Am I taking too much risk trying to stay on Tysabri with positive JCV numbers?

Here is My Question:
I'm an MS patient who's currently being treated with Tysabri. I've been reluctant to switch because I'm prone to side effects and was relived to have finally found a drug that allowed me to have a decent quality of life. I'm JCV positive and have been for some time, so my neurologist wants me to switch to Ocrevus (though we extended my dosing times which lowered my JCV numbers). Here are my questions. Am I taking too much risk trying to stay on Tysabri with positive JCV numbers?~Are there any doctors who would continue to prescribe Tysabri to someone who's been on it for over a decade and is JCV positive? Thank you!

Answer:
​This is a tough question that we have answered many times on this site. The decision really comes down to relative risk and individual choice.
The main risk factors for PML in people on Tysabri for MS include

1. JCV index positive, particularly JCV index > 0.9
2. Prior chemotherapy either for MS or cancer
3. Duration of treatment > 2 years

Other risks may include older age (> 65) and low weight (< 60 kg) but these risk factors are not listed in the physician drug reference reviewed and accepted by the FDA.

The risk factors for continued MS relapses are younger age (< 50) and relapses or MRI activity in the year prior to starting Tysabri.

We have registry data suggesting a markedly reduced risk of PML in MS patients taking Tysabri on extended dose intervals (usually 6-8 weeks between infusions) but these patients were not separated by JCV index status. A study run by the drug maker of Tysabri did show equal effectiveness of every 6-week infusions versus the usual every 4-week infusions as long as participants received every 4-week infusions for at least a year before extending the dosing interval.

We also know that stopping Tysabri is associated with approximately a 30 % risk of relapse, so we always give a single cycle of anti-CD20 infusion (i.e., Ocrevus or rituximab usually) within 8 weeks of stopping Tysabri to prevent relapse. 

Overall, if people have been stable on Tysabri for many years (like you), are JCV Index positive, and are over age 55, we will often recommend a single infusion of Ocrevus or Rituximab after stopping Tysabri to prevent rebound relapses and then monitor them off of all treatment for any return of disease activity. Before giving them the infusion of Ocrevus or Rituximab, we make sure there is no evidence of presymptomatic PML. We only continue the anti-CD20 therapy infusions or injections in the listed circumstance, if people show a return of disease activity following the initial infusion

I hope this helps. Please discuss these thoughts with your MS specialist