Metastatic workup of patients with prostate cancer employing alkaline phosphatase and skeletal alkaline phosphatase

Purpose: To compare the efficacy of two tests, alkaline phosphatase (AP) and skeletal alkaline phosphatase (SAP) as staging markers to discriminate patients with cancer of the prostate (CaP) with bone metastases (M+) from those without bone metastases (Mo). Materials and Methods: Patients with previously untreated CaP were entered in the retrospective analysis. Serum concentrations of AP (n = 215) and SAP (n = 73) were available. After staging the patients could be divided into 2 groups: Group I: patients with CaP and bone metastases (cT2-4 NxMoss; AP: n = 40; SAP: n = 21) Group II: patients with CaP without bone metastases (cT3-4 Nx Mo; pT1-3 No Mo; AP: n = 175; SRP: n = 52) Results: None of the Mo patients but 71% of the M+ patients exhibited a SAP value above the reference range (< 19 ng/ml). This difference is statistically significant (p < 0.001) and resulted in a sensitivity and specificity of 71% and 100% respectively. The Youden-index is 0.7. In contrast 7% of the Mo patients and only 13% of the M+ patients exhibited a AP value above the reference range (< 170 U/l). This difference is statistically not significant (p = 0.71) and resulted in a sensitivity and specificity of 13% and 93%, respectively. The Youden-index is 0.06. Conclusion: SAP could become a useful marker in the evaluation of patients with newly diagnosed CaP as it provides more information than AP concerning the skeletal status of these patients.