Quantification of median lobe protrusion and its impact on the base surgical margin status during robot-assisted laparoscopic prostatectomy.

PURPOSE: Protrusion of the median lobe (PML) is thought to add technical difficulty during robot-assisted laparoscopic prostatectomy (RALP). Thus, we quantified PML using preoperative magnetic resonance imaging (MRI) and evaluated its impact on base surgical margin (BSM) status during RALP. METHODS: The clinical data of consecutive patients who underwent RALP were retrieved from a prospectively registered database. Of the 655 eligible men, 9 patients were excluded because they did not undergo MRI. PML was measured in a T2-weighted mid-sagittal scan. We performed univariate and multiple logistic regression analyses. RESULTS: The mean PML was 8.3 ± 3.6 mm. The rate of positive surgical margins was 17.3 % (73/423) in pathologic stage T2 and 34.6 % (226/646) in all cases. The BSMs were positive in 10.1 % (66/646) of cases. A logistic regression analysis revealed that PML was significantly correlated with BSM positivity in all cases (odds ratio [OR] 1.080, p = 0.026). In particular, they had a stronger correlation with pathologic stage T3 or higher (OR 1.1143, p = 0.004). PML was an independent predictor of BSM positivity (OR 1.113, p = 0.046) in pathologic stage T3 or higher, as were preoperative prostate-specific antigen, prostate size, and pathologic stage. Cases with 10 mm or higher PML had significantly more BSM positivity than cases with <10 mm PML (35.9 vs. 20.1 %, p = 0.012). CONCLUSIONS: Protrusion of the median lobe measured using preoperative MRI was significantly correlated with positive BSMs during RALP. Surgeons should pay more attention to patients with 10 mm or higher PML and advanced stages.