P-146: Measuring symptom improvement in idiopathic multicentric Castleman disease: Protocol for a novel outcome measure

Introduction: Diagnostic criteria for idiopathic multicentric Castleman disease (iMCD) were first published in 2017.1 Symptoms are included in these criteria but there is no disease specific symptom scale to aid clinical care. Yet people with this rare lymphoproliferative disorder have a high symptom burden that impacts aspects of daily life, including work/education, social life, travel, mobility, personal relationships, and sexual functioning.2 A novel symptom burden scale for iMCD is timely and important as knowledge of the disease has evolved and a common metric for assessing progression and treatment outcomes would be beneficial. The aim of the study is to develop a patient reported outcome measure (PROM) to quantify symptom burden in iMCD, for use in clinical practice or clinical trials

Methods: A protocol for the development of a novel, standardized, PROM for assessing symptom burden in iMCD was developed and approved by a multi-stakeholder group (including patients, clinicians, industry representatives, and researchers). This international study has been registered with ClinicalTrials.gov - NCT05995834. A four-stage development process is proposed, that includes a patient advisory and wider multi-stakeholder advisory group. Stage one includes the development of draft PROM content from existing literature and expert opinion. Stage two explores the content validity of the draft PROM via online qualitative interviews with people living with iMCD. In stage three, the revised PROM will be administered quantitatively alongside existing scales to evaluate its psychometric performance and inform decisions on the final PROM. The PROM will be finalized based on the qualitative and quantitative evidence generated and in consultation with project advisors. Finally, in stage four, the PROM will be re-administered to observe change in symptom burden over time. This will be complemented with qualitative interviews in a mixed methods design to estimate a minimally clinically important difference for the measure

Results: Ethics approval for the project has been obtained from Australia, Canada, the United Kingdom, and the United States. The first stage of the project, which involved creating the draft content for the PROM, has been completed. Stage 2 had two parts: reviewing the PROM content and conducting 10 patient interviews, both of which have been finished. The project is now in the third stage, where it is expected that 100 patients will be surveyed using the agreed-upon symptoms identified as important during the consultation processes of stages 1 and 2

Conclusions: A new iMCD symptom burden PROM is being developed jointly by patients, academics, clinicians, and industry professionals. The measure is being developed in accordance with FDA regulatory guidelines, with necessary adjustments for rare diseases. The outcome of this research will be a new, validated symptom burden scale, intended for use in both routine clinical evaluation and clinical trials