MRI‐Determined Tumor Contact Area as a Predictor of Pathological Extraprostatic Extension in Clinical T2 Prostate Cancer

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Abstract
Objectives: To assess the validity of magnetic resonance imaging‐determined tumor contact area (MRI‐TCA) as a predictive factor for pathological extraprostatic extension (EPE) in cT2N0M0 prostate cancer patients. Methods: We retrospectively analyzed 72 cT2N0M0 prostate cancer patients who underwent multiparametric MRI (mpMRI) followed by robot‐assisted laparoscopic prostatectomy (RARP) between February 2014 and April 2021. Patients whose MRI‐based index lesion did not match the pathological specimens were excluded. MRI‐TCA was approximated using an elliptical shape and calculated by two different methods: MRI‐TCA1: Calculated using the tumor contact length (TCL) in the axial plane and the longer TCL in either the sagittal or coronal plane, capturing tumor dimensions across two planes. MRI‐TCA2: Calculated using the TCL in the axial plane and tumor thickness derived from MRI slice data, reflecting the tumor’s contact area within the MRI volume. We compared postoperative prostate‐specific antigen (PSA) recurrence‐free survival by stratifying patients based on the optimal thresholds of MRI‐TCL, MRI‐TCA1, MRI‐TCA2, pathological‐TCL, and pathological‐TCA. Results: Sixteen patients (22.2%) were pathologically positive for EPE. MRI‐TCL, MRI‐TCA1, and MRI‐TCA2 were significantly greater in patients with EPE‐positive (EPE+) tumors than in those with EPE‐negative (EPE−) tumors ( p < 0.0001, p < 0.0001, and p = 0.0026, respectively). No statistically significant differences were found between MRI‐TCL and MRI‐TCA1 ( p = 0.914) or between MRI‐TCL and MRI‐TCA2 ( p = 0.112) in predicting pathological EPE. A significant difference in postoperative PSA recurrence rate was observed in the stratified analysis based on pathological‐TCA ( p = 0.022). Conclusion: Both MRI‐TCA1 and MRI‐TCA2 are clinically accessible and effective parameters for predicting pathological EPE in cT2N0M0 prostate cancer patients. However, neither method demonstrated clear superiority over MRI‐TCL. Pathological‐TCA was shown to be a significant predictor of both pathological EPE and postoperative PSA recurrence.

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