Serum bone alkaline phosphatase in the follow-up of skeletal metastases

The efficacy of bone alkaline phosphatase (ALP) isoenzyme measurement, using a lectin precipitation method, in confirming metastatic sites was assessed in 65 patients with cancer and skeletal (n = 44), hepatic (n = 15) or lymph node (n = 6) metastases; the control group consisted of 33 healthy adults. In all subjects, total ALP activity and osteocalcin were also assayed. Our results confirm that isoenzyme analysis is more specific than total enzymatic activity measurement in the identification of bone metastases: the mean for total ALP values was increased in all patients, while significantly high mean values of bone fraction (p<0.05 by ANOVA) were observed only in patients with bone secondaries. In the serial monitoring of 9 patients with skeletal metastases, bone ALP values correlate with pain symptomatology: a progressive decrease in bone isoenzyme activity was observed in patients with a complete remission of pain after radiotherapy, while a progressive increase in activity was observed in the presence of increased bone pain. The measurement of bone isoenzyme activity is useful in screening for skeletal metastases; levels appear to correlate with the course of bone symptomatology, thus providing useful objective evidence of response to treatment.