Index lesion contouring on prostate MRI for targeted MRI/US fusion biopsy-Evaluation of mismatch between radiologists and urologists

Purpose: Mistargeting of focal lesions due to inaccurate segmentations can lead to false-negative findings on MRI-guided targeted biopsies. The purpose of this retrospective study was to examine inter-reader agreement of prostate index lesion segmentations from actual biopsy data between urologists and radiologists. Method: Consecutive patients undergoing transperineal MRI-targeted prostate biopsy for PI-RADS 3-5 lesions between January 2020 and December 2021 were included. Agreement between segmentations on T2w-images between urologists and radiologists was assessed with Dice similarity coefficient (DSC) and 95 % Hausdorff distance (95 % HD). Differences in similarity scores were compared using Wilcoxon test. Differences depending on lesion features (size, zonal location, PI-RADS scores, lesion distinctness) were tested with Mann-Whitney U test. Correlation with prostate signal-intensity homogeneity score (PSHS) and lesion size was tested with Spearman's rank correlation. Results: Ninety-three patients (mean age 64.9 +/- 7.1y, median serum PSA 6.5 [4.33-10.00]) were included. Mean similarity scores were statistically significantly lower between urologists and radiologists compared to radiolo-gists only (DSC 0.41 +/- 0.24 vs. 0.59 +/- 0.23, p < 0.01; 95 %HD 6.38 +/- 5.45 mm vs. 4.47 +/- 4.12 mm, p < 0.01). There was a moderate and strong positive correlation between DSC scores and lesion size for segmentations from urologists and radiologists (rho = 0.331, p = 0.002) and radiologists only (rho = 0.501, p < 0.001). Similarity scores were worse in lesions <= 10 mm while other lesion features did not significantly influence similarity scores. Conclusion: There is significant mismatch of prostate index lesion segmentations between urologists and radi-ologists. Segmentation agreement positively correlates with lesion size. PI-RADS scores, zonal location, lesion distinctness, and PSHS show no significant impact on segmentation agreement. These findings could underpin benefits of perilesional biopsies.