Cancer incidence in multiple sclerosis; A report from nationwide MS registry of Iran, Guilan

Introduction: Multiple sclerosis (MS) is an autoimmune disease-causing CNS demyelination. There may be a correlation between MS and cancer because of the immunological basis of cancer and MS and also the MS treatment’s role. Purpose: The aim of this research was to determine the prevalence of cancer among MS patients in Guilan province. Methods: This cross-sectional study was conducted in 2021 on 611 MS patients registered in nationwide MS registry of Iran (NMSRI), Guilan. Collected data included age, treatment types, duration of drug use, Expanded Disability Status Scale (EDSS), age at diagnosis, presence of cancer, time interval between MS and cancer diagnosis, comorbidities and medications prescribed for immune related disease. Results: 1.0% (n=6) of MS patients had a cancer diagnosis, mainly after MS diagnosis. The uterine cancer (33.3%, n=2), lymphoma (16.67%, n=1), breast cancer (50%, n=4) were identified. Adenoid cystic carcinoma of the salivary gland (n=1) and lung cancer (n=1) were also diagnosed in one patient with uterine cancer. The average age of cancer patients was greater (47.2±12.6 vs. 37.7±9.9, P<0.001), and no significant correlation was found between sex and cancer (P=0.671). There was no significant correlation between the types of MS treatment, duration of taking medication, MS severity, age at MS diagnosis, and cancer (P>0.05). Cancer was more common in those with underlying diseases (P<0.001), but not in patients with autoimmune disease (P>0.05). Conclusion: The cancer is relatively high prevalent among MS patients compared with general population in Guialn province. And its prevalence was only associated with underlying diseases.