Tumor contact length: A novel multiparametric MRI predictor of prostate cancer outcomes.

Abstract

61 Background: Multiparametric MRI (MP-MRI) can visualize prostate tumors. MP-MRI characteristics (extraprostatic extension (ECE), tumor volume, etc.) can be predictive of final pathologic findings such as lymph node (LN) involvement, pathological ECE (pECE), and biochemical recurrence (BCR). These are pivotal in the decision-making process regarding treatment. Tumor contact length (TCL) is defined as the length of cancer in contact with the prostatic capsule. We evaluated the ability of MP-MRI determined TCL in predicting pECE, BCR and LN in patients undergoing radical prostatectomy. Methods: All patients who underwent a 3T MP-MRI at the NCI from 2007 to 2015 were retrospectively classed into no ECE, suspicious ECE (sECE) and frank ECE (fECE) based on MP-MRI findings. sECE was defined as tumor with capsular bulge on MRI while fECE was clear capsular obliteration and tumor extension beyond the prostatic capsule. Demographic data was obtained on patients with fECE and sECE on MP-MRI with the presence of pECE, LN, and BCR status following radical prostatectomy from a single surgeon (PP) experience. Chi-Square and Wilcoxon rank sum test were used to compare proportions and continuous variables respectively. Logistic regression was used to determine the predictive ability of TCL. Statistical significance was defined as p-value ≤0.05. Results: Of all 1,260 patients who underwent MP-MRI, we focused on 146 who had sECE (68) or fECE (78) on MP-MRI. Mean age was 60 years and median prostate specific antigen was 11.7 ng/ml. Logistic regression analysis showed that MP-MRI determined TCL was predictive of ECE (p=0.01), LN status (p=0.0001) on final pathology and BCR (p=0.05) during follow up. Patients with pECE had a longer median MP-MRI TCL (2.8 cm) compared to those without pECE (2.4 cm), p=0.04. When analyzed individually, fECE correlated with pECE (p=0.05) while s ECE did not correlate with pECE (p=0.11). Although, not statistically significant, the median MP-MRI TCL for sECE with pECE was still longer than in sECE with no pECE in the sub-group analysis. Conclusions: Longer TCL on MP-MRI can indicate presence of ECE, LN involvement at final pathology as well as predict BCR on follow up.