Abstract
The rate of calcification of new bone (accretion rate) was measured by a radioisotope technique in 20 patients with carcinoma of the breast, 14 patients with multiple myelomatosis, five patients with Paget's disease of bone, and in six patients with solitary, non-osseous tumours. The rate of bone destruction was assessed in these patients by the measurement of the rate of urinary calcium excretion. In the patients with carcinoma of the breast and bone metastases there was a marked increase both in the accretion rate and in the urinary calcium excretion suggesting an osteoblastic response to bone destruction. An osteoblastic response was also present in the patients with multiple myelomatosis but was not correlated with the urinary calcium excretion. In patients with Paget's disease of bone, high values of accretion rate were found indicating very active new bone formation.