Evidence of Benefit
The median time from the second blood draw to cancer diagnosis was 16 years. Median follow-up for men not diagnosed with prostate cancer was 21 years. PSA assays were done in plasma stored under conditions that preserved the integrity of PSA. TPSA and tPSAv were highly correlated. Both tPSA and tPSAv were associated with prostate cancer in univariate models (P < .001). Men subsequently diagnosed with prostate cancer have increased tPSA and increased tPSAv up to 20 years before diagnosis. Overall predictive accuracy of tPSA plus tPSAv was equivalent to tPSA alone (concordance index: 0.771 tPSA alone; 0.712 tPSAv alone; 0.771 tPSAv added to tPSA). TPSAv did not aid long-term prediction of cancer in early middle-aged men.
Alteration of PSA cutoff level
A number of authors have explored the possibility of using PSA levels lower than 4.0 ng/mL as the upper limit of normal for screening examinations. One study screened 14,209 white and 1,004 African American men for prostate cancer using an upper limit of normal of 2.5 ng/mL for PSA. A major confounding factor of this study was that only 40% of those men in whom a prostate biopsy was recommended actually underwent biopsy. Nevertheless, 27% of all men undergoing biopsy were found to have prostate cancer. Several collaborating European jurisdictions are conducting prostate cancer screening trials, Rotterdam (the Netherlands) and Finland among them. In Rotterdam, data for 7,943 screened men between the ages of 55 and 74 years have been reported. Of the 534 men who had PSA levels between 3.0 ng/mL and 3.9 ng/mL, 446 (83.5%) had biopsies and 96 (18%) of these had prostate cancer. In all, 4.7% of the screened population had prostate cancer. In Finland, 15,685 men were screened and 14% of screened men had PSA levels of at least 3.0 ng/mL. All men with PSAs higher than 4.0 ng/mL were recommended to diagnostic follow-up by DRE, ultrasound, and biopsy; 92% complied, and 2.6% of the 15,685 men screened were diagnosed with prostate cancer. Of the 801 men with screening PSAs between 3.0 ng/mL and 3.9 ng/mL (all biopsied), 22 (3%) had cancer. Of the 1,116 men with screening PSAs between 4.0 ng/mL and 9.9 ng/mL, 247 (22%) had cancer; of the 226 men with screening PSAs of at least 10 ng/mL, 139 (62%) had cancer. Several factors could have contributed to these differences, including background prostate cancer prevalence, background screening levels, and details regarding diagnostic follow-up practices; the necessary comparative data are not available.
Another study adopted a change in the PSA cutoff to a level of 3.0 ng/mL to study the impact of this change in 243 men with PSA levels between 3.0 ng/mL and 4.0 ng/mL. Thirty-two of the men (13.2%) were ultimately found to have prostate cancer. An analysis of radical prostatectomy specimens from this series found a mean tumor volume of 1.8 cc (range, 0.6-4.4). The extent of disease was significant in a number of cases, with positive margins in five cases and pathologic pT3 disease in six cases.