Cancer and multiple sclerosis in the era of disease-modifying treatments.

Prior to the era of disease-modifying therapies (DMT), multiple sclerosis (MS) was linked to reduced rates of cancer. Early use of immunosuppressors (IS) in MS justifies the follow-up of patients to evaluate a possible increase in the incidence of cancer in these patients. We performed a descriptive study of MS patients with a documented oncological event. Among the 22,563 MS patients in the EDMUS databases, patients with a history of cancer were identified, and cancer risk in a multiple sclerosis cohort (CARIMS) was evaluated. Four groups were defined: (A) MS patients without cancer receiving DMT or not, (B) MS patients with cancer but without any history of DMT, (C) MS patients with cancer who received an immunomodulator (IM), and/or (D) MS patients treated with an IS. A total of 9,269 patients (44.1%) had a history of DMT (52% IM; 18% IS; 30% both); 253 patients with MS and cancer were identified, 182 had a history of DMT. The mean duration of DMT was longer for group D (A: 3.6 years vs. D: 4.9 years; P < 0.01). There was no increased risk of cancer among patients treated exclusively with IM. IS treatment (P = 0.043) and the duration of exposure (P < 0.001) significantly increased the risk of cancer, especially skin cancer, as observed in other autoimmune diseases. This result could influence the attitude of the medical profession with respect to the benefit to risk ratio when proposing DMT to MS patients.