[Is skeletal alkaline phosphatase a valid staging marker in detection of osteoblastic skeletal metastases of prostate carcinoma?].

PURPOSE

For patients with prostate cancer (CaP) the proof of osteoblastic bone metastases is decisive regarding the prognosis as well as the therapeutical concept. To evaluate the efficiency of skeletal alkaline phosphatase (SAP) as staging marker for bone metastases in prostate cancer, SAP was measured in CaP-patients with and without bone metastases compared with prostate-specific antigen (PSA) as the marker of choice till now.

METHOD

73 patients with histological proven, but still untreated CaP were entered into the study. After staging the patients were divided into 3 groups: group I: patients with CaP and bone metastases (n = 21), group II: patients with locally advanced CaP without bone 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 defined serum concentrations for SAP < 19 ng/ml and for PSA < 100 ng/ml.

RESULTS

71% of the patients with bone metastases (group I) showed elevated SAP and PSA serum concentrations. In contrast, patients without bone metastases (group II + III) have normal SAP-values (<19 ng/) and in 19% of the cases elevated PSA-values (>100 ng/ml). This resulted in a sensitivity and specificity of 71% and 100% for SAP and 71% and 81% for PSA. The positive predictive value for osteoblastic bone metastases was 100% for SAP and 60% for PSA.

CONCLUSION

SAP is a useful staging marker in prostate cancer and can contribute for an early detection of osteoblastic bone metastases.