Many decisions to stop taking the multiple sclerosis treatment Tysabri (natalizumab) appear to be based largely on subjective factors such as patients’ or physicians’ view of the risk, rather than objective assessments of the risk, a study indicates.
Tysabri is an approved immunotherapy for active relapsing-remitting multiple sclerosis (RRMS). Despite its benefits, there is risk a patient will develop a severe viral infection of the central nervous system called progressive multifocal leukoencephalopathy (PML).
Only 664, or .4 of 1 percent, of 152,500 RRMS patients taking Tysabri through June 2016 developed PML, Tysabri said. Some patients refuse to use it, or stop taking it, because of the risk, however.
The study, “Is the risk of progressive multifocal leukoencephalopathy the real reason for natalizumab discontinuation in patients with multiple sclerosis?,” was published in the journal Plos One.
Researchers asked 699 patients and 99 physicians whether objective measures of PML’s risk, such as the low percentage of patients developing PML, figured into their treatment decisions.
Only 13 percent of the Tysabri-treated MS patients discontinued therapy, the team learned.
Neither the duration of the treatment nor the amount of virus in a person’s system was associated with their decision, the team found. This suggested that PML biomarkers were not the reason some patients decided to stop Tysabri.
The biomarkers some scientists encourage doctors to use to assess the risk of a patient developing PML are duration of Tysabri treatment, prior use of immunosuppressants, and previous exposure to a virus.
They are not enough to predict with accuracy the risk of a patient developing PML, the researchers said. They believe additional immunological markers or genetic screenings will lead to better predictions of PML risk patients.
“The introduction of three-stage risk stratification algorithms has not led to a reduction of PML incidence in NTZ [natalizumab]-treated patients. This suggests that factors other than objective PML risk play an important role in the highly complex decision-making process concerning therapy initiation and continuation,” the researchers wrote.
Patients’ perception of their risk of developing PML with Tysabri and their physician’s judgment appear to be the main factors in decisions to discontinue the treatment, the researchers said. Objective factors that were likely disregarded in the decisions included a low incidence of PML in MS patients, good patient response to the treatment, and low rates of adverse side effects, the team said.
“Physicians should be aware of the different weighting of subjective and objective factors in their advice to achieve the best-possible risk-benefit ratio for the individual patient,” the researchers wrote.