Poster Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2026

Friend or foe? Impact of concomitant medications on survival outcomes in patients receiving immune checkpoint inhibitors   (146019)

Maia Ismail 1 , Madeleine G Washbourne 1 , Midori Nakagai 2 , Kate Ross 2 , Linzy Sneyd 2 , Marissa Ryan 1 3
  1. Pharmacy Department, Princess Alexandra Hospital, Brisbane, QLD, Australia
  2. Pharmacy Department, Royal Brisbane and Women's Hospital, Brisbane, QLD, Australia
  3. School of Pharmacy and Pharmaceutical Sciences, The University of Queensland, Brisbane, QLD, Australia

Aim: Previous studies suggest concomitant medication use may alter immune checkpoint inhibitor (ICI) efficacy through the modulation of host gut microbiome and immunity. This study aimed to evaluate associations between commonly prescribed concomitant medications and overall survival (OS) in patients receiving ICIs. 

Methods: A multisite retrospective cohort study included patients commenced on first line ICIs between 2020 and 2024 for advanced melanoma, squamous cell, Merkel cell, and renal cell cancers. ICIs administered included pembrolizumab, nivolumab, ipilimumab and nivolumab, nivolumab-relatlimab, cemiplimab, or avelumab. Patients on other concurrent systemic anti-cancer therapies such as cytotoxic chemotherapy or tyrosine kinase inhibitors were excluded. Effect of concomitant antibiotics (aerobic and anaerobic organism cover), corticosteroids (prednisolone equivalent of less that 10 mg, or 10 mg or more), metformin, acid suppression therapy (AST), non-steroidal anti-inflammatory drugs (NSAIDs), psychotropics, and laxatives were evaluated for OS using Kaplan–Meier curves. Univariable and multivariable cox hazard regression models were performed, adjusting for age, sex, Eastern Cooperative Oncology Group (ECOG) performance status, cancer type and stage, and lactate dehydrogenase (LDH) covariates. 

Results: A total of 257 patients were included. Concomitant medication use with ICIs showed variable associations with OS. Kaplan-Meier analysis showed that the use of antibiotics, corticosteroids, ASTs, metformin, and laxatives were associated with poorer OS. However, after multivariate adjustment, corticosteroids (prednisolone equivalent dose of 10 mg or more) and ASTs remained independently associated with poorer OS (HR = 2.08, 95% CI 1.00-4.32, p=0.049) and (HR = 2.02, 95% CI 1.22-2.34, p=0.006), respectively. This suggests that these medications may have independent OS relevance when concomitantly prescribed with ICI therapy. 

Conclusion: Corticosteroid as well as AST use were independently associated with poorer OS in patients receiving ICIs. Prospective studies with larger cohorts are required to explore the effect of concomitant medicines on survival outcomes in patients treated with ICIs.