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.