Background: Immune checkpoint inhibitors (ICI) have changed treatment paradigm in advanced cancer management. Factors affecting survival in patients managed with ICI are not fully understood. Concomiitant use of antibiotics early in the treatment phase is a factor being investigated. This study aims to compare survival differences in 2 groups of patients treated with ICI for advanced cancers with or without antibiotics use in the first 4 weeks of treatment. CHHHS services 250 000 population in Far North Queensland.
Methods: Retrospective single-site study at a regional centre in Queensland investigating patients receiving ICI without chemotherapy for advanced cancers (melanoma, non-small cell lung cancer, head and neck squamous cell carcinoma, urothelial cancer, renal cell carcinoma, mesothelioma) from 2015 to 2019. Baseline demographics and prognostic factors data including age, ECOG performance score, comorbidities, number of metastatic sites and presence of brain metastasis were collected. Antibiotics use within 4 weeks after ICI commencement was examined. Cox proportional hazard model and Kaplan-Meier analysis was used to examined median progression free survival (PFS) and median overall survival (OS) in 2 cohorts with and without antibotics treatment.
Results: 184 patients were treated with ICI in this study. 39 patients (21%) recevied antibiotics within first 4 week of ICI treatment and 145 patients (79%) did not. Patient who did not receive antibiotics had median PFS of 9.4 months compared with 4.3 months for those who did (HR of 2.018 , P= 0.001). median OS was 38.2 months compared with 10.5 months (HR of 2.351, P=0.001)
Conclusion: This study demonstated statistically significant trend toward shorter survival times in patients with concomittent antibiotics use. Further research with multivariate analysis correcting for covariates such as age, comorbidites, ECOG performance status, number of metastatic sites is in progress and will be presented in future publications.