeletal metastases, four of whom had hypercalcaemia.