Abstract 778P
Background
Antibiotic (Abx) can affect response to immune-checkpoint inhibitors (ICIs) in patients (pts) with solid tumours. There is limited data on the effects of Abx use on response rates in pts with metastatic urothelial carcinoma (mUC). We studied the effect of Abx use on outcomes in pts treated with ICIs for mUC.
Methods
We conducted a retrospective review of adult pts receiving ICIs for mUC at Cleveland Clinic between 2015 and 2020. Pts included in the study received >/= 2 cycles of ICI therapy with atezolizumab, pembrolizumab, or nivolumab. Abx use was measured in the 60 days preceding or following start of ICI therapy. Statistical analysis included study of PFS and OS, both measured in weeks (wks), through use of Kaplan-Meier method, log-rank testing, and cox-proportional hazard model to calculate hazard ratios (HRs) and 95% confidence intervals.
Results
A total of 130 pts with mUC receiving ICI therapy were included. The Abx-treated group consisted of 84 pts (65%) and the Abx-untreated group consisted of 46 pts (35%). The most commonly used Abx in the Abx-treated groups were fluoroquinolones (34%), cephalosporins (27%), penicillins/carbapenems (18%), and TMP-SMX (14%). The most common indications for Abx use in the Abx-treated groups were empiric treatment (48.6%), pathogen-directed (32.1%), and prophylactic (19.3%). 70 pts received Abx 60-days prior to ICI initiation and 44 pts had Abx 60-days after ICI initiation. Results of log-rank testing showed no statistically significant difference in OS (p = 0.6) or PFS (p = 0.8) between the Abx-treated (median OS 51 wks, median PFS 21 wks) and Abx-untreated (median OS 61 wks, median PFS 18 wks) groups. Abx use 60-days after ICI initiation (median OS 51 wks, median PFS 18 wks) did not significantly decrease PFS (HR=1.3, 95% CI = 0.77-2.2) or OS (HR 1.62, 95% CI 0.9-2.92). Similarly, Abx use 60-days prior to ICI start (median OS 51 wks, median PFS 21 wks) did not significantly decrease PFS (HR 0.91, 95% CI 0.462-1.79) or OS (HR 1.46, 95% CI 0.65-3.28).
Conclusions
In our single institution study, Abx use within 60 days before or after start of ICI did not significantly impact OS and PFS in pts with mUC receiving ICI therapy.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Cleveland Clinic Taussig Cancer Center.
Funding
Has not received any funding.
Disclosure
S. Gupta: Honoraria (self): Merck; Honoraria (self): Exelixis; Honoraria (self): Janssem; Honoraria (self): BMS; Honoraria (self): Seattle Genetics; Honoraria (self): AstraZeneca; Advisory/Consultancy: AstraZeneca; Advisory/Consultancy: BMS; Advisory/Consultancy: Seattle Genetics; Speaker Bureau/Expert testimony: BMS; Speaker Bureau/Expert testimony: Exelixis; Speaker Bureau/Expert testimony: Janssen; Research grant/Funding (institution): BMS; Research grant/Funding (institution): Astellas. All other authors have declared no conflicts of interest.