Abstract Objective The study aims to identify the optimal 4Kscore thresholds to determine the need for a prostate biopsy when multiparametric magnetic resonance imaging (MRI) (mpMRI) is negative or indeterminate. Materials and methods We analysed retrospective data from men in eight different institutions who underwent an mpMRI, 4Kscore and prostate biopsy for evaluation of prostate cancer. We selected men with a negative (PIRADS ≤2) or indeterminate (PIRADS 3) mpMRI. 4Kscore values were categorized into ranges of 1–7, 8–19, 20–32 and greater than 32. We evaluated the proportion of men with grade group 2 or higher (GG2+) cancer in groups defined by PIRADS and 4Kscore. We also evaluated the number of biopsies avoided and GG2+ cancer missed in each group reported depend on 4Kscore cutoff points. Results Among 1111 men who had an mpMRI, 4Kscore and biopsy, 625 of them had PIRADS ≤3 on mpMRI: 374 negative (PIRADS ≤2) and 251 indeterminate (PIRADS 3). In men with a negative mpMRI, we found a 4Kscore cut‐point of 33 resulted in an increased risk of GG2+ cancer on biopsy. In patients with an equivocal lesion on mpMRI, men with a 4Kscore cutoff ≥8 had a greater risk of GG2+ cancer on biopsy. Decision curve analysis supported the proposed cut‐points in each mpMRI group. Conclusions In men with negative and indeterminate mpMRI, we found the best 4Kscore threshold to determine the need for biopsy to be 33 and 8 respectively. Future prospective studies in independent populations are needed to confirm these findings.
