Internal Psychometric Validation of an International Burden of Illness Survey for Idiopathic Multicentric Castleman Disease.

INTRODUCTION: Idiopathic multicentric Castleman disease (iMCD) is a rare, chronic, debilitating lymphoproliferative disorder where the mainstay of treatment is symptom management. Our recent international patient survey showed that patients with iMCD have a high symptom burden that has a significant negative patient-reported impact on several aspects of daily life. As part of our ongoing work towards the development of an iMCD symptom burden scale, assessing the survey's psychometric properties is a critical step in understanding its adequacy, relevance, and usefulness. As iMCD is a rare disease, there are challenges to conducting such psychometric analyses which we describe. METHODS: As part of the exploratory psychometric analysis, three a priori hypothesis sets (HS) were generated by interviewing an iMCD-experienced clinician, a patient, and a caregiver to explore the iMCD patient survey's internal construct validity, given no gold standard iMCD measure exists for external construct validation. HS-1 hypothesized that a convergent or discriminant relationship exists with the patients' self-assessment of symptom effect on daily life between two potentially related or unrelated symptoms, respectively. HS-2 hypothesized that having a greater number of symptoms has a positive convergent relationship with the patients' assessment of symptoms' effect on daily life. Finally, HS-3 hypothesized that patients receiving treatment versus no treatment was associated with patients reporting less effect of symptom burden on their daily life. Spearman's rank absolute correlation strength (ACS) was used for HS-1 and HS-2 (convergent relationship, ACS ≥ 0.3 and p value < 0.05; divergent relationship, ACS < 0.3), and Cohen's d to quantify standardized absolute effect sizes (AES) for HS-3 (AES ≥ 0.5 and p value < 0.05). RESULTS: Our analyses partially supported HS-1. None of the three positive convergent relationships were supported. Of the six discriminant relationships, only dizziness with impaired cognitive function and tiredness with dizziness were supported. HS-2 analyses showed there was convergent validity between the number of symptoms and their effect on aspects of daily life. HS-3 analyses did not provide evidence to support the hypothesis. CONCLUSION: These internal psychometric construct analyses provide initial support for the bespoke iMCD patient survey and will guide additional work towards the development of the first iMCD-specific symptom burden scale.

Symptom burden in patients with idiopathic multicentric Castleman disease and its impact on daily life: an international patient and caregiver survey.

Background: Idiopathic Multicentric Castleman Disease (iMCD) is a rare inflammatory lymphoproliferative disorder with heterogenous clinical presentations. The symptomatology in iMCD patients remains poorly understood. The aim of this study was to identify the type, frequency and severity of iMCD-related symptoms and the impact of these on the daily lives of iMCD patients and informal-caregivers. Methods: We conducted two bespoke 45-question online surveys for iMCD patients and informal-caregivers of patients recruited from the US, UK, Australia and Canada between April 14 and November 8, 2021. Descriptive data was collected, and a Likert scale was used to quantify the impact of symptoms on various aspects of daily life. Ordinal logistic regression analysis was used to determine associations between age, gender, employment status and symptom burden with aspects of daily life. Findings: Eligible respondents included 51 iMCD patients and 11 informal-caregivers. Patients reported up to 27 unique symptoms, the mean number of symptoms experienced by a patient was 6.7 (range 0-22 symptoms). Most symptoms had a moderate to severe impact on patients' daily lives, with 'pain/discomfort', 'ability to travel', and 'sexual functioning' being the most impacted. iMCD patient characteristics such as being 40 years or older, female, and either disabled or unemployed was significantly associated with adverse impact on several aspects of daily life. Among caregivers, the aspects of daily life that were disproportionately affected was their own social life and freedom, emotional wellbeing, travel/relocation, and work. Interpretation: iMCD patients have widely varied and unappreciated symptomatology. High symptom burden adversely impacts several aspects of patient daily lives as well as their caregivers. Funding: Funding was provided by EUSA Pharma.

Exploring the feasibility of using the ICER Evidence Rating Matrix for Comparative Clinical Effectiveness in assessing treatment benefit and certainty in the clinical evidence on orphan therapies for paediatric indications.

