6ER-038 Investigating co-medication-related toxicity in cancer patients treated with immunotherapy: an observational study

<h3>Background and Importance</h3> Immunotherapy has revolutionised cancer treatment over the past decade. Nevertheless, significant side effects and toxicities remain critical concerns. These adverse reactions are often referred to as immune-related adverse events (irAEs),¹ and they continue to pose challenges in the clinical application of this innovative treatment approach. As part of a programme focusing on patients who have received immunotherapy alone or in combination and have experienced toxicity, we have established a multidisciplinary consultation team, including a clinical pharmacist (CP), to identify the root causes of toxicity. <h3>Aim and Objectives</h3> Our aim was to identify and analyse the possible co-medications that may cause or enhance the toxicity of immunotherapy and their potential clinical impacts. <h3>Material and Methods</h3> The co-medications of patients receiving immunotherapy were collected during individual consultations with the clinical pharmacist (CP). Each co-medication was recorded according to the Anatomical Therapeutic Chemical Classification, as well as all complementary and alternative medicine (CAM) practices. Causality was assessed between the introduction of the product (drug or CAM) and the occurrence of toxicity. A two-week clinical follow-up was performed after discontinuing the co-medication responsible for the toxicity to confirm or reject the hypothesis of drug related causality. <h3>Results</h3> Out of 219 patients, 216 used additional medications. For 32 of them (14.8%), we could identify a causality between co-medication and toxicity. The collected data indicate that the majority of auto and co-medications are associated with hepatic toxicity (n=11), potentially worsening oncological treatment-related toxicity to grade 3 or 4, followed by haematological disorders (n=8) and neurological disorders (n=2). The co-medications involved included drugs acting on the gastrointestinal system (n=9), treatments for cardiovascular comorbidities (n=7), serotonin antagonists (n=5), as well as complementary and alternative medicine (CAM) such as curcumin (n=2) and red yeast rice (n=2). <h3>Conclusion and Relevance</h3> We found that most co-medications analysed played an important role in enhancing irAEs, suggesting the promotion of immunotherapy toxicity. The detection of these cases could enable clinicians to monitor the treatment instead of discontinuing treatment altogether, likely to jeopardise the patient vital prognosis. <h3>References and/or Acknowledgements</h3> Wang SJ, Dougan SK, Dougan M. Immune mechanisms of toxicity from checkpoint inhibitors. <i>Trends Cancer</i>. 2023 <h3>Conflict of Interest</h3> No conflict of interest