BackgroundTo explore the value of a multiparametric magnetic resonance imaging (MRI)-based deep learning model for the preoperative prediction ofKi67expression in prostate cancer (PCa).MaterialsThe data of 229 patients with PCa from two centers were retrospectively analyzed and divided into training, internal validation, and external validation sets. Deep learning features were extracted and selected from each patient’s prostate multiparametric MRI (diffusion-weighted imaging, T2-weighted imaging, and contrast-enhanced T1-weighted imaging sequences) data to establish a deep radiomic signature and construct models for the preoperative prediction ofKi67expression. Independent predictive risk factors were identified and incorporated into a clinical model, and the clinical and deep learning models were combined to obtain a joint model. The predictive performance of multiple deep-learning models was then evaluated.ResultsSeven prediction models were constructed: one clinical model, three deep learning models (the DLRS-Resnet, DLRS-Inception, and DLRS-Densenet models), and three joint models (the Nomogram-Resnet, Nomogram-Inception, and Nomogram-Densenet models). The areas under the curve (AUCs) of the clinical model in the testing, internal validation, and external validation sets were 0.794, 0.711, and 0.75, respectively. The AUCs of the deep models and joint models ranged from 0.939 to 0.993. The DeLong test revealed that the predictive performance of the deep learning models and the joint models was superior to that of the clinical model (p< 0.01). The predictive performance of the DLRS-Resnet model was inferior to that of the Nomogram-Resnet model (p< 0.01), whereas the predictive performance of the remaining deep learning models and joint models did not differ significantly.ConclusionThe multiple easy-to-use deep learning–based models for predictingKi67expression in PCa developed in this study can help physicians obtain more detailed prognostic data before a patient undergoes surgery.