BACKGROUND: The evaluation of clinical evidence takes account of health benefit (efficacy and safety) and the degree of certainty in the estimate of benefit. In orphan indications practical and ethical challenges in conducting clinical trials, particularly in paediatric patients, often limit the available evidence, rendering structured evaluation challenging. While acknowledging the paucity of evidence, regulators and reimbursement authorities compare the efficacy and safety of alternative treatments for a given indication, often in the context of the benefits of other treatments for similar or different conditions. This study explores the feasibility of using the Institute for Clinical and Economic Review (ICER) Evidence Rating Matrix for Comparative Clinical Effectiveness in structured assessment of both the magnitude of clinical benefit (net health benefit, NHB) and the certainty of the effect estimate in a sample of orphan therapies for paediatric indications. RESULTS: Eleven systemic therapies with European Medicines Agency (EMA) orphan medicinal product designation, licensed for 16 paediatric indications between January 2017 and March 2020 were identified using OrphaNet and EMA databases and were selected for evaluation with the ICER Evidence Rating Matrix: burosumab; cannabidiol; cerliponase alfa; chenodeoxycholic acid (CDCA); dinutuximab beta; glibenclamide; metreleptin; nusinersen; tisagenlecleucel; velmanase alfa; and vestronidase alfa. EMA European Public Assessment Reports, PubMed, EMBASE, the Cochrane Library, Clinical Key, and conference presentations from January 2016 to April 2021 were searched for evidence on efficacy and safety. Two of the identified therapies were graded as "substantial" NHB: dinutuximab beta (neuroblastoma maintenance) and nusinersen (Type I SMA), and one as "comparable" NHB (CDCA). The NHB grade of the remaining therapies fell between "comparable" and "substantial". No therapies were graded as having negative NHB. The certainty of the estimate ranged from "high" (dinutuximab beta in neuroblastoma maintenance) to "low" (CDCA, metreleptin and vestronidase alfa). The certainty of the other therapies was graded between "low" and "high". The ICER Evidence Rating Matrix overall rating "A" (the highest) was given to two therapies, "B+" to 6 therapies, "C+" to five therapies, and "I" (the lowest) to three therapies. The scores varied between rating authors with mean agreement over all indications of 71.9% for NHB, 56.3% for certainty and 68.8% for the overall rating. CONCLUSIONS: Using the ICER Matrix to grade orphan therapies according to their treatment benefit and certainty is feasible. However, the assessment involves subjective judgements based on heterogenous evidence. Tools such as the ICER Matrix might aid decision makers to evaluate treatment benefit and its certainty when comparing therapies across indications.

Cost-Effectiveness Analysis of Siltuximab for Australian Public Investment in the Rare Condition Idiopathic Multicentric Castleman Disease.

OBJECTIVES: This paper presents an Australian model that formed part of the health technology assessment for public investment in siltuximab for the rare condition of idiopathic Multicentric Castleman Disease (iMCD) in Australia. METHODS: Two literature reviews were conducted to identify the appropriate comparator and model structure. Survival gain based on available clinical trial data were modelled using an Excel-based model semi-Markov model including time-varying transition probabilities, an adjustment for trial crossover and long-term data. A 20-year horizon was taken, and an Australian healthcare system perspective was adopted, with both benefits and costs discounted at 5%. The model was informed with an inclusive stakeholder approach that included a review of the model by an independent economist, Australian clinical expert opinion and feedback from the Pharmaceutical Benefits Advisory Committee (PBAC). The price used in the economic evaluation reflects a confidential discounted price, which was agreed to with the PBAC. RESULTS: An incremental cost-effectiveness ratio of A$84,935 per quality-adjusted life-year (QALY) gained was estimated. At a willingness-to-pay threshold of A$100,000 per QALY, siltuximab has a 72.1% probability of being cost-effective compared with placebo and best supportive care. Sensitivity analyses results were most sensitive to the length of interval between administrations (from 3- to 6-weekly) and crossover adjustments. CONCLUSION: Within a collaborative and inclusive stakeholder framework, the model submitted to the Australian PBAC found siltuximab to be cost-effective for the treatment of iMCD.