Efficacy of Rituximab in CANOMAD: A Systematic Review

CANOMAD, characterized by chronic ataxic neuropathy, ophthalmoplegia, immunoglobulin M (IgM) paraprotein, cold agglutinins, and disialosyl antibodies, encompasses a clinical, radiological, and laboratory diagnosis. CANOMAD is a rare condition, with fewer than 100 cases reported in the literature. The understanding and diagnosis of the disease have improved in the last few years, but the treatment of CANOMAD is mainly unknown, and there is not a clear consensus about it. We conducted a systematic review regarding the efficacy of rituximab in CANOMAD's treatment to investigate the clinical and biological response of CANOMAD in patients treated with rituximab. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Meta-Analyses of Observational Studies in Epidemiology (MOOSE) reporting guidelines for this systematic review. To analyze the bias of the study, we used the Joanna Briggs Institute's (JBI) Critical Appraisal Checklist to analyze the bias of the case reports, and we used the Risk of Bias in Non-Randomized Studies of Interventions (ROBINS-I) tool for the observational studies. We only included case reports, case series, and observational studies written in English with patients formally diagnosed with CANOMAD and treated with rituximab. We excluded systematic reviews, literature reviews, and meta-analyses. We investigated the clinical and biological responses of the patients to rituximab. The clinical response was classified as complete recovery (CR), partial response (PR), stable disease (SD), and non-response (NR). We gathered 34 patients. The literature uses a modified Rankin score to define complete improvement (CR), partial response (PR), stable disease (SD), and progression. Clinically, there were three patients with CR, five with PR, 15 with SD, and 11 with progression. The biological response was assessed by measuring the decrease in antibody titers in 27 patients. Among those, six patients had CR, 12 had PR, eight had SD, and one had progression. Among 15 patients with neurological evaluation, 10 had ocular symptoms, and two presented with bulbar symptoms. Seven of the ten patients with ocular symptoms had SD, two had PR, and one had progression. Only 14 patients had a report of demyelinating features. Three had an axonal pattern, six had a demyelinating pattern, and five had a mixed pattern. Among patients with an axonal pattern, three had an SD. Among patients with a demyelinating pattern, three had a PR, two had an SD, and one had progression. Among patients with a mixed pattern, four had SD, and one had progression. We concluded that patients with CR have a shorter disease duration than patients with PR, SD, or progression. In addition, patients with CR had longer follow-ups than the other groups, suggesting that being treated early with rituximab improves the clinical outcome and has a sustained effect. There were no differences in the frequency of ocular and bulbar symptoms among patients with CANOMAD. The axonal pattern is more common in patients with SD, suggesting that axonal and mixed patterns could be markers of a bad prognosis.