Index tumor volume on MRI as a predictor of clinical and pathologic outcomes following radical prostatectomy

Purpose Index tumor volume (ITV) measured on radical prostatectomy (RP) specimens has been shown to be associated with adverse pathologic and oncologic outcomes. We evaluate the value of ITV calculated from prostate multiparametric MRI (mpMRI) in predicting adverse clinical and pathologic outcomes. Materials and methods Data from a prospectively maintained, single-institution database were analyzed for patients who underwent mpMRI prior to RP (2007–2016). Index tumor was defined as a T2-visible lesion with the longest diameter. Adverse pathologic outcomes were extraprostatic extension (EPE), lymph node invasion (LNI), seminal vesicle invasion (SVI), and positive margins (PM). Logistic and Cox proportional hazard regression were used to assess associations with adverse pathology and biochemical recurrence (BCR), respectively. Results Of the 455 patients included, EPE, LNI, SVI and PM were present in 23.5%, 6.2%, 5.5% and 15.7% patients, respectively. Patients with adverse pathologic outcomes had larger median ITV. ITV was found to be an independent predictor of EPE (OR 1.22, p = 0.010), LNI (OR 1.39, p = 0.001), and SVI (OR 1.28, p = 0.009), but not PM (OR 1.03, p = 0.522). Combination of ITV and PSA was found to have predictive ability comparable to that of modified Partin tables (EPE:ITV + PSA AUC = 0.71 vs. Partin AUC = 0.71; LNI:ITV + PSA AUC = 0.92 vs. Partin AUC = 0.90, SVI:ITV + PSA AUC = 0.78 vs. Partin AUC = 0.82). 5 year BCR-free survival (median follow-up 24.9 months) was higher for patients with ITV < 2 cc (84.1% vs. 58.5%, p = 0.001). However, ITV was not found to be an independent predictor of BCR (HR 1.69, p = 0.130). Conclusions We demonstrate that ITV measured on mpMRI is a predictor of adverse pathologic and clinical outcomes and can aid in preoperative risk assessment.