Risk of cancer in multiple sclerosis (MS): A systematic review and meta-analysis

Objective: To assess the pooled risk of cancer in patients with multiple sclerosis. Methods: We searched PubMed, Scopus, EMBASE, Web of Science, Ovid, google scholar and gray literature (references of studies, conference abstracts) which were published up to September 2019. The search strategy included the MeSH and text words as ((cancer) OR tumor) OR neoplasm) OR "malignant neoplasm) OR "benign neoplasm) AND (Multiple Sclerosis OR Sclerosis, Multiple) OR Sclerosis, Disseminated) OR Disseminated Sclerosis) OR MS (Multiple Sclerosis)) OR Multiple Sclerosis, Acute Fulminating). Results: The first literature search revealed 18,996 articles. After deletion of duplicate articles, finally, 264 articles remained. Excluding non-relevant articles, resulted in including 5 articles which met inclusion criteria. The RR estimated between 0.7 and 1.67 in included articles. The pooled RR estimated as 0.83 (95% CI:0.73-0.96) (I-2 = 90%, P < 0.001). Two studies provided prevalence of different cancers. The pooled prevalence of breast cancer in two studies was 2% (95%CI:2%-2%) (I-2 = 0%). The pooled prevalence of digestive system cancer in two studies was 2% (95%CI:1%-2%) (I-2 = 0%). The pooled prevalence of skin cancer in two studies was 1% (95%CI:0%-1%) (I-2 = 0). Conclusion: The result of this systematic review showed that the risk of cancer in patients with MS is less than the general population.