Patients with multiple sclerosis (MS) treated with fingolimod undergo a modest but rapid increase in macular volume, research shows.
Almost three-quarters of eyes in the fingolimod-treated group had an increase in macular volume compared with just 37% of eyes in MS patients never treated with fingolimod.
"Moreover, only 9% of eyes in fingolimod-treated patients showed a decline in macular volume compared to 42% of eyes in the non-fingolimod group," report senior researcher Ari Green (University of California, San Francisco, USA) and colleagues in Neurology.
But given that macular volume increased within a very short time period - the average follow up in the study was 5 months - and the known association between fingolimod and cystoid macular edema, the researchers suspect that the increase in volume reflects a form of tissue swelling instead of neuroprotection.
Patients with MS treated with fingolimod exhibit less brain volume loss than patients treated with a placebo or once-weekly interferon-ß-1a, but it is not clear if this represents neuroprotection or other processes.
Assessment of the retinal nerve fiber layer and total macular volume are coming into use as potential surrogate markers for progression in MS. In this longitudinal observational study, the researchers compared changes in macular volume using optical coherence tomography (OCT) in 30 patients treated with fingolimod over a 5-month period.
Macular volume increased by an average of 0.025 mm3 in the fingolimod-treated patients compared with no change in among 30 untreated patients with MS.
The fingolimod-treated patients tended to be older, have longer disease duration, and higher disability scores, but a sensitivity analysis that matched the treated patients with an additional group of patients by age and disease duration showed similar results.
In an accompanying editorial, Marc Dinkin (Weill Cornell Medical College, New York, USA) and Friedemann Paul (Charité-Universitätsmedizin Berlin, Germany) note that the increased macular tissue volume may not actually be an effect of the drug; rather it could have arisen from the flare-up or progression that caused over half of the fingolimod patients to start on the drug.
They write: "These are important results that should cause neurologists to reflect on the true significance of [total macular volume] as measured by OCT before we utilize it in the evaluation of our patients with MS."
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