Monthly Monitoring of Plasma NfL in Treated Relapsing-remitting Multiple Sclerosis to Detect Persistent Infraclinical Disease Activity

Reference MRI scan is recommended 6 months after treatment onset in patients with multiple sclerosis (MS), and follow-up scans at 12 months later to monitor subclinical activity. When monitoring treatment response in patients treated with disease modifying treatments (DMTs), the measurement of new or enlarging T2/FLAIR hyperintense lesions (NELs) is the preferred MRI method supplemented by contrast-enhancing lesions (CELs) for monitoring treatment response. However, some studies have suggested the deposition of gadolinium-based contrast agents in the basal ganglia and dentate nucleus of patients who underwent serial MRI acquisitions. Although significant clinical consequences of these deposits have not been demonstrated, further studies are required to better understand the potential long-term biological and clinical effects of gadolinium administration. To circumvent this potential risk, several recommendations suggested avoiding unnecessary use of gadolinium for follow-up scans. New sequences are also developed to replace gadolinium injection for the detection of active lesions. Moreover, MRI remains costly and time-consuming. In addition, systematic yearly MRI monitoring is not adapted to detect silent active lesions. This can delay identification of treatment failure and increase the risk of relapses and disability worsening, especially in the context of escalation therapy. Therefore, biological markers could allow more frequent analysis of disease activity and detect treatment failure earlier than classical clinical and MRI monitoring. Their use would greatly help clinicians to switch for high efficacy treatments (HET) and avoid potential relapses. Measurement of a structural axonal protein, neurofilament, in serum or plasma has shown promise as a marker of neuroaxonal injury and a measure of treatment response. In MS, cerebrospinal fluid (CSF) neurofilament-light chain (NfL) is also increased and is positively associated with MRI lesion load and disability s