Characterization of secretion pattern of human prostatic acid phosphatase: a reassessment

The daily variation of serum levels of prostatic acid phosphatase (PAP) determined by the Roy enzymatic method was investigated in 10 patients with metastatic prostatic cancer and in 10 patients without prostatic disease. Duplicate serum samples were obtained from all patients on the same day at 8 AM, 12 PM, 4 PM, and 8 PM. Statistical analysis of the mean PAP levels at the four sampling times in both groups of patients demonstrated no evidence of circadian or diurnal rhythmic variation. Prostate cancer patients did show significantly greater variability in daily PAP than patients without prostatic disease, although a distinct pattern of secretion was not observed in either group. These results underscore the potential inaccuracy of the use of single determination of serum PAP as a parameter of response in patients with metastatic prostatic cancer and in the staging of patients with clinically localized prostatic malignancy. Evaluation of trends of PAP levels over time, however, continues to play a major role in the assessment and management of patients with prostatic carcinoma.