Implications of micropapillary urothelial carcinoma variant on prognosis following radical cystectomy: A multi-institutional investigation

To determine the association of micropapillary urothelial carcinoma (MUC) variant histology with bladder cancer outcomes after radical cystectomy. Information on MUC patients treated with radical cystectomy was obtained from five academic centers. Data on 1,497 patients were assembled in a relational database. Tumor histology was categorized as urothelial carcinoma without any histological variants (UC; n = 1,346) or MUC (n = 151). Univariable and multivariable models were used to analyze associations with recurrence-free (RFS) and overall (OS) survival. Median follow-up was 10.0 and 7.8 years for the UC and MUC groups, respectively. No significant differences were noted between UC and MUC groups with regard to age, gender, clinical disease stage, and administration of neoadjuvant and adjuvant chemotherapy (all, P ≥ 0.10). When compared with UC, presence of MUC was associated with higher pathologic stage (organ-confined, 60% vs. 27%; extravesical, 18% vs. 23%; node-positive, 22% vs. 50%; P < 0.01) and lymphovascular invasion (29% vs. 58%; P < 0.01) at cystectomy. In comparison with UC, MUC patients had poorer 5-year RFS (70% vs. 44%; P < 0.01) and OS (61% vs. 38%; P < 0.01). However, on multivariable analysis, tumor histology was not independently associated with the risks of recurrence (P = 0.27) or mortality (P = 0.12). This multi-institutional analysis demonstrated that the presence of MUC was associated with locally advanced disease at radical cystectomy. However, clinical outcomes were comparable to those with pure UC after controlling for standard clinicopathologic predictors.