Prospective Trial for clinical evaluation of TRACP 5b as serum marker of bone resorption and for monitoring an oral clodronat-medication in osteolytic metastases of breast carcinoma

Abstract

862 Background:Tartrate-resistent acid phosphatase (TRACP 5b) has been described as marker enzyme of bone resorbing osteoclasts and can be recorded quantitatively. Throughout regular measurement during treatment with bisphosphonates the efficacy of this therapy can be controlled. The aim of this study was to test the clinical relevance of TRACP 5b-measurements within the scope of monitoring patients with osteolytic bone metastases of breast cancer Methods:18 patients with BC and osteolytic bone metastases have been included. All patients received an oral clodronate medication (1600 mg/d). TRACP 5b was measured as baseline value and every two weeks. TRACP 5b (standard value for postmenopausal women: 2,8 ± 0,7 U/l) was measured with an enzyme-immuno assay of medac Diagnostika (Wedel, Germany). Results:The baseline values of all patients showed a significant elevation of TRACP 5b (7,34 vs 2,8 U/l). There was a clear difference in the baseline values between patients (group 1) with > 3 regions of bone metastases and patients (group 2) with < 3 regions of bone metastases (10,34 vs 5,72 U/l). In the course of controls during therapy with clodronate both groups showed an continuous decrease of TRACP 5b levels. After more than 2 months of therapy in both groups there was a significant decrease of TRACP 5b levels compared with the TRACP 5b levels in the first two months (group 1: 3,91 vs 4,68 U/l; group 2: 12,39 vs 8,23 U/l). In patients with estimated progressive disease in radiologic controls we found no significant but a distinct re-increase of TRACP 5b levels whereas in patients with stable disease TRACP 5b levels decreased further on. Conclusions:The results demonstrate that TRACP 5b is a valid marker of bone resorption in osteolytic metastases of breast carcinoma. TRACP 5b levels correlate with the extent of bone metastases. To achieve a clear reduction of TRACP 5b levels a antiresorptive therapy over several weeks is necessary. Furthermore determination of TRACP 5b may indicate a progression or stable disease of bone metastases during therapy. No significant financial relationships to disclose.