Value of Annual MRI Monitoring in Patients With Multiple Sclerosis Treated With Ocrelizumab: A Number Needed to Scan Analysis.

Abstract (English)

BACKGROUND AND OBJECTIVES: Current guidelines recommend annual MRI scans during treatment with disease-modifying therapies, including ocrelizumab, in patients with multiple sclerosis (MS) to monitor treatment effectiveness and safety. However, the low rate of radiologic disease activity during long-term ocrelizumab treatment suggests that this recommendation should be re-evaluated to reduce burden on ocrelizumab-treated patients and the healthcare system. We aimed to describe the frequency of radiologic follow-up and the occurrence of radiologic disease activity in a cohort of ocrelizumab-treated MS patients to provide insight into the clinical value and efficiency of annual MRI monitoring in routine practice. METHODS: We included ocrelizumab-treated MS patients from the Amsterdam MS Cohort, who had at least 2 brain MRI scans performed during ≥3 months of treatment. MRI scans were performed as part of routine clinical care and clinical MRI reports issued by radiologist were used. Radiologic activity was defined as either ≥1 contrast-enhancing lesions on a MRI scan performed ≥3 months after ocrelizumab initiation or any new/enlarging T2 lesions on a subsequent MRI scan compared with a scan performed at least ≥3 months after ocrelizumab initiation. The number needed to scan (NNS) was calculated as the inverse of the predicted probability of radiologic disease activity as a function of treatment duration in months, estimated using a mixed-effects logistic regression model. RESULTS: A total of 342 patients (mean age at start ocrelizumab 40.3 years (SD 10.8); 65.8% female; 208 relapsing-onset MS and 41 primary progressive MS) were included, contributing 1,639 follow-up MRI scans. Radiologic disease activity was detected in 29 scans in 23 patients (1.8% of scans; 6.7% of patients) over a median treatment duration of 49 months. The NNS increased with treatment duration, especially after 24 months of treatment, reaching 81.3 at month 30 and 152.9 at month 36. DISCUSSION: Routine annual MRI monitoring in patients with asymptomatic ocrelizumab-treated MS never led to treatments changes. The increasing NNS over time, especially after 2 years of treatment, indicates that MRI intervals can be safely extended in patients with stable MS treated with ocrelizumab, potentially doubling the interval from treatment year 2 onward (i.e.,; rebaseline, year 1, year 2, year 4, and year 8, etc.).