Over three decades study populations in progressive multiple sclerosis have become older and more disabled, but have lower on-trial progression rates: A systematic review and meta-analysis of 43 randomised placebo-controlled trials

BACKGROUND

Progression is the major driver of disability and cost in multiple sclerosis (MS). However, the search for treatments in progressive multiple sclerosis (PMS) has not mirrored the success in relapsing MS.

OBJECTIVES

To assess changes in PMS trials over time.

METHODS

PubMed, MEDLINE and Embase were searched to identify randomised, double-blind, placebo-controlled trials in PMS. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used, study quality was assessed and trends were examined by regression.

RESULTS

Placebo groups of 43 studies published between 1988 and 2018 were included. The mean age at trial entry increased by 9.8 years per decade (95% confidence interval (CI): [2.7; 4.9]; p < 0.001). Mean baseline Expanded Disability Status Scale (EDSS) scores increased by 0.36 points (95% CI: [0.09; 0.62]; p = 0.009) and disease durations at baseline were prolonged by 1.8 years (95% CI: [0.7; 2.9]; p = 0.003) per decade. The trials became larger, specifically placebo groups increased by about 222 patients (95% CI: [36; 409]; p = 0.021) and 88 patients (95% CI: [12; 165]; p = 0.025) per decade for primary progressive multiple sclerosis (PPMS) and secondary progressive multiple sclerosis (SPMS), respectively. The proportion of patients on placebo experiencing disability progression within 24 months decreased by 7.6 percentage points (95% CI: [1.2; 14.1]; p = 0.022) per year.

CONCLUSION

Over three decades, PMS trial populations changed and are now older, with a longer disease duration and more disability, with lower on-trial progression rates.

Explaining temporal trends in annualised relapse rates in placebo groups of randomised controlled trials in relapsing multiple sclerosis: systematic review and meta-regression

BACKGROUND

Recent studies have shown a decrease in annualised relapse rates (ARRs) in placebo groups of randomised controlled trials (RCTs) in relapsing multiple sclerosis (RMS).

METHODS

We conducted a systematic literature search of RCTs in RMS. Data on eligibility criteria and baseline characteristics were extracted and tested for significant trends over time. A meta-regression was conducted to estimate their contribution to the decrease of trial ARRs over time.

RESULTS

We identified 56 studies. Patient age at baseline (p < 0.001), mean duration of multiple sclerosis (MS) at baseline (p = 0.048), size of treatment groups (p = 0.003), Oxford Quality Scale scores (p = 0.021), and the number of eligibility criteria (p<0.001) increased significantly, whereas pre-trial ARR (p = 0.001), the time span over which pre-trial ARR was calculated (p < 0.001), and the duration of placebo-controlled follow-up (p = 0.006) decreased significantly over time. In meta-regression of trial placebo ARR, the temporal trend was found to be insignificant, with major factors explaining the variation: pre-trial ARR, the number of years used to calculate pre-trial ARR and study duration.

CONCLUSION

The observed decline in trial ARRs may result from decreasing pre-trial ARRs and a shorter time period over which pre-trial ARRs were calculated. Increasing patient age and duration of illness may also contribute.