Serum tartrate resistant acid phosphatase as a potential marker of bone metastasis from breast cancer

Background: Tartrate resistant acid phosphatase (TRACP) is exclusively localized in osteoclasts and has been suggested to be a unique marker of bone metastasis. Patients and Methods: TRACP activity using an improved spectrophotometric assay was measured in 56 healthy volunteers and 113 breast cancer patients, including 35 with bone metastases (BM). Results: TRACP activities (IU/l, mean±SD) of normal subjects in pre- and post-menopausal women were 5.7 ± 1.3 and 6.6 ± 1.2, respectively (p<0.02). The specificity, sensitivity, and accuracy of TRACP in patients, were 91.0%, 65.7%, and 83.2%, respectively. TRACP was significantly higher in patients with BM than in patients without BM (p <0.01). In patients with BM, TRACP increased in proportion to the number of BM. Regarding clinical assessment of treatment of BM, TRACP was significantly higher in patients with progressive disease. Conclusion: TRACP is a useful marker of metastatic bone disease and response to treatment in breast cancer patients.