CAN COMPLEXED PROSTATE SPECIFIC ANTIGEN AND PROSTATIC VOLUME ENHANCE PROSTATE CANCER DETECTION IN MEN WITH TOTAL PROSTATE SPECIFIC ANTIGEN BETWEEN 2.5 AND 4.0 NG./ML.

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Abstract
We assessed whether complexed prostate specific antigen (PSA) and complexed PSA referenced variables would enhance prostate cancer detection in men with serum total PSA between 2.5 and 4.0 ng./ml. Transition zone and total prostate gland volumes were determined in 151 men who underwent prostate biopsy using an 11 core biopsy strategy. In addition to measuring the Bayer section sign complexed PSA assay, we also calculated 2 computed complexed PSA values (Hybritech parallel total PSA--Hybritech free PSA and Bayer total PSA--Hybritech free PSA). We calculated 8 volume referenced variables using total and complexed PSA, and 2 computed complexed PSA values by dividing each value by the total prostate and transition zone volumes. Of the 151 patients 37 (24.5%) had cancer. In 10 of the 37 men with cancer (27%) a positive core was present in only 1 or more of the 5 alternate regions not sampled by conventional sextant biopsies. At 92% sensitivity a cutoff value of 2.3 ng./ml. for complexed and 31% for free-to-total PSA provided 42% and 11% specificity, respectively (p <0.001). In the 116 men with a total prostate volume of 30 cc or greater at 92% sensitivity the specificity of complexed PSA density (55%) and complexed PSA adjusted for transition zone volume (52%) were better than that of complexed (40%) and free-to-total (11%) PSA. In the 35 men with a total prostate volume of less than 30 cc at 92% sensitivity the specificity of complexed PSA (50%), complexed PSA density (55%) and complexed PSA adjusted for transition zone volume (55%) were significantly better than that of free-to-total PSA (8%, p <0.001). The area under the curve of complexed PSA was almost identical to that of the 2 computed complexed PSA calculations. A substantial proportion of men with total PSA values between 2.5 and 4.0 ng./ml. had prostate cancer. Complexed and computed complexed PSA were more specific than the free-to-total PSA ratio when total PSA was between 2.5 and 4.0 ng./ml. A 2.3 ng./ml. threshold for complexed and computed complexed PSA appears to stratify prostate biopsy results in men with total PSA between 2.5 and 4.0 ng./ml. The computed complexed PSA calculation appears to be equivalent to the complexed PSA serum assay for detecting cancer. Volume referenced complexed PSA performed better than complexed PSA in men with a total prostate volume of 30 cc or greater compared to men with a total prostate volume of less than 30 cc.