Therapy - immunomodulation - Part IThursday, September 29, 2005, 15:30 - 17:00
Long-term follow-up of multiple sclerosis patients treated with interferon beta-1a (Avonex®)P. Vermersch, M. Denève, N. Waucquier, J. de Seze on behalf of the G-SEP (Groupe septentrional d'études et de recherche sur la SEP)
Background: Long term studies provide informations about the behaviour of drugs in the post-marketing period.
Objectives: to describe the long term follow-up of a large cohort of relapsing remitting multiple sclerosis patients treated with interferon (IFN) b-1a (Avonex).
Methods: We included patients followed for at least 5 years. IFNb-1a (Avonex) was initiated before April 1999 in all cases. The population was stratified in two groups according to baseline EDSS: one group with EDSS <= 3.0 and the other with EDSS > 3.0. We analyzed number and reasons for dropouts from treatment, the relapse rate, the number of confirmed disability progression. Survival curves were estimated using Kaplan-Meier method and factors predicting disability using the Cox proportional hazards ratio.
Results: We had valid data of 400 patients from an initial cohort of 404 patients. At baseline, mean (SD) EDSS was 2.95 (1.4) and the relapse rate was 1.5 (1.2). Mean follow-up was 5.05 years. Two hundreds and one patients (50.4%) were treated at least 4 years, more in the group EDSS <= 3.0 than in the group EDSS > 3.0 (59.6% and 36.9 respectively, p < 0.0001). Main reasons for dropouts were switch to secondary progressive form and disability progression. Dropouts for persistence of relapses and for side-effects were rare. EDSS > 3.0 at baseline was associated with a higher risk of dropout. Relapse rate was 0.84 (0.5)(-46% compared to baseline). Mean increase of the EDSS score was 0.48 compared to baseline. Disability progression was observed in 126 patients (32%) not significantly different between the two groups. Disability progression in patients treated at least 4 years was extremely rare. Previous treatment with immunosuppressive or immunomodulating drugs was associated with a higher risk of dropout (p = 0.01).
Conclusion: Low EDSS score at treatment onset were associated with a longer duration of treatment. Treatment failure was mainly related to disability progression rather than to persistence of a high relapse rate. After 4 years, dropouts and disability progression were rare.