Effect of disease-modifying treatment on spinal cord lesion formation in multiple sclerosis: A retrospective observational study

BACKGROUND: Spinal cord lesions in multiple sclerosis (MS) are an important contributor to disability. Knowledge on the effect of disease-modifying treatment (DMT) on spinal lesion formation in MS is sparse, as cord outcome measures are seldom included in MS treatment trials. We aim to investigate whether intermediate- or high-efficacy DMTs (i/hDMT) can reduce spinal lesion formation, compared with low-efficacy DMTs (lDMT) and/or no treatment.

METHODS: Relapse-onset MS patients with ≥2 spinal MRIs (interval >3 months and <10 years) were retrospectively identified. The i/hDMT-group was defined as patients who were treated with i/hDMTs during ≥90% of spinal MRI follow-up time. Controls received lDMTs and/or no treatment ≥90% of follow-up duration. In a secondary analysis, only patients using lDMT for ≥90% of follow-up were considered controls. Patients were matched using propensity-scores. Cox proportional hazards models were used to estimate the risk of new spinal lesions.

RESULTS: 323 patients had ≥2 spinal cord MRIs. 49 satisfied i/hDMT and 168 control group criteria. 34 i/hDMT patients were matched to 83 controls. Patients in the i/hDMT-group were significantly less likely to develop new cord lesions at follow-up (HR 0.29 [0.12-0.75], p = 0.01). When the i/hDMT-group was matched to only controls using lDMT ≥90% of follow-up time (n = 17 and n = 25, respectively), there was no statistically significant difference (HR 1.01 [0.19-5.24], p = 0.99).

CONCLUSION: Treatment with intermediate- or high-efficacy DMTs reduces the risk of new spinal cord lesions compared with matched patients receiving no treatment and/or lDMTs. No conclusions could be drawn on whether i/hDMTs provide a larger risk reduction compared to only lDMTs (control group receiving lDMTs ≥90% of follow-up time).