Adding a Coefficient for Race to the 4Kscore Improves Calibration for Black Men

Abstract

Purpose: Black men face a higher incidence of high-risk prostate cancer (PCa) compared with non-Black men. While the 4Kscore is a widely utilized commercial test for PCa risk assessment, it does not currently account for racial differences. The aim of this study is to describe and validate a prespecified race coefficient for the 4Kscore with the goal of improving the accuracy of this test for Black men.

Materials and methods: Using data from 85 Black men from the initial US prospective validation study, a race coefficient of 0.6 on the log-odds scale was prespecified. We calculated discrimination, calibration, and clinical utility of the 4Kscore with and without this coefficient for Black race in our primary analysis cohort of 205 Black men undergoing biopsy for PCa in a Veterans Affairs (VA) institution. We performed a sensitivity analysis using a combined cohort from the US prospective validation and the VA studies.

Results: The mean probability of high-grade PCa from the 4Kscore in the primary cohort increased from 25% to 37% with race coefficient addition. Incorporating the race coefficient improved 4Kscore's calibration in Black men, with consequent improvements in clinical utility based on decision curve analysis. Model discrimination was maintained (AUC 0.825 vs 0.828, P = .14) in the combined cohort of Black and non-Black men from the US prospective and VA studies and the calibration remained largely unchanged.

Conclusions: Incorporating a prespecified coefficient for Black race improved calibration and clinical utility of the 4Kscore among Black men and should be added to the 4Kscore.

Keywords: African Americans; biomarkers; prostate neoplasm.

Figure 1.

Calibration of the 4Kscore before and after application of the race coefficient A) represents calibration before and after the race coefficient adjustment in 205 men in the VA cohort. B) represents calibration before and after race coefficient in black men from both cohorts (N= 290). C) represents calibration before and after race coefficient in all men in both studies (N=1,378). A calibration curve slope of 45 degrees is ideal.

Figure 1.

Calibration of the 4Kscore before and after application of the race coefficient A) represents calibration before and after the race coefficient adjustment in 205 men in the VA cohort. B) represents calibration before and after race coefficient in black men from both cohorts (N= 290). C) represents calibration before and after race coefficient in all men in both studies (N=1,378). A calibration curve slope of 45 degrees is ideal.

Figure 2.

Decision curve analysis of 4Kscore among primary validation cohort (VA cohort) Explanation for net benefit: Curve with highest net benefit at any biopsy threshold results in best clinical results. Red curve represents biopsy in all patients. Green curve represents biopsy in no patients. Purple curve represents biopsy decision using the 4Kscore without race coefficient. Blue curve presents biopsy decision using 4Kscore with race coefficient.