We investigated whether local extension findings on preoperative MRI and excisional pathology are associated with positive surgical margin and biochemical recurrence after robot-assisted radical prostatectomy.

We identified 704 of our patients that underwent robot-assisted radical prostatectomy between 2012 and 2020, and extracted the 326 patients who had preoperative MRI scans and a radiologist reading. These patients were classified into groups according to the presence of local extension on MRI and pathological findings: ≤ cT2pT2 (195 cases), ≤ cT2pT3 (55 cases), cT3pT2 (31 cases), and cT3pT3 (45 cases). We compared positive surgical margin and biochemical recurrence between them.

Median age was 69 years, positive surgical margin rate was 20.2%, and five-year biochemical recurrence rate was 20.3%. Of the 226 patients without local invasion on excisional pathology, those with local extension on MRI (cT3pT2) had relatively higher positive surgical margin rate (29.0% vs. 14.4%, p = 0.05) and significantly higher five-year biochemical recurrence rate (25.8% vs. 9.3%, p = 0.01) than those without local extension on MRI (≤ cT2pT2). Similarly, among the 100 patients with local extension on excisional pathology, those with cT3pT3 had relatively higher positive surgical margin (37.8% vs. 21.8%, p = 0.08) and significantly higher five-year biochemical recurrence (53.3% vs. 29.3%, p = 0.01) than those with ≤ cT2pT3. In multivariate analysis, local extension on MRI was an independent predictor of biochemical recurrence (OR 2.1, 95%CI 1.1–3.9, p = 0.01).

Local extension on MRI is a prognostic factor independent of pathological stage. The use of MRI may complement the prognostic value of excisional pathology of prostate cancer.