Patient experience with immuno-oncology-induced cytokine release syndrome: Developing a conceptual model of symptoms and their impacts on patients' lives.

2654 Background: Immuno-oncology (IO) therapy can cause cytokine release syndrome (CRS) events, which are a constellation of co-occurring signs and symptoms that usually present within 24–48 hours after treatment. There is no clinical consensus on the specific sign and symptom profile for IO-induced CRS. The objectives of this study were to better understand the experiences of patients with IO-induced CRS and to use data analysis, clinician insights, and patient interviews to develop a conceptual model to capture CRS symptoms and impacts on patients’ lives. Methods: A targeted literature review was conducted to identify CRS signs and symptoms across IO therapies. Clinician interviews (n=4) further defined clinical signs and symptoms and explored the impacts of CRS events on patients’ lives. An advisory boardof five academic oncologists then commented on this list of clinical signs, symptoms, and impacts. Finally, qualitative concept-elicitation interviews were conducted with US patients (ongoing at abstract submission; expected N=20 by March 2024)to confirm and describe symptom severity and impacts. The final intended patient interview sample will specifically examine symptoms and impacts across subgroups with different CRS severity levels. Results: A total of 35 signs and symptoms were initially identified from the literature review. These were assessed, confirmed, and sorted via clinician interviews, resulting in a refined list of 16 clinical signs and 28 symptoms relevant to IO-induced CRS. Based on inputs from the subsequent clinical advisory board, clinical signs indicative of CRS (such as, hypotension, fever and hypoxia) were confirmed, and a list of symptoms (such as chills, fatigue, nausea and diarrhea) recommended for inclusion in a new instrument suited to capture patient-reported experiences was generated. CRS impacts were also broadly described, emphasizing activities and behaviors affected by reduced energy and motivation levels, symptom-related distress, and the emotional burden of the experience. Ongoing patient interviews will confirm the importance of these identified CRS symptoms and provide more specific descriptions of the impacts of IO-induced CRS events on peoples’ lives. Conclusions: Key symptoms affecting patients’ daily activities included, but were not limited to, chills, fatigue, nausea, and diarrhea. These were used to develop a CRS-specific, patient-centered conceptual model that will be refined upon completion of ongoing patient interviews (full results to be presented at ASCO 2024). This research will serve as a framework to build a patient-reported outcome instrument that accurately captures patients’ experiences with CRS and is sensitive to various CRS severity levels. The proposed instrument may aid in evaluating outcomes in clinical trials and support benefit-risk and tolerability assessments.