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Sample sizes for brain atrophy outcomes in trials for secondary progressive multiple sclerosis
D R Altmann1, B Jasperse, F Barkhof
1Medical Statistics Unit, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E7HT, UK. daniel.altmann@lshtm.ac.uk
Neurology
|November 14, 2008
Summary
Sample size calculations for secondary progressive multiple sclerosis (SPMS) trials indicate that SIENA and central cerebral volume (CCV) measures are feasible for assessing brain atrophy reduction.
Area of Science:
- Neurology
- Radiology
- Clinical Trials
Background:
- Progressive brain atrophy in multiple sclerosis (MS) is linked to neuroaxonal and myelin loss.
- MRI measures of brain tissue loss are critical outcome measures in MS treatment trials.
Purpose of the Study:
- To investigate the sample sizes required to demonstrate a reduction in brain atrophy.
- To compare three outcome measures in a parallel-group, placebo-controlled trial for secondary progressive MS (SPMS).
Main Methods:
- Utilized MRI data from 43 SPMS patients in a placebo arm over 3 years.
- Measured central cerebral volumes (CCVs) via semiautomated segmentation and normalized brain volume (NBV) using SIENAX.
- Calculated sample sizes for SIENA, CCV, and SIENAX methods based on estimated parameters.
Main Results:
- For a 2-year trial, minimum sample sizes per arm to detect a 50% treatment effect at 80% power were 32 (SIENA), 69 (CCV), and 273 (SIENAX).
- Two-year sample sizes were significantly smaller than 1-year sizes across all methods (SIENA: 44%, CCV: 55%, SIENAX: 71% reduction).
Conclusions:
- SIENA and CCV are feasible and efficient outcome measures for placebo-controlled SPMS trials.
- These measures can effectively assess treatment effects on brain atrophy.
