The 4Kscore Predicts the Grade and Stage of Prostate Cancer in the Radical Prostatectomy Specimen: Results from a Multi-institutional Prospective Trial

Background The 4Kscore accurately predicts aggressive prostate cancer (PCa) on prostate biopsy. Objective We assessed how well the 4Kscore predicts pathology at radical prostatectomy (RP). Design, setting, and participants Among 1312 men who prospectively underwent a 4Kscore and biopsy of the prostate at 26 sites throughout the United States from October 2013 to April 2014, we selected men who were diagnosed with cancer and underwent RP. Outcome measurements and statistical analysis The primary outcome was the presence of high-grade PCa or extracapsular extension. We assessed the association between the 4Kscore and the grade and extent of PCa at RP using the Wilcoxon rank sum test. We used logistic regression to investigate the added value of the 4Kscore in predicting a high-grade or non–organ-confined tumor when added to available postbiopsy clinical predictive tools. Results and limitations A total of 144 men were diagnosed with PCa and underwent RP. Higher 4Kscores were associated with higher grade at RP. For men with Gleason scores ≥6, 7, and 8 cancers in the surgical specimen, the median 4Kscores were 7% (interquartile range [IQR]: 4–2), 25% (IQR: 12–38), and 47% (IQR: 24–66) (p < 0.0001), respectively. The median 4Kscore among men with non–organ-confined cancer was significantly higher then men with organ-confined cancers (36% [IQR: 19–58] vs 19% [IQR: 9–35]; p = 0.002). The 4Kscore did not significantly add to available clinical prediction tools for determining the likelihood of a high grade or non–organ-confined cancer; however, we were limited by a small sample size for this analysis. Conclusions In a subset of men who underwent RP, the 4Kscore was significantly associated with pathologic grade and extracapsular extension in the surgical specimen, with higher scores associated with higher grade and more aggressive histology. The 4Kscore test may be helpful in selecting men who are likely to have adverse pathologic features at RP that may preclude them from being safely observed. Patient summary Among men with prostate cancer who underwent removal of the prostate, the 4Kscore was associated with the final grade and extent of cancer.