The mean age (±SD) of the 123 subjects in this study was 62.2±8.2 years (41-83 years) with a racial distribution as follows: Caucasian: 90.2%; African American: 6.5%; and Other: 3.2%. In the 120 men in whom information was available, 79% of the non-cancer group had a DRE non-suspicious for cancer, while in the cancer group 71% of men had a DRE non-suspicious for cancer. Within the cancer group, 52% of men had a biopsy Gleason score of 6, 38% had a score of 7, and 10% had a score of 8 or 9.
The utility of the isoforms of free PSA, particularly [-2]proPSA was examined in the entire dataset (PSA range 0.48-33.18 ng/mL) and in the clinically important ranges incorporating 4-10 ng/mL total PSA and 2-10 ng/mL total PSA. Overall, the cancer and non-cancer groups were equivalent with respect to age (non-cancer: 61.7±8.6 years, cancer: 62.6±7.8 years) as well as total PSA concentrations (non-cancer: 6.80±5.20 ng/mL, cancer: 6.94±5.1 ng/mL). A comparison between the two groups for the measured PSA derivatives and calculated values as well as testosterone is shown in . %fPSA was significantly lower (p<0.05) in the cancer group while [-2]proPSA and %[-2]proPSA were significantly higher in the cancer group.
Comparison of mean serum values for the non-cancer and cancer groups for all subjects (n=123)
Results for the 4-10 ng/mL and 2-10 ng/mL PSA truncated ranges were similar and therefore only the 2-10 ng/mL data are presented here. In that range, similar to the overall range of data (), %[-2]proPSA was significantly higher (p<0.05) in the cancer group, as was [-2]proPSA alone and the ratio of [-2]proPSA/BPSA. %fPSA was equivalent between the cancer and non-cancer groups.
Comparison of mean serum values for the non-cancer and cancer groups for subjects in the 2-10 ng/mL PSA range (n=89)
ROC analysis of the non-cancer controls and cancer cases in all subjects is shown in and . Of the PSA derivatives, %[-2]proPSA had the greatest area under the curve (AUC) of 0.69 followed by %fPSA with an AUC of 0.61. At a sensitivity of 90 percent, corresponding specificity was 32% for %fPSA and 37% for %[-2]proPSA while at 95% sensitivity, specificity was 30% for %fPSA and 15% for %[-2]proPSA, respectively. At the optimal cutoff point for %[-2]proPSA (1.4%) corresponding to the maximal sum of sensitivity and specificity, sensitivity was 60% with a specificity of 70%. A logistic regression model was constructed combining PSA, BPSA, %fPSA, %[-2]proPSA, [-2]proPSA/BPSA, and testosterone, although only %[-2]proPSA was significant in the final model. The AUC was 0.73 and sensitivity at 90% and 95% specificity was 39% and 28%, respectively ().
ROC analysis for all subjects (n=123)
ROC analysis for all subjects (n=123) comparing PSA (AUC=0.52), %fPSA (AUC=0.61), %[-2]proPSA (AUC=0.69), and a composite logistic regression model combining PSA, BPSA, %fPSA, %[-2]proPSA, %[-2]proPSA/BPSA, and testosterone (AUC=0.73)
In the 2-10 ng/mL PSA range, individually, %[-2]proPSA again had the largest AUC (0.73) while the AUC for %fPSA was 0.53 (, ). When PSA, BPSA, %fPSA, %[-2]proPSA, [-2]proPSA/BPSA, and testosterone were evaluated together using logistic regression (), only %[-2]proPSA was a significant discriminator for prostate cancer (AUC=0.73). The specificities for %fPSA, %[-2]proPSA, and the logistic regression model at 90% sensitivity were 18%, 41%, and 32%, respectively and at 95% sensitivity were 15%, 31%, and 26% respectively.
ROC analysis for subjects in the 2-10 ng/mL PSA range (n=89)
Figure 2 ROC analysis for all subjects with PSA between 2 and 10 ng/mL (n=89) comparing PSA (AUC=0.52), %fPSA (AUC=0.53), %[-2]proPSA (AUC=0.72), and a composite logistic regression model combining PSA, BPSA, %fPSA, %[-2]proPSA, [-2]proPSA/BPSA and testosterone (more ...)