Canadian study measures persistence to disease-modifying therapies in MS
Background: It has been 20 years since disease-modifying drugs became available for MS. How are they being used?
Interferons were the first disease-modifying therapies (DMTs) approved in Canada in 1995 and continue to represent one of the first line treatments for relapsing-remitting multiple sclerosis (RRMS) to slow the progression of disability, decrease the frequency of MS attacks, and reduce the number and volume of brain lesions. In over 20 years since the approval of interferons, there have been 13 more DMTs approved by Health Canada for RRMS with varying levels of efficacy. One method for measuring the success of a DMT is to evaluate the length of time (persistence) that individuals with MS continued using the same DMT.
A published article in the Patient Preference and Adherence journal by MS Society funded researchers, Dr. Ruth Ann Marrie from the University of Manitoba and Dr. Charity Evans from the University of Saskatchewan, examines the use of first-line DMTs (beta-interferon-1b, beta-interferon-1a, and glatiramer acetate) over time, to identify factors that may contribute to staying with or stopping DMT use.
The Study: Researchers analyzed health administrative data.
Health administrative data from an insurance company in Manitoba provided information on the health services used, such as physician billing and hospitalizations, as well as data on drugs- dispensation dates, quantity dispensed and days supplied for nearly 98% of the population in the province. The research team collated data from 1996 to 2011 from individuals that filed at least three claims for MS and used the first claim as the date of diagnosis until either death, cancellation of health insurance coverage or end of study. The primary goals of the study were to identify the median time to discontinuation of a DMT (defined by a greater than a 90-day gap in taking the DMT), the percentage of people who resumed taking a DMT after a gap, and factors that are associated with discontinuing a DMT.
Results: Stopping therapy was common, so was restarting; three factors were associated with discontinuation.
The researchers collected data from 721 individuals with MS who were followed for a median of 7.8 years. The most common therapy that was initiated was beta-interferon-1b (33.4%) followed by subcutaneous (under the skin) administration of beta-interferon-1a (22.9%), intramuscular (in the muscle) administration of beta-interferon-1a (22.5%), and finally glatiramer acetate (21.2%). The median time to discontinue a therapy was 4.2 years, which was not influenced by the DMT that was prescribed. Of the 721 individuals, 451 (62.6%) discontinued a DMT, however of all the individuals who discontinued a DMT, 259 (57.4%) restarted a new DMT or reinstated their initial DMT. Factors associated with discontinuing a DMT included MS-related hospitalizations, being younger at the time DMT began or experiencing a long lag time between diagnosis and the start of therapy.
Comment: Some limitations to consider.
While this study provides important information on continued use of some first-line DMTs, there are a number of unanswered questions. First, there was no information available on the severity and progression of MS which may be important when evaluating persistence. Many individuals switch to a second-line therapy if the first-line DMT appears to be ineffective. Second, except for discontinuation due to pregnancy, other reasons for discontinuation were not captured by the administrative data. Finally, these findings do not account for comorbidities, that is, other health problems which may be factors contributing to a decision to stop using a DMT.
Findings from this study will build a better understanding of the reasons why people stop using the DMTs and help healthcare practitioners identify those who may be at high risk for stopping.
Melesse D et al. (2017) Persistence to disease-modifying therapies for multiple sclerosis in a Canadian cohort. Patient Prefer Adherence. 11: 1093-1101.