A side-specific nomogram for extraprostatic extension may reduce the positive surgical margin rate in radical prostatectomy

Purpose: Nomograms predicting side-specific extraprostatic extension (EPE) may be applied to reduce positive surgical margin (PSM) rates in patients planned for radical prostatectomy (RP). This study evaluates the impact of implementing an externally validated nomogram for side-specific EPE on PSM rate and degree of nerve-sparing.

Methods: In patients planned for RP, the side-specific nomogram predictions (based on MRI, ISUP grade group, and PSA density), with an advised threshold of 20% for safe nerve-sparing, were presented preoperatively to the urological surgeon. The surgeon completed a survey before RP about the planning with respect to side-specific nerve-sparing and change of management due to the result of the nomogram. PSM rates and degree of nerve-sparing were compared to a retrospective control group treated in the months prior to the introduction of the nomogram.

Results: A total of 100 patients were included, 50 patients in both groups representing 200 prostate lobes. Of the patients, 37% had histologically confirmed EPE, and 40% a PSM. In 12% of the 100 lobes planned after nomogram presentation, a change in management due to the nomogram was reported. A per-prostate lobe analysis of all the lobes showed comparable rates of full nerve-sparing (45% vs. 30%; p = 0.083) and lower rates of PSM on the lobes with histological EPE (45% vs. 85%; p < 0.05) in the intervention (nomogram) group versus the control group.

Conclusion: Implementing a predictive nomogram for side-specific EPE in the surgical planning for nerve-sparing leads to lower rates PSM on the side of the histological EPE without compromising nerve-sparing.