Observational study comparing the accuracy/variability between the ERSPC and the PCPT risk calculators for the prediction of significant prostate cancer in patients with PSA <10 ng/mL

Abstract

Introduction: Risk calculators (RCs) are easy-to-use tools considering available clinical variables that could help to select those patients with risk of prostate cancer (PCa) who should undergo a prostate biopsy.

Objective: To perform a comparison for the prediction of significant PCa (SigPCa) between the European Randomised Study of Screening for PCa (ERSPC) and the PCa Prevention Trial (PCPT) RCs in patients with prostate-specific antigen (PSA) between 3 and 10 ng/mL through an evaluation of the accuracy/variability between two consecutive PSA values.

Setting: An observational study in a major university hospital in the south of Spain.

Methods and participants: An observational study was performed in patients who underwent a prostate biopsy. SigPCa probabilities were calculated with the two PSA measures using ERSPC3/4+digital rectal examination and PCPT v2+free PSA RCs. The prediction of SigPCa was determined by the area under the receiver operating characteristic curve (AUC). Calibration, discrimination and decision curve analysis were studied. The variability between both RCs' agreement was compared using Cohen's kappa coefficient.

Results: 510 patients were analysed (87 diagnosed with SigPCa). The median PSA values were 5.3 and 5 ng/mL for PSA1 and PSA2, respectively. Both RCs overestimated the risk in the case of high-risk probabilities. Discriminative ability for SigPCa was similar between models with an AUC=0.73 (0.68-0.79) for ERSPC-RC versus 0.73 (0.67-0.79) for PCPT-RC. ERSPC-RC showed less variability than PCPT-RC, with a constant agreement (k=0.7-0.8) for usual range of clinical decision-making. Remarkably, a higher number of biopsies would be avoided using the ERSPC-RC, but more SigPCa would be missed along all the risk probabilities.

Conclusions: Both RCs performed similar in the prediction of SigPCa. However, ERSPC-RC seems to be more stable for intraindividual PSA variations.

Keywords: ERSPC; PCPT; risk calculator variability; significant prostate cancer.

Figure 1

Receiver operating characteristic curves and area under the curve (AUC) values: (A) for the ERSPC1-RC (black) and PCPT1-RC (grey) for SigPCa; (B) for the ERSPC1-RC and the ERSPC2-RC for positive biopsy; (C) for the PCPT1-RC and the PCPT2-RC for positive biopsy; (D) for the ERSPC2-RC and the PCPT2-RC for SigPCa. HG, high grade; PB, positive biopsy.

Figure 2

Calibration plots for risk estimation, showing the agreement between predicted risk (horizontal axis) and the actual observed prevalence for people with that risk (vertical axis). The diagonal line shows the ideal behaviour of a perfectly calibrated risk calculator, separating the upper left region where risks are underestimated from the lower right, where they are overestimated. (A) Calibration plots for ERSPC1-RC SigPCa risk estimation. (B) Calibration plots for PCPT1-RC SigPCa risk estimation. PCa, prostate cancer; SigPCa, significant PCa.

Figure 3

Results of the decision curve analysis. (A) Net benefit for the prediction of SigPCa on biopsy using the ERSPC1-RC (black line) and the PCPT1-RC (grey line) as a function of the risk threshold, compared with those benefits of the strategies of treating all patients (dashed line) and treating none (thin line). (B) Plot demonstrating net reduction of interventions per 100 patients using the ERSPC-RC (black line) and the PCPT-RC (grey line). ERSPC, European -Randomised Study of Screening for PCa; PCPT, PCa Prevention- Trial.

Figure 4

Graphics showing Cohen’s κ coefficient, which evaluated the agreement between risk calculators, as a function of the decision threshold, with 1 being total agreement and 0 being the worst possible expected agreement between rates. (A) Agreement between ERSPC1-RC and ERSPC2-RC for significant prostate cancer (SigPCa). (B) Agreement between PCPT1-RC and PCPT2-RC for SigPCa. (C) Agreement between ERSPC1-RC and PCPT1-RC for SigPCa.

Figure 5

Graphics showing sensitivities and specificities of both risk calculators along the clinically useful risk threshold. The ERSPC-RC (black line) and the PCPT-RC (grey line). ERSPC, European -Randomised Study of Screening for PCa; PCPT, PCa Prevention- Trial.