Potential interaction of radiation therapy, antibiotic, and steroid use in non-small cell lung cancer patients treated with checkpoint inhibitors: A retrospective analysis.

e20724 Background: The activity of Checkpoint inhibitors (CPI) can be predicted by PD-L1 expression. Recent studies showed that other factors can also have an impact including radiation which is beneficial but the use of antibiotics and steroids can have a deleterious effect. We performed a retrospective analysis of stage IV lung cancer patients treated with CPI at our institution and the impact of radiation treatment as well as the use of antibiotics or steroids in their outcome. Methods: We reviewed the data of 121 patients with stage IV non-small cell lung that were treated with CPI from 2015 to 2017 and analyzed the impact of PD-L1 expression, radiation treatment, steroid and antibiotic use on their progression-free survival (PFS) and overall survival (OS). We determined the use of antibiotics and steroids during any time within 30 days of initiation of treatment with CPI. Results: The median age was 66; there were 57 females and 64 males;23 current smokers, 11 non-smokers and 87 previous smokers; 87 adenocarcinomas, 24 squamous cell histology, and 10 others; 38 patients had low PD-L1 ( < 50%), 46 had high PD-L1 (≥50%) and 37 was unknown. The PFS and OS of patients treated with CPI who had radiation (RT) were not different from patients that did not have RT by Gehan-Breslow Wilcoxon test nor there was a difference based on the PD-L1 expression. The use of steroids (S) had a beneficial impact on PFS but it was numerically better but not significant on OS. Antibiotic (AB) use also had a beneficial impact on PFS and OS. Patients that had CPI as first-line therapy had shorter PFS than patients that had CPI as second-line therapy. There was no difference whether RT was used or not in patients that had antibiotics or steroids. Conclusions: Our analysis showed that several factors can potentially impact the PFS and OS of patients treated with CPI. Contrary to the previous report, the use of Ab or S did not affect adversely the PFS and OS. We did not observe a beneficial effect of RT. The sequence of use of CPI could potentially affect the PFS. This data should be taken with caution as it is a retrospective analysis with a small sample number but it reflects the real-life practice of patients treated outside of a clinical trial setting. [Table: see text]