Quantification of micropapillary component on transurethral resection is associated with likelihood of occult lymph node metastasis at radical cystectomy

Abstract

Introduction/background: Micropapillary variant urothelial carcinoma (MPUC) is associated with increased risk of treatment failure with intravesical therapy likely due to the increased risk of occult lymph node (LN) metastasis at radical cystectomy (RC). To date, limited data exists as to whether percent MPUC present within transurethral resection (TUR) samples impacts LN positivity at RC. Our objective is to evaluate the association of percentage MP variant on TUR on incidence of lymph node metastasis and survival outcomes.

Methods: A total of 67 patients with MPUC on TUR were identified from a prospectively maintained database of patients undergoing RC at our institution between 2007 and 2022. TUR samples were rereviewed by an expert GU pathologist with over ten years of experience. Presence and percent MP component, LVI, CIS, grade, and clinical stage were evaluated. Pathologic outcomes were collected from subsequent RC specimens, and recurrence free (RFS) and overall survival (OS) were estimated via the Kaplan-Meier method. Associations between percent MP and lymph node metastasis, RFS, and OS were assessed with univariate and multivariable logistic regression and Cox survival analyses as appropriate.

Results: Thirty four of 67 (51%) patients underwent RC for cT1 disease, the remainder harbored ≥cT2 disease. 19 of 33 (58%) patients with ≥cT2 disease received neoadjuvant chemotherapy (NAC). Mean percent MPUC was 35% in cT1 patients and 28% in cT2 patients (P = 0.25). On univariate analysis, both MPUC ≥ 30% (Odds Ratio (OR) 3.38, P = 0.02) and clinical ≥T2 (OR 2.88, P = 0.04) were significant predictors of nodal metastasis at RC. On multivariable analysis, MPUC% (OR 1.02, P = 0.036) or MPUC% ≥ 30% (OR 4.01, P = 0.013) and clinical T stage ≥2 (OR 3.73, P = 0.018) were significant predictors of pathologic node positive disease. The lowest rate of LN metastasis was found in patients with cT1 disease and MPUC <30% (3/16, 18.7%), versus the highest in ≥cT2 disease and MP ≥ 30% (12/16, 75%).

Conclusions: Percent MPUC component on TUR is associated with increased risk of occult lymph node metastasis at RC. Routine pathologic evaluation of percent MP component has the potential to help select patients with MPUC that might be reasonable candidates for intravesical therapy.

Keywords: Bladder Cancer; Micropapillary Variant; Pathologic quantification; Urothelial carcinoma; Variant Histology.