774 Antibiotic administration prior to immunotherapy leads to poor overall survival across multiple malignancies

Background The use of immune checkpoint inhibitors (ICI) has increased significantly in the past five years, along with the number of available drugs and regimens. ICIs have dramatically increased survival in cancer patients, however, there has been data to show that they have reduced efficacy in the presence of antibiotics.1 Antibiotic use prior and during ICI therapy was associated with worsening clinical outcomes in patients with renal cell carcinoma,2 melanoma,3 and non-small-cell-lung-cancer.4 Specifically, exposure within 60 days of initiation of ICIs in NSCLC seemed most detrimental, however, some studies have suggested that antibiotics disrupt intestinal microflora for up to six months.5 6 Therefore, we hypothesized that the duration of the antibiotic effect on ICI efficacy may be present for a longer duration. Methods The electronic medical record was queried at the University of Cincinnati Medical Center for the administration of ICIs and antibiotics. Data was collected on the use, type, and duration of antibiotics before ICI use after administration with relevant demographic and clinicopathologic variables including treatment type, cancer type, staging information, and clinical course including subsequent antibiotic use. Univariant (Fischer’s Exact) and multivariant analysis (multiple logistic regression) were conducted and survival analysis was determined according to log-rank testing. Results 217 patients were examined. The median age was 64 (range 22-93), 38% were female, 73% had ECOG 0-1, and 77% were white. Cancer types included melanoma 24%, non-small cell lung cancer (NSCLC) 34%, small cell lung cancer 2%, renal cancer 11%, urothelial cancer 10%, head and neck cancers 11%, and 16% other primaries. 20% remained on ICI at the time of data entry. The most common ICIs were pembrolizumab, nivolumab, followed by ipilimumab-nivolumab, ipilimumab, and durvalumab. 81 patients of 218 received antibiotics within 6 months of receiving checkpoint inhibitors. Of antibiotics administered, the most common classes were cephalosporins (86%), fluoroquinolones (28%), and glycopeptides (23%) with substantial overlap. Overall survival and progression-free survival was improved for those who did not receive antibiotics prior to ICI therapy (median OS 6.5 vs. 2.3 years, HR 0.36, p Conclusions This data adds to the growing body of knowledge that the use of antibiotics prior to ICI treatment leads to inferior overall and progression-free survival. Acknowledgements We would like to thank the Roman Jandarov, UC Cancer Center, the University of Cincinnati Division of Hematology and Oncology, Department of Internal Medicine of the University of Cincinnati, and the University of Cincinnati Medical Center for their continued support. Ethics Approval IRB 2019-0610 References Pinato DJ, Gramenitskaya D, Altmann DM, Boyton RJ, Mullish BH, Marchesi JR, et al. Antibiotic therapy and outcome from immune-checkpoint inhibitors. J Immunother Cancer 2019;7:287. Ueda K, Yonekura S, Ogasawara N, Matsunaga Y, Hoshino R, Kurose H, et al. The impact of antibiotics on prognosis of metastatic renal cell carcinoma in japanese patients treated with immune checkpoint inhibitors. Anticancer Res 2019;39:6265–71. Elkrief A, El Raichani L, Richard C, Messaoudene M, Belkaid W, Malo J, et al. Antibiotics are associated with decreased progression-free survival of advanced melanoma patients treated with immune checkpoint inhibitors. Oncoimmunology 2019;8:e1568812. Ruiz-Patino A, Barron F, Cardona AF, Corrales L, Mas L, Martin C, et al. Antibiotics impair immune checkpoint inhibitor effectiveness in Hispanic patients with non-small cell lung cancer (AB-CLICaP). Thorac Cancer 2020;(9):2552-2560. Pinato DJ, Howlett S, Ottaviani D, Urus H, Patel A, Mineo T, et al. Association of prior antibiotic treatment with survival and response to immune checkpoint inhibitor therapy in patients with cancer. JAMA Oncol 2019;5(12):1774-1778. Panda S, Khader IE, Casellas F, Vivancos JL, Cors MG, Santiago A, et al. Short-term effect of antibiotics on human gut microbiota. PLoS ONE 2014;9.