Treatment Patterns in Dermatomyositis Patients in the UK: A Cohort Study using Clinical Practice Research Data Link (CPRD)

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Lay Summary

Dermatomyositis (DM) is a rare, chronic disorder of the muscles and skin. It leads to moderate to severe muscle weakness along with inflammation of the muscle; it is also associated with a severe rash that can occur on the hands, face, trunk, knees or elbows. It is commonly diagnosed with blood tests for muscle function, muscle tissue samples, and measurements of electrical activity in the muscle. Current treatments for DM are limited and often aim to manage disease symptoms. Due to the widely varying symptoms between DM patients, typical patterns of treatment are not well understood. For instance, patients may be prescribed steroid medications, immunosuppressants, or other therapies to manage pain or symptom burden. These therapies may occur in differing orders across patients. The primary goal of this study is to chart out the major treatment patterns within DM patients in the UK. This will enable a more detailed understanding of the current therapies in use, together with the therapy journey that patients undertake. This is expected to confer a public health benefit by establishing the typical treatment pathways available to patients. In turn, this may enable greater transparency for both patients and researchers in understanding how DM is managed in primary care settings.

Technical Summary

Dermatomyositis (DM) is a rare, chronic inflammatory myopathy, associated with severe weakness of trunk and limb muscles, together with a heliotrope rash. Existing treatments are palliative and seek to restore activities of daily living. The heterogenous symptoms of DM can lead to diverging treatment pathways across patients; currently, major lines of therapy are not well understood. The aim of this study is to characterise treatment patterns amongst DM patients in the UK. The study population will be primary care patients within the UK, registered with a GP practice on or before January 1st 2009 and with a DM diagnosis recorded during the period January 1st 2010 to December 31st 2022. This is an observational, retrospective cohort study using data collected from primary care, via patient encounters with their GP. Data sources for the study will be CPRD Gold and CPRD Aurum – no data linkage will be performed. Descriptive analyses (specifically, lines of therapy analysis, reporting Ns and percentages of patients falling within each therapy line over time, and visualised with Sankey plots) will be applied to understand the treatment pathways of the study population. No inferential testing or statistical modelling will be performed. The intended public health benefit of the study will be to help better establish the typical clinical treatment journeys for DM patients; this may be of benefit in the development of future therapy lines, to assist with situating new therapies in clinical treatment regimen.

Health Outcomes to be Measured

1) Characteristics of defined DM patients, specifically body mass (Kg);
2) Medical therapies: (i) Time to initiation of a specific DM treatment will be defined as the time interval between the date of index DM diagnosis and start date of the treatment of interest; (ii) Time to treatment switch will be defined as the time interval from initiation of treatment of interest to treatment switch (first treatment had to be discontinued for the switch to appear); (iii) Time to add-on will be defined as the time interval from the initiation of treatment of interest to the treatment add-on (treatment initiated >30 days from the start of the first treatment and overlapped with another treatment); (iv) Time to treatment discontinuation will be defined as the time interval from treatment initiation to discontinuation.


Kristin Moy - Chief Investigator - Alexion Pharmaceuticals, Inc ( USA )
Daniel Carey - Corresponding Applicant - Alexion Pharma International Operations Limited (Ireland)
Tony Chuang Liu - Collaborator - Alexion Pharma GmbH ( Switzerland )