Chemotherapy with significant mortality benefit in patients with bladder cancer with variant and non-urothelial histologies (NUVH).

Abstract

4586 Background: Non urothelial cancers and urothelial cancers with variant histologies(NUVH) have a more aggressive natural history and are at a higher risk of progression to muscle invasive disease(MIBC) when compared to their urothelial counterparts. Although surgical resection is the treatment of choice in localized disease, radiation(RT) is commonly used in patients who are not surgical candidates. The use of chemotherapy has shown modest benefit in some retrospective studies. Considering the low incidence of NUVH, there are no large-scale studies examining the benefits of chemoradiation(CRT) in MIBC with NUVH. Methods: The National Cancer Database was queried to identify MIBC patients with NUVH from the years 2004-2018.Inclusion criteria for the study are age > 18 years, Non urothelial or variant histologies and receipt of RT. Patients who underwent cystectomy or had metastatic disease were excluded. The population was divided into two cohorts if they received chemoradiation. Chi-Square test and Mann Whitney U tests were used to compare frequency distributions. Cox proportional Hazard regression was employed to control for confounding factors associated with overall survival. Covariates for confounding included age, race, sex, income, insurance status, charlson-deyo comorbidity index, education. Results: Among 1773 observations in the final analysis, 63.05%(n = 1118) received CRT. Small cell, large cell and neuroendocrine cancers composed of the majority of NUVH. 38.01% (n = 641). Other histologies composed of squamous cell cancer 30.34%(n = 538), spindle cell/sarcomatoid cancers10.15%(180), adenocarcinoma 11.44%(203). Patients who received CRT were found to be significantly younger (76 vs 82 years P: < 0.0001) with higher male predominance74.73%. 5 year overall mortality was significaantly lower in the CRT vs RT group ( 66.47% vs 81.55%, p < 0.001). After controlling for confounding factors, CRT was associated with lower risk of mortality Hazard Ratio(HR)of 0.41(0.36-0.47) p < 0.0001. Added, the survival benefit of CRT continued in the non small cell variant cohort HR: 0.43(0.37-0.51) P < 0.0001. Conclusions: In this large retrospective study, CRT was associated with reduced overall mortality among patients with non-urothelial MIBC. The findings suggest the importance of systemic therapy in providing a survival advantage to non-urothelial MIBC, including the non-small cell variants. [Table: see text]