The following article features coverage from the Society of Immunotherapy of Cancer (SITC) 2020 meeting. Click here to read more of Cancer Therapy Advisor‘s conference coverage.

Antibiotic use up to 6 months before immune checkpoint inhibitor (ICI) treatment may results in worse outcomes among patients with cancer, according to the results of a retrospective study presented at the virtual Society for Immunotherapy of Cancer 35th Anniversary Annual Meeting & Preconference Programs (SITC 2020).

Previous studies suggest that antibiotic use prior to ICI treatment may reduce efficacy. “We hypothesized that administration of antibiotics up to 6 months before ICI administration may affect survival,” Eric Vick, MD, PhD, of the University of Cincinnati Cancer Center in Ohio, and presenter of the study, said.

The retrospective study evaluated electronic health record data from 216 patients with cancer who were treated with ICIs at the University of Cincinnati Medical Center, Ohio.

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The median patient age at baseline was 64 years, and 38% of patients were female. Cancer types included melanoma, non-small cell lung cancer, renal cell carcinoma, urothelial carcinoma, head and neck cancer, and others. The majority of cancers were stage IV, followed by stage III and stage I to II. Most patients were treated with anti–programmed cell death 1/programmed cell death ligand 1 (PD-1/PD-L1) antibody monotherapy.

Antibiotics were administered to 37.5% of patients prior to ICI treatment, with the most common being of the cephalosporin class (31.4%), followed by the fluoroquinolone class (14%), and the penicillin class (12.8%).

Antibiotic use prior to ICI treatment was significantly associated with shorter progression-free survival, with a median of 0.46 years compared with 1.1 year among patients who did not receive an antibiotic (hazard ratio [HR], 1.7; 95% CI, 1.2-2.5).

Overall survival was also shorter among patients who had received antibiotics, with a median of 2.3 years compared with 6.5 years among patients who had not received antibiotics (HR, 3.4; 95% CI, 2.2-5.3).

Dr Vick concluded that their data demonstrate “that antibiotic administration up to 6 months prior to ICI administration may be associated with an inferior survival outcome.” A subsequent analysis is planned to further characterize this association.

Read more of Cancer Therapy Advisor‘s coverage of the SITC 2020 meeting by visiting the conference page.


Vick EJ, Abuali I, Ludvigsen S, et al. Antibiotic administration prior to immunotherapy leads to poor overall survival across multiple malignancies. Presented at: Society for Immunotherapy of Cancer 35th Anniversary Annual Meeting & Preconference Programs (SITC 2020); November 11-14, 2020. Abstract 774. J Immunother Cancer. 2020;8(Suppl 3):A656–A959.