Reacción a "Some treatments approved for multiple sclerosis are not effective for certain forms of the disease, according to a study. "

It is certainly an interesting study, but it should be interpreted with caution. It is a retrospective study, and like all such studies there are certain methodological issues that limit its findings and conclusions.

Of the total number of patients treated with anti-CD20 therapies in the French multicentre cohort, more than half could not be included for analysis and the authors do not provide data to know whether the included group is truly representative of the patients indicated for these therapies and something similar happens with the control group. It is also important to note that very few patients were included with ocrelizumab (which is the currently approved drug for the management of patients with primary progressive multiple sclerosis - PPMS) and that, due to the indications for which this treatment can be prescribed, the characteristics of the patients included in the two groups (treated and untreated) are very different. As much as the authors used different statistical techniques to control for these differences, the underlying biological changes can often not be adjusted for and ensure a correct comparison.
As expected, many of the untreated patients were included before 2018, when ocrelizumab was approved for patients with PPMS, and therefore, in many of these cases there was no information on MRI scans, a key tool for monitoring and stratifying patients with multiple sclerosis (MS).

Furthermore, it is not specified which treatment regimen they underwent. In the case of ocrelizumab (131 patients) it is marked in the data sheet, but the dose and frequency of administration of rituximab (the largest group in this study with 295 patients) is not clear and is very centre-dependent, so the results reported in any case would refer to these specific doses. There are data suggesting that the impact of anti-CD20 therapies on disability may be related to the dose received, so this would be essential to know.

We are used to seeing published studies of effectiveness in clinical practice in cohorts of patients with relapsing-remitting MS, where the measures of response are somewhat clearer. This is one of the few papers that assesses this effectiveness in patients with progressive forms of MS, but the response measure in this case (the EDSS disability scale) is a measure that is more difficult to interpret, especially when it is collected retrospectively without the rigour required in clinical trials. Of course, these are interesting results, but I don't think they will lead us to change our usual clinical practice.