Association of early bone metastases and outcomes of the bone predominant metastatic urothelial carcinoma (BP mUC) phenotype.

Abstract

e16016 Background: Prior analyses demonstrated worse outcomes with the BP mUC clinical phenotype. UC molecular subtypes that may correlate with the BP phenotype have been defined, however molecular subtyping is not a readily available standard practice. We hypothesized that BP mUC has worse prognosis vs. non-BP (NBP) mUC and evaluated patient (pt) characteristics associated with the mUC subtype, responses and outcomes. Methods: We searched the electronic medical record (EMR) to identify pts with mUC who received systemic therapy in the metastatic setting. Demographic, clinicopathologic, treatment (trt), response, progression-free survival (PFS), overall survival (OS ) from start of first line trt. Imaging was reviewed to identify NBP or BP disease. Logistic regression, Cox proportional-hazards and Kaplan-Meier analyses were performed. Results: 149 mUC pts were identified (64% male, 68% smokers ), median age at 1st line trt was 68 years. 70% had de-novo mets, 46% to lung and 27% to liver. 22% of pts were BP, of these, 36% were de-novo metastatic. In non- de-novo metastatic pts (70% of pts), first progression of disease to bone was associated with development of the BP phenotype (OR = 30.46, 95% CI 6.37 to 145.61; p < 0.0001). BP pts had higher rate of death (HR = 2.28, 95% CI 1.45 to 3.58, p = 0.0004), shorter PFS from 1st line trt, (11.7 vs 14.9 weeks, p = 0.032) as well as shorter OS from 1st line trt (24.6 vs 56.6 weeks, p = 0.002) compared to NBP pts. There was no difference in PFS between BP and NBP groups for pts treated with 1st line platinum-based chemotherapy (11.8 vs 18.3 weeks, p = 0.091) or for BP pts treated with 1st line immunotherapy vs platinum-based chemotherapy (11.71 vs 11.86 weeks, p = 0.135). Conclusions: Early bone metastases are associated with the development of the BP metastatic phenotype. BP pts have worse PFS and OS from 1st line trt compared to NBP pts. PFS remains poor when BP pts are treated with either platinum-based chemotherapy or immunotherapy in the first line setting. Imaging to determine the presence of bone metastases may routinely be pursued and careful attention paid on follow up imaging. Clinical trials and prospective registries focusing on efficacy endpoints for BP mUC are needed.