Today I’ve read an abstract concerning an extra dose of 1000 mg rituximab.
Vitall, E.M. and
colleagues published the following paper: “An extra dose of rituximab improves
clinical response in rheumatoid arthritis patients with initial incomplete B
cell depletion: a randomised controlled trial” (Link: http://ard.bmj.com/content/early/2014/01/17/annrheumdis-2013-204544.abstract).
Conclusion: “In rituximab-treated patients with incomplete B cell depletion
(predictive of poor response), an extra 1000 mg infusion of rituximab at 4 weeks produced both
better depletion and clinical responses than placebo with no worsening of
safety. Degree of depletion is an important, but modifiable, determinant of
response.”
M. Mahevas and colleagues
were interested to investigate the following problem: “Efficacy and safety of
rituximab given at 1,000 mg on days 1 and 15 compared to the standard regimen
to treat adult immune thrombocytopenia” (Link: http://www.ncbi.nlm.nih.gov/pubmed/23798363).
“The efficacy of two (RTX) regimens: standard therapy of 375 mg/m(2) weekly for
4 weeks vs. a rheumatoid arthritis (RA) regimen of 1,000 mg on days 1 and 15,
to treat ITP was compared.” “Tolerance was good and comparable between the two
groups. The RA regimen is an effective and safe alternative to the standard
regimen to treat adults with ITP.”
And I’d like to point out
to a third study, which has been presented at the ACR 2013 Meeting in San Diego
[498] by M. Bredemeier and colleagues: A Systematic Review and Meta-Analysis
Comparing Low- Versus High-Dose Rituximab For Rheumatoid Arthritis.”
Conclusion: “Low-dose RTX has similar effectiveness and met noninferiority
criteria for most primary outcomes. Considering the lower cost, it should be
the standard RTX regimen for rheumatoid arthritis.”
And I nearly forgot this study, presented at the ACR 2013 Meeting in San
Diego [500] by K. Chatzidionysiou and colleagues: “Fixed Versus On-Flare
Retreatment With Rituximab In RA—Results From The Cererra Collaboration.”
Conclusion: „A fixed retreatment strategy with RTX in RA seems to be more effective
than the retreat ‘on-flare’ strategy.”
The studies show that there are still a couple of unresolved problems
both in treating RA and ITP, not to mention other entities. Vitall’s study
tells us to consider an extra dose, so we need to monitor B-cell depletion,
which we usually don’t do in routine treatments. Reimbursement of lab tests
differs in different countries. Here in Germany there might be differences in
which kind of health care provider is included. Maybe there’s also the problem
of an off-label use. But I think we should consider a third dose before
switching to another boDMARD.
Mahévas’ study shows us, that even in ITP a less aggressive strategy
might also work. And this leads to the study of M. Bredemeier and colleagues.
They describe another possible group of patients, who need less rituximab. And
the last quoted study favours a fixed strategy instead of an “on-flare”
strategy, but doesn’t answer, if a strategy shortly before a flare would
succeed. I know the difficulty lies in determinating “shortly before a flare”;
but that’s where we rheumatologists come into play.
To sum it up, in treating RA patients with rituximab we might encounter a
group that needs a higher dose, a group that needs a standard dose, another one that
needs a lower dose, and these groups might be further divided to fixed or variable infusion intervals. No easy task and more studies are needed.
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