Validating the use of brain volume cutoffs to identify clinically relevant atrophy in RRMS.

BACKGROUND: Baseline brain volume (BV) is predictive at a group level but is difficult to interpret at the single patient level. OBJECTIVE: To validate BV cutoffs able to identify clinically relevant atrophy in relapsing-remitting multiple sclerosis (RRMS) patients. METHODS: The expected normalized brain volume (NBV) for each patient was calculated using RRMS patients from two phase III clinical trials, applying a linear formula developed on the baseline variable of an independent data set. The difference between these expected NBV values and those actually observed was calculated and used to categorize the patients in the low-NBV, medium-NBV, and high-NBV groups. RESULTS: The 2-year probability of 3-month confirmed disability worsening was significantly associated with the NBV categorization ( p = 0.006), after adjusting for treatment effect. Taking the high-NBV group as a reference, the hazard ratios for the medium-NBV and low-NBV groups were 1.22 (95% confidence interval (CI): 0.85-1.76, p = 0.27) and 1.69 (95% CI: 1.11-2.57, p = 0.01), respectively. CONCLUSION: This study validates the use of BV cutoffs to identify clinically relevant atrophy in RRMS study by showing that the three groups classified according to the baseline NBV adjusted for the other prognostic variables have a significant prognostic impact on the risk of disability progression.

Defining brain volume cutoffs to identify clinically relevant atrophy in RRMS.

OBJECTIVE: To define values of normalized brain volume (NBV) that can be categorized as low, medium, or high, according to baseline characteristics of relapsing-remitting multiple sclerosis (RRMS) patients. METHODS: Expected NBV (eNBV) was calculated for each patient based on age, disease duration, sex, baseline Expanded Disability Status Scale (EDSS), and T2-lesion volume, entering these variables into a multiple regression model run on 2342 RRMS patients (pooled FREEDOMS/FREEDOMS-II population). According to the difference between their observed NBV and their eNBV, patients were classified as having low NBV, medium NBV, or high NBV. We evaluated whether these NBV categories were clinically meaningful by assessing correlation with disability worsening. RESULTS: The distribution of differences between observed NBV and eNBV was used to categorize patients as having low NBV, medium NBV or high NBV. Taking the high-NBV group as reference, the hazard ratios (HRs) for 2-year disability worsening, adjusted for treatment effect, were 1.23 (95% confidence interval (CI): 0.92-1.63, p = 0.16) for the medium NBV and 1.75 (95% CI: 1.26-2.44, p = 0.001) for the low NBV. The predictive value of NBV groups was preserved over 4 years. Treatment effect appeared more evident in low-NBV patients (HR = 0.58) than in medium-NBV (HR = 0.72) and in high-NBV (HR = 0.80) patients; however, the difference was not significant ( p = 0.57). CONCLUSION: RRMS patients can be categorized into disability risk groups based on individual eNBV values according to baseline demographics and clinical characteristics.