The use of serum isoenzymes of alkaline and acid phosphatase as possible quantitative markers of tumor load in prostate cancer.

The tumor burden of 98 patients with metastatic prostatic cancer was compared longitudinally with the activities of bone (BAP) and liver isoenzymes (LAP) of alkaline phosphatase, total acid phosphatase (AcP), and prostate-specific acid phosphatase (PAP). A quantitative association between these enzyme markers and the tumor mass was suggested by comparing the enzymes with 1) both the treatment response and the estimation of metastasis by radionuclide bone scanning; 2) metastasis based upon radiographic evidence. In addition, an apparent extensive pretreatment bone tumor load was predictive for an elevated BAP activity, which was also a suggestive poor prognosis as previously reported. An elevation of PAP, in contrast to AcP, may precede the clinical disease progression in some patients. Data presented in this report have indicated that the levels of these enzymes compared well with the extent of tumor involvement and therefore may be considered suitable as adjuvant and even quantitative biochemical markers of bone and liver metastasis.