The role of prostate specific antigen as a tumor marker in men with advanced adenocarcinoma of the prostate.

Serial serum prostate specific antigen levels were obtained every 4 hours during a 24-hour interval from 8 men with stage D adenocarcinoma of the prostate. No therapeutic or diagnostic manipulations occurred during sample procurement, so that the amount of fluctuation of serum prostate specific antigen levels that can be expected in these patients could be determined. The coefficient of variation for each man ranged from 1.16 to 10.94 per cent, which was not statistically higher than the expected 4.39 and 11.44 per cent coefficient of variation determined with a control sample. The maximum percentage variations above and below the mean were 19.3 and 17.7 per cent, respectively. The average percentage variation in all patients was within 7.6 per cent greater than and 7.6 per cent less than the mean value of prostate specific antigen. Thus, prostate specific antigen appears to be a reliable tumor marker because there is minimal random fluctuation when serial levels are obtained in men with advanced prostate cancer. Based on these findings certain guidelines are suggested.