Login to Access Video or Poster Abstract: MP04-12
Sources of Funding: None

Introduction

Nested variant (NV) urothelial cell carcinoma (UCC) is a rare histological subtype of UCC with benign features. There is limited data on the outcomes and characteristics of patients with this histology (largest study with 52 patients); however, it has traditionally been viewed as a more aggressive subtype of UCC and neoadjuvant chemotherapy is not recommended. Our primary interest was to assess whether there is a difference in overall survival (OS) after radical cystectomy (RC) between patients with NV features compared to patients with pure UCC.

Methods

We identified 1949 patients who underwent RC between January 1995 and December 2015 and had pure UCC or NV. We utilized a univariate and multivariable Cox proportional hazards model, adjusting for gender, positive lymph node invasion status, neoadjuvant chemotherapy, age and tumor stage at cystectomy to assess whether there was a difference in OS between UCC and NV patients. To determine whether there were differences in demographics and tumor characteristics between patients with NV and those without, group comparisons were made using Fisher’s exact test for categorical variables and Wilcoxon rank?sum test for continuous variables. Lastly we utilized the Cochran?Mantel?Haenszel method stratified on histology and applied the Breslow?Day test for homogeneity to evaluate whether there were differences in response to neoadjuvant chemotherapy based on histology.

Results

We identified 1807 (93%) pure UC patients and 142 (7.3%) patients with nested features. Among our 1949 patients, 919 with pure UCC and 77 with NV, died from any cause. The median follow up time for survivors was 4.6 years from RC. A larger proportion of NV patients at time of RC had lymph node invasion (p=0.007) and worse pathological tumor stage (p < 0.001) than pure UCC. On univariate analysis NV was associated with poorer OS (HR 1.26; 95% C.I. 1.00, 1.60; p = 0.049); however, on multivariable analysis, the association between histology and OS is no longer significant (HR 0.96; 95% CI 0.75, 1.22; p=0.7). We did not find a significant difference in response to neoadjuvant chemotherapy between the two histological groups (p = 0.6).

Conclusions

NV carcinoma presents at a higher stage than pure UCC at time of RC, but does not necessarily represent a more aggressive variant. It perhaps represents a delay in diagnosis due to NV benign features.

Funding

None