Patient-reported Outcomes for Multicentric Castleman's Disease in a Randomized, Placebo-controlled Study of Siltuximab.

Background: Multicentric Castleman's disease (MCD) is a rare lymphoproliferative disorder driven by dysregulated interleukin-6 production. MCD has a poor prognosis, and treatment is generally noncurative and aimed at symptom relief. Siltuximab is a novel, monoclonal interleukin-6 antibody recently shown to be effective in a registration clinical trial. MCD symptoms, such as fatigue, pain, and weakness, are most appropriately quantified using patient-reported outcome (PRO) measures. We assessed the effect of siltuximab on patient perception of symptoms, functional status, and wellbeing using PRO instruments.

Methods: We analyzed results of a randomized, double-blind trial comparing siltuximab 11 mg/kg every 3 weeks with placebo to treat MCD. Subjects (N = 79) completed the recently developed MCD-Symptom Scale (MCD-SS), the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) scale, and the Short Form (SF)-36 at predetermined time points throughout the treatment period. Scores were compared at baseline and over time between the treatment arms and PRO instruments.

Results: At baseline, the mean number of symptoms reported was 9.2 (standard deviation 3.76) out of 16 total, as measured by the MCD-SS. Fatigue was a key symptom across all PRO instruments. Siltuximab-treated subjects reported early improvements in symptoms compared with subjects in the placebo arm on both the MCD-SS and FACIT-Fatigue scale. Statistically significant improvements in five SF-36 domains were observed in siltuximab-treated patients, namely role physical, role emotional, vitality, bodily pain, and mental health.

Conclusions: Patients with MCD commonly report impairments in functioning, wellbeing, and fatigue at baseline. Siltuximab-treated patients reported significant improvements in these outcomes after treatment.