IS THE SKELETAL ALKALINE-PHOSPHATASE A VALUABLE STAGING MARKER FOR BONE METASTASES IN PATIENTS WITH PROSTATE-CANCER

Purpose: For patients with prostate cancer (CaP) the proof of osteobla stic bone metastases is decisive regarding the prognosis as well as th e therapeutical concept. To evaluate the efficiency of skeletal alkali ne phosphatase (SAP) as staging marker for bone metastases in prostate cancer, SAP was measured in CaP-patients with and without bone metast ases compared with prostate-specific antigen (PSA) as the marker of ch oice till now. Method: 73 patients with histological proven, but still untreated CaP were entered into the study. After staging the patients were devided into 3 groups: group I: patients with CaP and bone metas tases (n = 21), group II: patients with locally advanced CaP without b one metastases (n = 26), group III: patients with clinically localized CaP without bone metastases (n = 26). Serum concentration for SAP and PSA were determined using radioimmunassay. As reference range we defi ned serum concentrations for SAP < 19 ng/ml and for PSA < 100 ng/ml. R esults: 71% of the patients with bone metastases (group I) showed elev ated SAP and PSA serum concentrations. In contrast, patients without b one metastases (group II + III) have normal SAP-values (< 19 ng/ml) an d in 19% of the cases elevated PSA-values (> 100 ng/ml). This resulted in a sensitivity and specifity of 71% and 100% for SAP and 71% and 81 % for PSA. The positive predictive value for osteoblastic bone metasta ses was 100% for SAP and 60% for PSA. Conclusion: SAP is a useful stag ing marker in prostate cancer and can contribute for an early detectio n of osteoblastic bone metastases.