PD12-10 MANAGEMENT OF VARIANT HISTOLOGY IN NON-MUSCLE INVASIVE BLADDER CANCER

Abstract

INTRODUCTION AND OBJECTIVE: Histologic variants in non-muscle invasive bladder cancer (NMIBC) have been associated with a worse prognosis compared to pure urothelial carcinoma (PUC), however it is unclear if modern classification of histologic variants has the same clinical significance as seen in prior studies. The purpose of this study is to determine if variant histology in a contemporary cohort of NMIBC patients is associated with a higher recurrence rate after intravesical treatment with Bacillus Calmette-Guérin (BCG) compared to PUC. METHODS: We reviewed the charts of patients with high grade Ta or T1 bladder tumor pathology obtained from transurethral resection of bladder tumor (TURBT) and reviewed by Stanford Health Care between January 2013 and March 2018. Exclusion criteria included lack of follow up, muscle-invasive disease on restaging TURBT, and lack of pathology review at Stanford. Patients with variant histology were compared to patients with PUC, and the primary outcome measured was 2-year recurrence-free survival after treatment with intravesical BCG. Statistical analysis was performed with SAS, and Kaplan-Meier curves with statistical analysis were generated with Prism. RESULTS: Of the 347 patients evaluated in this study, 59 patients had variant histology and 288 patients had PUC, with mean follow up of 1.9 and 2.1 years, respectively. Of the patients with variant histology, 14 (23.7%) patients had more than one variant present. The remaining histologic variants consisted of squamous (9, 15.3%), glandular (8, 13.6%), micropapillary (7, 11.9%) plasmacytoid (7, 11.9%), sarcomatoid (6, 10.2%), nested (3, 5.1%), adenocarcinoma (2, 3.4%), lipid rich (1, 1.7%), giant cell (1, 1.7%), and trophoblastic (1, 1.7%). Patients received BCG in 35/59 (59.3%) variant histology cases and 213/288 (74.0%) PUC cases (p=0.023). Recurrence-free survival after treatment with BCG at 2 years was greater in the variant histology group compared to the PUC group (62.1% vs 38.0%, p<0.05). Multivariate analysis demonstrated better 2-year recurrence-free survival rates for variant histology patients (HR 0.43, 95% CI 0.25-0.73) when adjusting for T stage, presence of carcinoma in situ, treatment with maintenance BCG, recurrent bladder tumors, and treatment by the referring provider. CONCLUSIONS: In contrast to prior studies, our study demonstrates that NMIBC with variant histology treated with BCG had better 2-year recurrence-free survival compared to PUC. Our findings suggest that a select subgroup of patients with NMIBC with variant histology may benefit from treatment with BCG. Source of Funding: None