Survival outcomes of micropapillary versus classic variant, loco-regional bladder cancer: A 2004-2019 National Cancer Database analysis.

Abstract

4592 Background: Micropapillary (MP) is a rare histologic variant of urothelial cancer (UC) with luminal-type characteristics and p53-like gene expression, leading to chemotherapy resistance and poor prognosis. However, contemporary outcomes of MP variant T2-T4, N0-N1 loco-regional bladder UC after definitive therapy are underreported, which this work sought to determine. Methods: A retrospective review was performed of all eligible cases of MP and classic UC (CUC) available during 2004-2019 from National Cancer Database. Socio-demographic, pathological, and clinical attributes were analyzed via descriptive and comparative statistics. Propensity-score matching was performed to adjust for baseline differences between MP and CUC. Overall survival, being the primary outcome, was compared using multivariable Cox proportional-hazards modeling and visualized through Kaplan-Meier curves. Results: 30072 cases of CUC and 397 of MP were identified. After propensity-score matching, 395 patients remained in both groups, with matched cohorts having no baseline differences in age, sex, race, Charlson-Deyo comorbidity index (CCI), insurance status, income, distance to hospital, hospital location, rural versus urban residence, tumor pathological grade, proportion receiving radiotherapy, and proportion getting regional lymph node surgery. In both matched cohorts there were 313 males (79%) and 82 females (21%). Both cohorts had 334 (85%) T2 cases, 41 (10%) T3 cases, and 20 (5%) T4 cases. Both cohorts had 375 (95%) N0 cases and 20 (5%) N1 cases. MP variant was associated with inferior survival compared to CUC (HR 1.26, 95%CI 1.03-1.54, P=0.024). Older age (≥65 years) and higher CCI were also associated with inferior survival. Irrespective of histology, patients undergoing surgery (S) plus chemotherapy (C) had better survival compared to S alone (HR 0.77, 95%CI 0.62-0.94, P=0.012). Regional lymph node surgery resulted in improved survival (HR 0.59, 95%CI 0.42-0.83, P=0.002). Sex, race, insurance, income, and hospital type did not impact survival. Median and two-year OS are summarized. Conclusions: Survival outcomes of MP are poorer than CUC of bladder. Surgery combined with perioperative chemotherapy was associated with better survival compared to surgery alone in patients with MP and CUC. Studies evaluating novel immunotherapies and antibody drug conjugates in perioperative setting are needed to improve outcomes. [Table: see text]