Factors contributing to CSF NfL reduction over time in those starting treatment for multiple sclerosis: An observational study

Background
In multiple sclerosis (MS) neurofilament light chain (NfL) is a marker of neuronal damage secondary to inflammation and neurodegeneration. NfL levels drop after commencement of disease-modifying treatment, especially the highly active ones. However, the factors that influence this drop are unknown.
Objective
To examine the patient and treatment-related factors that influence CSF NfL before and after starting treatment.
Methods
Eligible patients across two centres with two CSF NfL measurements, clinical and MRI data were included as part of an observational cohort study.
Results
Data were available in 61 patients, of which 40 were untreated at the first CSF sampling (T1) and treated at the second (T2; mean T1-T2: 19 months). CSF NfL reduction correlated with age (beta = 1.24 95%CI(1.07,1.43); R2 = 0.17; p = 0.005), Expanded Disability Status Scale (EDSS) (beta = 1.12 95%CI(1.00,1.25); R2 = 0.21; p = 0.05) and the type of MS (beta = 0.63 95%CI(0.43, 0.92); R2 = 0.12; p = 0.018; reference=relapsing MS). The treatment effect on a baseline NfL of 702 pg/mL was 451 pg/ml 95%CI(374,509) in a 30-year-old versus 228 pg/ml 95%CI(63,350) in a 60-year-old. There was no association in CSF NfL reduction with BMI, disease duration or sex. In cladribine- and alemtuzumab-treated patients, the CSF NfL T2/T1 ratio did not correlate with lymphocyte depletion rate at 23 weeks.
Conclusions
In this observational study, we found that factors reflecting early disease stage, including a younger age, lower disability and relapsing MS were associated with treatment response in CSF NfL. Other factors were not found to be related, including lymphopaenia in highly-active treatments.