Background: The serum marker tartrate-resistant acid phosphatase isoform 5b (TRACP 5b) is considered a specific parameter of osteoclast activity and a useful marker of bone resorption. Regarding the utility of TRACP 5b in bone metastases, this review aims to draw clinically relevant conclusions.
Materials and methods: The available literature data regarding the laboratory methods, the characteristics of TRACP 5b and the clinical data, as well as our own results about TRACP 5b in cancer patients has been reviewed.
Results: In contrast to enzymatic assays, two new assays based on a monoclonal antibody and on heparin-induced inhibition of TRACP 5a, respectively, demonstrated low biological and analytical variabilities in healthy subjects as well as in patients with osteoporosis. Up to now, only a few studies have evaluated the utility of TRACP 5b in cancer patients with bone metastases. In these studies, the sensitivity of TRACP 5b was higher compared to other markers. Furthermore, TRACP 5b activity correlates with the response to the treatment of bone metastases.
Conclusion: Although the clinical data available are promising, the results are still preliminary. In addition to further evaluation of the analytical method, more studies in cancer patients are needed to establish TRACP 5b in the diagnostic procedure and in the therapy monitoring of bone metastases.