I began taking Tecfidera 4 months ago, which was approximately 10 weeks after the onset of my first MS symptoms and subsequent diagnosis. I just had a follow up brain and c-spine MRI which showed no new lesions however the active lesion at the time of my diagnosis has grown from 6mm to 9mm. My neurologist is suggesting that I change medications, however I have had minimal side effects with Tecfidera so am hesitant to make a change. Should I take the enlarged size of this lesion as a sign that the Tecfidera is not working or is it more likely that the lesion increased in size during the 10 weeks before I started the Tecfidera?
Your case exemplifies one of the several reasons why I try to obtain a new baseline MRI 3 months after starting a DMT. Even under the best circumstances, there can be a delay between the date you prescribe a DMT and complete a start up form, and the date when it is actually started. Common reasons for this delay include prior authorizations and written appeals, the requirements of which are increasing in frequency. This delay averages 2 to 12 weeks.
It is uncommon for us to change a DMT because of new or enlarging lesions observed on a new baseline MRI 3 to 4 months after starting a DMT. The main exception is an individual with more than 2 new or enlarging lesions with at least one lesion enhancing after the administration of gadolinium. Another exception is an individual with persistent MRI and clinical activity more than 3 months after starting a DMT.
You are correct in suggesting that the enlarged T2 lesion could have materialized in the 10 weeks prior to starting Tecfidera. If the lesion is both enlarged AND enhancing then it probably developed more recently. Even if the enlarged lesion developed more recently, it is probably an insufficient reason to consider changing treatment. It would be a good reason to repeat the MRI in about 6 months to make sure you have remained stable. Repeat the MRI sooner if you should develop new symptoms.
Revere (Rip) Kinkel MD
Director of the Multiple Sclerosis Program
Professor of Clinical Neurosciences
University of California San Diego