BIOCHEMICAL PARAMETERS OF BONE METABOLISM IN BONE METASTASES OF SOLIDTUMORS (REVIEW)

The role of biochemical markers of bone metabolism in the diagnosis an d monitoring of bone metastases in solid tumors is reviewed. Emphasis is on the recently developed markers, which may provide a more accurat e quantitation of bone metabolism. In metastatic bone disease, bone fo rmation and resorption become uncoupled processes, leading to predomin antly osteoblastic or osteolytic metastases. In osteolytic metastases, bone resorption is enhanced without appropriate acceleration of bone formation. In osteolytic metastases the resorption markers are indicat ed for the detection of bone metastases. Urinary pyridinium crosslinks and serum collagen telopeptides are sensitive and specific markers of bone resorption. These markers, can often identify bone metastases be fore visualization by imaging techniques. When osteolytic lesions are responding to treatment the physiologic coupling between bone resorpti on and formation is partly restored. An increase in formation markers, bone specific isoenzyme of alkaline phosphatase (BSAP), osteocalcin ( OC) and carboxyterminal propeptide of collagen type I (PICP), will the n closely reflect restoration of coupling. In osteoblastic metastases, bone formation markers can accurately indicate early and advanced bon e involvement. Bone resorption markers are less sensitive in these ost eoblastic lesions. The collagen telopeptides however, are resorption m arkers with the ability to detect early bone metastases. Osteoblastic lesions responding to therapy are indicated by declining values of for mation as well as resorption markers. The precise role of the recently developed markers of bone metabolism in early diagnosis and monitorin g of bone metastases needs further evaluation in longitudinal studies. Since the delicate derangements in bone metabolism may be obscured in mixed patient groups, these studies should address uniform patient gr oups with respect to the primary tumor type.