Background/Purpose:  Dermatomyositis (DM) and polymyositis (PM) are rare chronic inflammatory disorders of muscle. The morbidity and mortality associated with these conditions remains significant despite treatment, which typically begins with high-dose corticosteroids. Second-line agents are commonly used in clinical practice, however there are no clear evidence-based guidelines directing their use. We systematically assessed the evidence for immunotherapy in DM and PM.

Methods:  Relevant studies were identified through Ovid Medline and PubMed database searches. Bibliographies of relevant studies were scrutinized for other potentially relevant citations, and research registers of ongoing trials and international conference proceedings were examined to identify research in progress or data as yet unpublished. Randomized controlled trials and experimental studies without true randomization (quasi-randomized) including adult patients with definite or probable DM or PM were evaluated. Trials involving patients with possible, early or mild disease were excluded, as were those where diagnostic certainty was unknown or diagnostic criteria had not been specified. Any type of immunotherapy was considered. Improvement in muscle strength was the primary outcome. Secondary outcomes included improvements in patient and physician global scores, physical function and muscle enzymes. Studies not assessing these outcomes were excluded. Using predetermined criteria, the two authors independently selected trials for inclusion and then assessed these for quality.

Results:  1697 citations were retrieved. 13 trials were identified as potentially relevant, 3 were excluded after full text review. 2 further trials were identified after hand-searching reference lists. 12 studies were selected for full analysis, including a total of 522 participants. Differences in trial design and quality, and variable reporting of baseline characteristics and outcomes made direct comparison impossible. Although no one treatment can be recommended on the basis of this review, improved outcomes were demonstrated with a number of agents including methotrexate, azathioprine, ciclosporin and intravenous immunoglobulin. Plasmapheresis and leukapheresis were of no benefit.  Biologics were well tolerated but were not demonstrated to be of benefit.

Study	Intervention	Conclusion
Bunch et al 1980	Pred + AZA vs. Pred + Placebo	No additional benefit with AZA at 3 months
Hollingworth et al 1982	ALG + AZA vs. Pred	NS trend toward benefit with ALG + AZA
Miller et al 1992	PEX vs. Leukapheresis vs. Sham apheresis	PEX/Leukapheresis of no benefit
Dalakas et al 1993	IVIg vs. Placebo	IVIg beneficial in refractory DM
Villalba et al 1998	MTX + AZA + Pred vs. IV MTX + Pred	NS trend toward benefit with MTX + AZA
Vencovsky et al 2000	CsA + Pred vs. MTX + Pred	MTX and CsA equivalent, but MTX better tolerated
Coyle et al 2008	IFX vs. Placebo	IFX is well tolerated, but has limited efficacy
Van de Vlekkert et al 2010	Pred vs. Dex	Dex not superior to Pred, but fewer side effects
The Muscle Study Group 2011	Pred +ETAN vs. Pred + Placebo	No additional benefit with ETAN, but has steroid-sparing effect
Miyasaka et al 2011	IVIg vs. Placebo	IVIg of no benefit in corticosteroid-refractory PM/DM
Choy et al 2011	Pred vs. Pred + MTX vs. Pred + CsA vs. Pred + MTX + CsA	Adding immunosuppressants to corticosteroid therapy offers no additional benefit
Oddis et al 2013	Ritux early vs. Ritux late	No significant difference between groups, but 83% met DOI
ALG, anti-lymphocyte globulin; AZA, azathioprine; CsA, ciclosporin; Dex, dexamethasone; ETAN, etanercept; IFX, infliximab; IV, intravenous; IVIg, intravenous immunoglobulin; MTX, methotrexate; NS, non-significant; PEX, plasma exchange; Pred, prednisolone; Ritux, rituximab.

Conclusion: More high quality randomized controlled trials are needed to establish the role of second-line agents, in particular biologics, in the treatment of DM and PM.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/evidence-for-immunotherapy-in-polymyositis-and-dermatomyositis-a-systematic-review/