目的: 评估前列腺影像报告和数据评分系统(prostate imaging reporting and data system，PI-RADS)中将病灶最大径15 mm作为4分升级为5分标准的合理性并进行改良，以提升对临床有意义前列腺癌(clinical significant prostate cancer，csPCa)的预测效果。方法: 回顾性分析北京大学第一医院2019—2022年间接受前列腺MRI检查及穿刺的患者，将这组患者作为训练集，2023年的患者作为验证集，对病灶进行定位及测量最大径。采用受试者操作特征(receiver operating characteristics，ROC)曲线计算出病灶最大径预测csPCa的曲线下面积(area under curve，AUC)及最佳截断值，采用倾向性评分匹配(propensity score matching, PSM)缩小组间差异，在验证集中进行诊断效能的比较。结果: 训练集的589例患者中，358例(60.8%)的病灶位于外周带，231例(39.2%)位于移行带，496例(84.2%)为csPCa病变。外周带病灶的中位直径小于移行带病灶(14 mm vs. 19 mm，P < 0.001)。ROC分析最大径对csPCa的预测效果，外周带病灶(AUC=0.709)与移行带病灶(AUC=0.673)相比差异无统计学意义(P=0.585)，计算得出外周带病灶的截断值为11.5 mm，移行带病灶为16.5 mm。通过在验证集中计算截断值对应的约登指数(Youden index)，发现按病灶位置进行分层可以取得更好的预测效果，计算净重新分类指数(net reclassification index, NRI)为0.170。结论: 将15 mm作为病灶PI-RADS评分4分升级为5分的标准过于笼统，外周带病灶的截断值小于移行带病灶，应考虑对不同位置的病灶分开设定截断值。

Objective: To assess the rationality of the maximum lesion diameter of 15 mm in prostate imaging reporting and data system (PI-RADS) as a criterion for upgrading a lesion from category 4 to 5 and improve it to enhance the prediction of clinically significant prostate cancer (csPCa). Methods: In this study, the patients who underwent prostate magnetic resonance imaging (MRI) and prostate biopsy at Peking University First Hospital from 2019 to 2022 as a development cohort, and the patients in 2023 as a validation cohort were reviewed. The localization and maximum diameter of the lesion were fully evaluated. The area under the curve (AUC) and the cut-off value of the maximum diameter of the lesion to predict the detection of csPCa were calculated from the receiver operating characteristics (ROC) curve. Confounding factors were reduced by propensity score matching (PSM). Diagnostic efficacy was compared in the validation cohort. Results: Of the 589 patients in the development cohort, 358 (60.8%) lesions were located in the peripheral zone and 231 (39.2%) were located in the transition zone, and 496 (84.2%) patients detected csPCa. The median diameter of the lesions in the peripheral zone was smaller than that in the transition zone (14 mm vs. 19 mm, P < 0.001). In the ROC analysis of the maximal diameter on the csPCa prediction, there was no statistically significant difference between the peri-pheral zone (AUC=0.709) and the transition zone (AUC=0.673, P=0.585), and the cut-off values were calculated to be 11.5 mm for the peripheral zone and 16.5 mm for the migrating zone. By calcula-ting the Youden index for the cut-off values in the validation cohort, we found that the categorisation by lesion location led to better predictive results. Finally, the net reclassification index (NRI) was 0.170. Conclusion: 15 mm as a criterion for upgrading the PI-RADS score from 4 to 5 is reasonable but too general. The cut-off value for peripheral zone lesions is smaller than that in transitional zone. In the future consideration could be given to setting separate cut-off values for lesions in different locations.