External validation of a nomogram for unilateral pelvic lymph node dissection in prostate cancer

To explore the rationale of unilateral extended pelvic lymph node dissection (ePLND) during radical prostatectomy (RP) by external validation of a nomogram for unilateral ePLND (unilat-NG) and comparison to the Briganti 2019 nomogram.

Patients with magnetic resonance imaging-fusion biopsy and consecutive RP with bilateral ePLND were identified within an institutional database. The primary endpoint was the detection rate of lymph node invasion (LNI) contralateral to the prostatic lobe with adverse cancer characteristics. The performance of the unilat-NG and the Briganti 2019 nomogram to detect contralateral LNI was assessed using descriptive analysis, the receiver operating characteristic curve-derived area under the curve (AUC), and multivariable logistic regression analyses.

Of the overall 406 consecutive patients, 68/406 (16.7%) presented with pathological (p)N1 disease at RP. The AUC for the unilat-NG with a 1%, 2% and 2.5% cut-off was 0.58 (95% confidence interval [CI] 0.53-0.63), 0.67 (95% CI 0.59-0.75), and 0.69 (95% CI 0.60-0. 77), respectively; compared to an AUC of 0.72 (95% CI 0.66-0.78) for the Briganti 2019 nomogram with a 7% cut-off. Applying the unilat-NG with a 2.5% cut-off, contralateral ePLND could be omitted in 303/406 (74.6%) patients, misclassifying 10/406 (2.5%) patients with pN0 disease.

The Briganti 2019 nomogram outperformed the novel unilat-NG in contralateral LNI prediction. Yet, a significant proportion of patients undergoing unilateral ePLND would be falsely classified with pN0 disease using any of the nomograms. Therefore, bilateral ePLND should remain the standard of care if PLND is indicated.