Association of response to first-line chemotherapy with the efficacy of atezolizumab in patients with metastatic urothelial carcinoma.
Authors: Tural Deniz , Olmez Omer Fatih , Sümbül Ahmet Taner , Artac Mehmet , Ozhan Nail , Akar Emre , Cakar Burcu , Kostek Osman , Ekenel Meltem , Coskun Hasan Senol , Selcukbiricik Fatih , Keskin Özge , Paksoy Turkoz Fatma , oruc kerem , Bayram Selami , Yilmaz Ugur , Bilgetekin Irem , Yildiz Birol , Sendur Mehmet Ali Nahit , Erman Mustafa 
Published: March 2021

409 Background: In the current study, we evaluated whether the response first-line chemotherapy could impact atezolizumab benefit in terms of response rate and overall survival in patients with metastatic urothelial carcinoma. Methods: In this study, we present the retrospective analysis of 105 patients with urothelial cancer treated with ATZ after progression on first-line chemotherapy. The association between response to first-line chemotherapy and ATZ was assessed using Fisher’s exact test. Overall survival (OS) was estimated by using the Kaplan-Meier method. Univariate analysis was used to identify clinical and laboratory factors that significantly impact OS. Variables were retained for multivariate analysis if they had a statistical relationship with OS (p˂0.1) and then included the final model if p˂0.05. Results: Best response to first-line chemotherapy was complete response (CR), partial response (PR), stable disease (SD) and progressive disease (PD) in 5(4.8%), 38(36.2%), 16(15.2%), 46(43.8%) patients, respectively. Best response to atezolizumab was CR, PR, SD, PD in 9(8.6%), 22(21%), 23(21,9%), 51(48,5%). Forty (74.1%) of patients who benefited from first-line chemotherapy also benefited from atezolizumab, while only 14 (25.9%) of patients with initial PD after first-line chemotherapy subsequently experienced clinical benefit with atezolizumab (Fisher’s exact test, p=0.001). Patients with clinical benefit from first-line chemotherapy had a higher OS. The median OS of atezolizumab were 14.8 and 3.4 months for patients with clinical benefit and progressive disease in response to first-line chemotherapy, respectively (log-rank p=0.001). In univariate analysis, Patients with clinical benefit from first-line chemotherapy, liver metastases, baseline creatinine clearance less (GFR)than 60 ml/min, Eastern Cooperative Oncology Group (ECOG) performance status (1 ≥), and hemoglobin levels below 10 mg/dl were all significantly associated with OS. Three of the adverse prognostic factors according to the Bellmunt criteria were independent factor of short survival: liver metastases (Hazard Ratio [HR]= 0.6; 95% CI 0.174-0.60; p=0.04), ECOG PS≥1 (HR= 0.36; 95% CI 0.2-0.66; p=0.001), and Hemoglobin level below 10 mg/dl (HR= 0.36; 95% CI 0.2-0.66; p <0.001). In addition, Patients with clinical benefit from first-line chemotherapy (HR= 0.39; 95% CI 0.24-0.65; p <0.001) maintained a significant association with OS in multivariate analysis. Conclusions: Our study demonstrated that clinical benefit from first-line chemotherapy was independent prognostic factor on OS in patients' use of atezolizumab as second-line treatment in metastatic bladder cancer. Furthermore, these findings are important for stratification factors for future immunotherapy study design in patients with bladder cancer who have progressed after first-line chemotherapy.