Prostate cancer screening within a prostate specific antigen range of 3 to3.9 ng./ml.: A comparison of digital rectal examination and free prostate specific antigen as supplemental screening tests

Purpose: Performing biopsy in all men with a serum prostate specific antige n (PSA) of 3 to 3.9 ng./ml. increases the sensitivity of prostate cancer sc reening compared with a PSA cutoff of 4 ng./ml. but decreases specificity a nd may contribute to over diagnosis. Therefore, we evaluated the detection rate and specificity attributable to digital rectal examination and percent free PSA within the PSA range of 3 to 3.9 ng./ml. Materials and Methods: Serum PSA was determined in 20,716 participants in t he Finnish population based screening trial. Supplementary digital rectal e xamination was offered to men with a PSA of 3 to 3.9 ng./ml. during 1996 to 1998 (protocol 1). Those with a suspicious digital rectal examination find ing were referred for biopsy. The screening algorithm was modified by subst ituting percent free PSA for digital rectal examination with a cutoff of 16 % as a biopsy criterion in 1999 (protocol 2). In addition, biopsies were pe rformed in all men with PSA 4 ng./ml. or greater. Results: A total of 23 cancers (2.9%) were detected by digital rectal exami nation among 801 men, while percent-free PSA resulted in the diagnosis of 1 3 cases (4.8%) among 270 men with a PSA of 3 to 3.9 ng./ml. The detection r ate of tumors with a Gleason score of 5 or greater increased from 1.6% (13 of 801 cases) to 4.4% (12 of 270) in the modified screening program. The PS A cutoff of 3 ng./ml. alone showed 88.6% and 87.5% specificity in protocols 1 and 2 but specificity increased to 93.3% and 91.7% using digital rectal examination and percent free PSA, respectively. Conclusions: Using percent free PSA increased the detection rate of aggress ive disease compared with digital rectal examination and provided higher sp ecificity than PSA alone.