Validation of the Multiple Myeloma Symptom and Impact Questionnaire (MySIm-Q) in patients with multiple myeloma who were enrolled in the CARTITUDE-4 trial

The Multiple Myeloma Symptom and Impact Questionnaire (MySIm-Q) is a validated, disease-specific patient-reported outcome (PRO) instrument that measures symptoms and impacts experienced by patients with multiple myeloma (MM). We describe key measurement properties of the MySIm-Q instrument using CARTITUDE-4 data. The phase 3 CARTITUDE-4 (NCT04181827) trial compares ciltacabtagene autoleucel with standard-of-care regimens in patients with lenalidomide-refractory MM after 1–3 lines of therapy. Following US Food and Drug Administration guidance on the use of PRO measures in clinical trials, the reliability, as well as aspects of construct validity, convergent and discriminant validity of the MySIm-Q symptom and impact scores (2 separate concepts) were assessed. In total, 361 patients completed MySIm-Q assessments. Internal consistency results met the predefined threshold (McDonald’s ꞷ coefficient > 0.7; ꞷ=0.87 for total symptom scores, ꞷ=0.79 for total impact scores), while test-retest reliability was slightly below this threshold (intraclass correlation coefficient [ICC](2,1) > 0.70; ICC = 0.67 and 0.65, respectively). Known-groups validity of total symptom and total impact scores was established through multiple hypotheses. Factor scores estimated from the confirmatory factor analysis model were highly correlated with simple observed scores calculated in symptom and impact scores. Item-level convergent and discriminant validity was supported for all and nearly all items, respectively. Domain convergent and discriminant validity for total scores were largely met. These results demonstrate that the MySIm-Q yields reliable and valid scores based on a number of evidentiary sources, supporting its use as a fit-for-purpose PRO instrument in clinical outcome assessments for patients with MM. CARTITUDE-4: ClinicalTrials.gov ID: NCT04181827. Date of registration: 27 November 2019. URL: https://www.clinicaltrials.gov/study/NCT04181827.