Role of consolidative radiotherapy for metastatic urothelial bladder cancer patients without progression and with no more than five residual metastatic lesions following first line systemic therapy: A retrospective analysis.

Abstract

454 Background: Consolidative local treatment of the primary tumor and metastases in the treatment of metastatic malignancies has shown promising results in several types of primary tumors. The aim of this study is to assess consolidative radiotherapy to the bladder and to residual metastases among metastatic urothelial bladder cancer with no progression following first line systemic therapy, hypothesizing an increase in overall survival and in progression free survival. Methods: Between January 2005 and December 2018, patients who received standard first-line chemotherapy for the treatment of metastatic urothelial bladder cancer (mUBC) were retrospectively identified through the database of four Comprehensive Cancer Centers in France. Among them, patients with no disease progression following chemotherapy and with no more than 5 residual metastases were analyzed: patients who received subsequent radiotherapy (of EQD2Gy > 50Gy) to the bladder and residual metastases were included in the consolidative group (RT group), and the other patients were included in the observation group (OBS group). PFS and OS were determined from the start of the first-line chemotherapy using the Kaplan-Meier method. To account for the delay from chemotherapy initiation to consolidative radiotherapy, a Cox model with time-dependant covariates, and a 6-month landmark analyses were performed to examine OS and PFS. Results: A total of 91 patients with at least stable disease following chemotherapy and with no more than 5 residual metastases were analyzed: 51 in the RT group and 40 in the OBS group. Metachronous metastatic disease (following definitive treatment of localized UBC) was more frequent in the OBS group (19% vs 5%, p = 0.02); the median number of metastases in the RT group vs in the OBS group was: 2 (1-9) vs 3 (1-5) (p = 0.04) at metastatic presentation, and 1 (0-5) vs 2 (0-5) (p = 0.18) after completion of chemotherapy (residual lesions), respectively. Two grade 3 toxicities (3.9%) and no grade 4 toxicity were reported in the RT group. With a median follow up of 85.9 months (95% IC [36.7; 101.6]), median OS and PFS were 21.7 months (95% IC [17.1; 29.7]) and 11.1 months (95% IC [9.9; 14.1]) for the whole cohort, respectively. In multivariable analysis: consolidative RT in comparison with observation was associated with improved OS in both the standard analysis (HR = 0.47, p = 0.015) and in the 6-month landmark analysis (HR = 0.48, p = 0.026); and with improved PFS only in the standard analysis (HR = 0.49, p = 0.007). Conclusions: Consolidative radiotherapy for mUBC patients who have not progressed after chemotherapy and with limited residual disease seems to confer both OS and PFS advantage. Prospective data in that field with addition of avelumab are needed.