A Critical Analysis of Calcium Kinetics in Metastatic Cancer

Abstract

SummaryStudies on the kinetics of calcium metabolism were carried out in 12 women with advanced breast cancer and in 7 patients with miscellaneous metastatic bone cancers. Each subject was injected i.v. with either 45Ca or 47Ca and followed by determining the time-course of the plasma specific activity, the activity excreted in urine and faeces, as well as the stable calcium excreted in urine. The kinetic analysis was based on a mammillary three-compartment model. In five premenopausal oophorectomized women the accretion rate and the daily urinary excretion of calcium were increased. The trend of the dianges indicated both loss of oestrogenic and increase in pituitary activity. Of 7 postmenopausal women, calcium kinetics was normal in five and abnormal in two patients. There was hypophosphataemia, low calciuria and high albeit normal accretion rate in one whereas in the other patient a high plasma phosphate concentration, moderate hypercalciuria and a markedly lowered accretion rate was observed. The remaining 7 patients had rather normal kinetics: the accretion rate was always normal and the daily urinary calcium was sometimes abnormal. The changes of calcium metabolism occurred whether the cancer process was arrested, improved or progressed. The data of this study evidence against the idea that disturbances in the kinetics of calcium are simply a matter of the extent and the activity of bone métastasés and show that they are influenced by the endocrine milieu.