## 2 Materials and Methods
### Local Institutional Patient Population  
This was a HIPAA-compliant, IRB-approved retrospective study. The electronic medical records (EMR) were used to identify patients with prostatectomy and pre-operative prostate MR imaging between 2016-2020; 153 such patients were identified. These patients had MRIs that were interpreted by one of two abdominal radiologists (with 4 and 7 years of experience) using PIRADS version 2 criteria at the time of acquisition; PIRADS scores from the original MRI report were used in this study. Since whole-mount pathology-radiology correlation was unavailable at our institution, MRI exams, pre-surgical MR-US fusion-guided biopsy results, and final prostatectomy surgical pathology results were retrospectively reviewed by a single radiologist (SHM) to determine if the index cancer (defined as the dominant cancerous lesion with the highest GS in the gland) from the pathology report could be clearly localized and correlated with a reported MRI lesion. MRI lesions were only enrolled into the study if: (a) pre-surgical targeted MR-US fusion-guided biopsy of the lesion confirmed the lesion as the index \begin{table}
\begin{tabular}{c c c c} \hline \hline  & & **ProstateX-2** & **Local Institution** \\ \hline Patients & & & \\ \hline  & Mean age & 66.0 & 63.6 \\  & Range & 48–83 & 47–74 \\  & Race & NA & 51\% white, 44\% \\ MRI exams & & & \\ \hline  & _Total_ & \(n\) = 112 & \(n\) = 63 \\  & PIRADS 5 & NA & 25 \\  & PIRADS 4 & NA & 14 \\  & PIRADS 3 & NA & 2 \\  & PIRADS 2 & 0 & 22 \\ Lesion pathology & & & \\ \hline  & hrPCA & _Total_ & \(n\) = 35 (31\%) & \(n\) = 28 (44\%) \\  & & GG5 & 7 & 9 \\  & & GG4 & 8 & 4 \\  & & GG3 (4 + 3) & 20 & 15 \\  & \"Benign\" & _Total_ & \(n\) = 77 (69\%) & \(n\) = 35 (56\%) \\  & & GG2 (3 + 4) & 41 & 11 \\  & & GG1 & 36 & 2 \\  & & \textless{}GG1 & - & 22 \({}^{*}\) \\ Lesion zonal & & & \\ distribution & & & \\ \hline  & hrPCA & PZ & 15 & 22 \\  & & TZ & 20 & 6 \\  & \"Benign\" & PZ & 35 & 23 \\  & & TZ & 42 & 12 \\ \hline \hline \end{tabular}  
* AA: African American, GG: Gleason grade, PZ: peripheral zone, TZ: transitional zone.
* These were PIRADS 2 “pseudo-lesions” that were included to augment the benign subset of patients in the prostatectomy cohort from our institution. Biopsies were not performed, and these were presumed to be \textless{}GG1 based on stability of greater than two years in follow-up.  
\end{table} 
Table 1: Summary of patient demographics, MRI PIRADS scores, lesion Gleason grades, and lesion zonal distribution within the ProstateX-2 and local institutional datasets. cancer in the gland with lower GS and/or benign pathology in the rest of the targeted and systematic biopsies; and (b) surgical pathology report noted the index cancer to be within 1 GS of the targeted biopsy (to allow for minor up- and down-grading) and within the same side and relative location of the gland (anterior, posterior, lateral, base, mid, apex). Patients were excluded if: (a) MR-US fusion-guided biopsy demonstrated (i) >1 targeted lesion with the index cancer GS, or (ii) the presence of the index cancer GS in the systematic biopsy in areas non-adjacent to the MRI lesion; or (b) surgical pathology reported multifocal or bilateral areas of prostate cancer with the index cancer GS. Only one MRI lesion correlating with the gland's index cancer was enrolled from each prostate gland. These criteria lead to the identification of patients with a single or dominant ipsilateral lesion on MRI, with both biopsy and surgical pathology confirming the lesion and area as containing the index cancer, and the absence of other ipsilateral or contralateral lesions/areas with similar GS as the index cancer. Based on these stringent criteria, the index cancer of 41 of the 153 prostatectomy patients was confidently correlated with surgical pathology results and entered into this study. Tumor volume for the local dataset ranged from 0.00-82.90 cc (Mean 10.63 \(\pm\) 15.31).