Relationship between prostate-specific antigen, clinical stage, and degree of bone metastasis in patients with prostate cancer: comparison with prostatic acid phosphatase and alkaline phosphatase.

BACKGROUND

The study was designed to examine the relation of the levels of prostate-specific antigen (PSA), prostatic acid phosphatase (PAP), and alkaline phosphatase (ALP) to clinical stage and bone metastasis in prostate cancer patients.

METHODS

Serum PSA, PAP, and ALP levels were evaluated in 272 patients with prostate cancer. The relation of the level of PSA, PAP, and ALP to clinical stage and to degree of bone metastasis were examined by a multiple comparison method using ranks. The superiority of a marker in the rate of detection of bone metastasis was evaluated with receiver operating characteristic (ROC) curves. The correlation coefficients of the order of the extent of bone metastasis with PSA, PAP, and ALP were examined with Spearman's rank order correlation coefficient test.

RESULTS

The levels of PSA showed significant differences among 8 pairs of clinical stages. In contrast, the levels of PAP showed significant differences among 6 pairs, and the levels of ALP showed significant differences among only 4 pairs. The area under the ROC curves of PSA, PAP, and ALP for revealing bone metastasis was 84.9%, 81.4%, and 77.3%, respectively. The correlation coefficients of the order of extent of disease (EOD) with log (PSA), log (PAP), and log (ALP) were 0.346, 0.394, and 0.618, respectively, and the levels of ALP showed the most significant differences regarding the extent of bone metastasis.

CONCLUSION

PSA was the best marker for differentiating clinical stages, but showed limited reliability for stratifying the extent of bone metastasis.