Cancer-associated myositis in Chinese patients with idiopathic inflammatory myopathies: Malignancy spectrum, risk factors, and validation of the IMACS guideline
Authors' conclusion
The IMACS guideline effectively identifies patients at increased malignancy risk, and a simple refinement score may further improve risk stratification.
Study context
- Population
- Adults with idiopathic inflammatory myopathies (IIM), five tertiary referral centres in China, January 2010 to December 2024eligible patients with IIM
- Participants
- 1,980 adults
- Exposure
- Cancer-associated myositis (CAM) vs non-CAM; IMACS guideline vs IMACS plus refinement score
- CAMn = 176
- Outcome
- CAM prevalence and malignancy spectrum; applicability of the IMACS cancer screening guideline
Methodological detailsmulticentre, five tertiary referral centres
- Multicentre
- Five tertiary referral centres
Main finding
As reported in the abstract
CAM prevalence
CAM
8.9%
176
- Lung cancer (most common malignancy)
- 18.2%
- Breast cancer
- 14.8%
- Thyroid cancer
- 11.9%
- Cancers within 1 year before or after IIM onset
- 76.1%
Observational data: associations, not effects.
Further findings
| Outcome | Refinement score | IMACS alone | P value |
|---|---|---|---|
| Discrimination: refinement score (anti-SAE, elevated CRP, elevated CA125, absence of ILD) plus IMACS vs IMACS alone | P < 0.001 | ||
| AUC | 0.762 | 0.699 |
IMACS risk classification
- CAM patients classified as high-risk
- 65.9%
- Non-CAM patients assigned to moderate-risk category
- 65.4%
Independent factors associated with malignancy (multivariable analysis)
- Risk factors: anti-TIF1γ positivity, anti-SAE positivity, elevated CRP, elevated CA125
- ILD inversely associated with malignancy
Original publication
Cancer-associated myositis in Chinese patients with idiopathic inflammatory myopathies: Malignancy spectrum, risk factors, and validation of the IMACS guideline. Semin Arthritis Rheum. Published 7 August 2026. doi:10.
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