FREE-TO-TOTAL PROSTATE-SPECIFIC ANTIGEN RATIO AS A SINGLE TEST FOR DETECTION OF SIGNIFICANT STAGE T1C PROSTATE-CANCER

Purpose: We investigated whether impalpable, invisible (stage T1c) but significant prostate cancer can be detected better by determining the free-to-total prostate specific antigen (PSA) ratio of equivocal PSA serum levels. Materials and Methods: The specificity of free-to-total PSA ratio using research monoclonal enzyme immunoassays was compared t o that of PSA greater than 4.0 ng./ml. in 117 consecutive patients wit h PSA 3 to 15 ng./ml. (Hybritech Tandem-R assay) due to untreated beni gn prostatic hypertrophy or prostate cancer. Of the patients 77% under went adenectomy or radical prostatectomy with thorough pathological ev aluation of surgical specimens. Results: Benign prostatic hypertrophy had a greater median free-to-total PSA ratio than stages T1c and T2 or greater prostate cancer (0.16 versus 0.09 and 0.11 ng./ml., p = 0.000 1 and p = 0.0268, respectively). In stage T1c prostate cancer, areas u nder receiver operating characteristic curves were 0.58 and 0.84 for P SA and free-to-total PSA ratio, and free-to-total PSA ratio correlated with prostate volume (r = 0.49, p = 0.005) and Gleason score (r = -0. 37, p = 0.036). Pathologically, 84% of stage T1c cancers were signific ant and comparable to stage T2 or greater cancers. Conclusions: Free-t o-total PSA ratio enhances the efficacy of PSA measurement by improvin g specificity for detecting impalpable, invisible but significant stag e T1c prostate cancer.