UC Berkeley

Background: Several deep learning-based techniques have been developed for prostate cancer (PCa) detection using multi-parametric MRI (mpMRI), but few of them have been rigorously evaluated relative to radiologists’ performance or whole-mount histopathology (WMHP).

Purpose: To compare the performance of a previously proposed deep learning algorithm, FocalNet, and expert radiologists in the detection of PCa on mpMRI with WMHP as the reference.

Study type: Retrospective, single-center study.

Subjects: 553 patients (development cohort: 427 patients; evaluation cohort: 126 patients) who underwent 3 T mpMRI prior to radical prostatectomy from October 2010 to February 2018.

Field Strength/Sequence: 3 T, T2-weighted imaging and diffusion-weighted imaging.

Assessment: FocalNet was trained on the development cohort to predict PCa locations by detection points, with a confidence value for each point, on the evaluation cohort. Four fellowship-trained genitourinary (GU) radiologists independently evaluated the evaluation cohort to detect suspicious PCa foci, annotate detection point locations, and assign a five-point suspicion score (1:least suspicious, 5:most suspicious) for each annotated detection point. The PCa detection performance of FocalNet and radiologists were evaluated by the lesion detection sensitivity versus the number of false-positive detections at different thresholds on suspicion scores. Clinically significant lesions: Gleason Group≥2 or pathological size≥10 mm. Index lesions: the highest Gleason Group and the largest pathological size (secondary).

Statistical tests:  Bootstrap hypothesis test for the detection sensitivity between radiologists and FocalNet.

Results: For the overall differential detection sensitivity, FocalNet was 5.1% and 4.7% below the radiologists for clinically significant and index lesions, respectively; however, the differences were not statistically significant (P=0.413 and P=0.282, respectively).

Data Conclusion: FocalNet achieved slightly lower but not statistically significant PCa detection performance compared to GU radiologists. Compared with radiologists, FocalNet demonstrated similar detection performance for a highly sensitive setting (suspicion score≥1) or a highly specific setting (suspicion score=5) while lower performance in between.