Biochemical Markers of Bone Metabolism in Metastatic Bone Disease

Skeletal metastases characteristically develop in the course of many malignant conditions but mainly, in descending order of frequency, in plasmocy- toma and mammary, prostatic, bronchial, renal cell, and thyroid cancer. Their manifestation is usually accompanied by prognostically unfavorable and sometimes life-threatening complications (pain, pathological fractures, nerve compression, hematopoietic disorders, malignant hypercalcemia). Early diagnosis and continuous follow-up of bone metastases is thus of major clinical and especially therapeutic relevance, practical measures usually consisting of a combination of radiographic, nuclear medical, biopsy/ histological, and clinical laboratory methods. All these techniques have typical methodological limitations in terms of specificity and sensitivity. Metastatic focal lesions of cancellous bone, for example, are not reliably detectable radiographically until the advanced stage, i.e., from a size of just under lcm. Skeletal scintigraphy, although suitable for the early detection especially of osteoblastic processes, often does not allow accurate assessment of tumor status in the absence of prior findings. Conventional bone biopsy appears unsuitable as an early diagnostic tool in view of its low success rate, and as an invasive procedure it is of utility only after relevant changes have been confirmed radiographically. Immunohistochemical techniques, however, have led to a marked improvement in the predictive value of biopsy methods in this field (Diel et al. 1992; see also Diel et al., this volume).