Whole brain volume changes in patients with progressive MS treated with cladribine

To compare changes in whole brain volume measured using MRI scans in patients with progressive MS enrolled in a double-blind, placebo-controlled trial assessing the efficacy of two doses of cladribine (0.7 and 2.1 mg/kg) and to assess the correlations between change in whole brain volume and change in other conventional MRI measures.

Measuring brain parenchymal volumes is an objective and reliable surrogate for the destructive pathologic process in MS. The dynamics and the mechanisms of tissue loss in progressive MS are unclear.

Whole brain volumes were measured using postcontrast T1-weighted scans with 3 mm slice thickness from 159 patients with progressive MS (70% secondary progressive and 30% primary progressive) enrolled in a double-blind, placebo-controlled trial of 12-month duration.

Whole brain volumes were similar in the placebo and cladribine-treated patients on the baseline scans. A significant decrease of brain volume over time was observed both in the entire population of patients (p = 0.001) and in the placebo patients in isolation (p = 0.04). No significant treatment effect of either dose of cladribine on brain volume changes over time was found. In the 54 patients who received placebo, the change in brain volume was not significantly correlated with other MRI measures at baseline (enhancing lesion number and volume and T2-hyperintense and T1-hypointense lesion volumes) or at follow-up (cumulative number of enhancing lesions and absolute and percentage changes of enhancing T2- and T1-hypointense lesion volumes).

This study shows in a large cohort of patients that brain parenchymal loss occurs, even over a short period of time, in progressive MS and that cladribine is not able to alter this process significantly. It also suggests that MRI-visible inflammation and new lesion formation has a marginal role in the development of brain atrophy in patients with progressive MS.