Atezolizumab (Atezo) Therapy For Upper Tract (Ut) Urothelial Carcinoma (Uc): Subgroup Analysis Of The Single-Arm International Saul Study In Pretreated Locally Advanced/Metastatic Urinary Tract Carcinoma

488 Background: UTUC is rarer than bladder UC and typically responds poorly to standard chemotherapy. Analysis of 220 biomarker-evaluable atezo-treated patients (pts) in phase II/III trials suggested worse outcomes in UT vs lower tract UC [Galsky, ESMO 2018]. We explored clinical outcomes in pts with UTUC (renal pelvis or ureter) treated with atezo in the SAUL study. Methods: The single-arm SAUL study (NCT02928406) [Sternberg, Eur Urol 2019] enrolled a broader pt population, including pts with poor clinical characteristics and/or immune-mediated conditions, more representative of real-world practice than typically enrolled in randomized phase III immunotherapy trials. Pts with urinary tract carcinoma received atezo 1200 mg q3w until disease progression/unacceptable toxicity. Baseline characteristics, safety and efficacy were analyzed in subgroups of pts with UTUC (subdivided into renal pelvis or ureter UC) vs bladder UC. Results: Baseline characteristics in the 4 subgroups were generally similar, except for a numerically lower proportion of pts with 0 prior lines of therapy for metastatic disease in the UTUC vs bladder UC subgroup (30% vs 41%). Treatment exposure, safety and efficacy are shown below. Conclusions: These exploratory analyses of SAUL showed very similar efficacy and safety in UT vs bladder UC. This provides reassurance that atezo is active and has an acceptable safety profile in pts with UTUC, who are generally expected to have worse outcomes than bladder UC pts. Clinical trial information: NCT02928406 . [Table: see text]