Patients with adult-onset idiopathic inflammatory myopathy (IIM) are at increased risk of cancers.¹ Recently, the International Myositis Assessment and Clinical Studies Group (IMACS) published recommendations on cancer risk stratification and screening for IIM patients.¹ These include risk stratification using IIM subtypes, and clinical and serological factors associated with high, intermediate and low risks of IIM-associated cancer.¹ Patients with high (≥2 high-risk factors) and moderate (1 high-risk factor or ≥2 intermediate-risk factors) cancer risks are recommended to undergo basic and enhanced cancer screening panels at the time of IIM diagnosis, while those with standard risk are recommended to undergo only basic screening.¹ Moreover, annual screening during the 3 years after IIM onset is recommended for high-risk patients.¹ During the EULAR 2024 Congress, Professor Yan, Ki-Tang Iris from the University of Hong Kong presented the results of a local study using real-world data from a Hong Kong Myositis cohort (MyoHK) which aimed to verify the applicability and reliability of this cancer risk stratification tool.¹

In this longitudinal, observational IIM cohort, demographic and clinical data, as well as Myositis Specific Antibody (MSA) status, were collected from IIM patients across 7 centers in Hong Kong.¹ Data from 2004-2023 were reviewed in this study.¹ Patients must have a rheumatologist diagnosis of IIM or fulfillment of relevant IIM classification criteria, while those with known active cancer at the time of IIM diagnosis or whose MSA status was not available were excluded.¹ In total, 467 patients were included in the analysis, among which 69% were female (n=322), the mean age at diagnosis was 54.3±13.5 years, and the median follow-up duration was 75 months (interquartile range [IQR]: 49-146.5 months).¹ Patients were then stratified as having high (n=208, 44.5%), intermediate (n=233, 49.9%), and standard (n=26, 5.6%) cancer risk at the time of IIM diagnosis according to IMACS guidelines.¹ Occurrence of cancer at or up to 3 years after IIM diagnosis was recorded, while risk factors associated with cancer were identified using logistic regression.¹

In total, 57 patients (12.2%) in this cohort developed cancer within 3 years of IIM diagnosis, among which nasopharyngeal (n=19), lung (n=15), and breast (n=8) carcinomas were the most common cancer types.¹ 19.7% (n=41) of patients in the high-risk group were diagnosed with cancer within 3 years, compared to 6.8% (n=16, p<0.001) in the intermediate-risk group, and 0% (n=0, p=0.009) in the standard risk group.¹ However, the difference between the intermediate and standard risk groups was not significant (p=0.161).¹ Among the 57 cancer cases, 44 cancers were detected at initial screening (31 in high risk and 13 in intermediate risk).¹

Among the cancer risk factors included in the IMACS guidelines, dermatomyositis (p<0.001), anti-transcriptional intermediary factor 1γ (anti-TIF1γ) antibody positivity (p<0.001), and anti-small ubiquitin-like modifier-1 activating enzyme (anti-SAE1) antibody positivity (p=0.024) were significantly more common in IIM patients with cancer.¹ On the other hand, the presence of anti-synthetase syndrome (p=0.023), interstitial lung disease (ILD) (p<0.001), Raynaud’s phenomenon (p=0.034), arthritis (p<0.001), anti-MDA5 (p=0.004) and anti-Jo1 (p=0.005) antibody positivity, and myositis associated antibodies (p=0.038) were significantly less common in patients with cancer.¹ Multivariable analysis revealed that anti-TIF1γ positivity (odds ratio [OR]=6.65; 95% CI: 3.24-13.7) and anti-SAE1 positivity (OR=5.95; 95% CI: 1.57-22.5) were associated with increased cancer risk, while ILD was protective for cancer (OR=0.27; 95% CI: 0.12-0.60).¹

The strengths of this study include the long follow-up durations, exceedingly low drop-out rates (<1%), and the retrieval of data from a centralized medical database from the Hong Kong Hospital Authority.¹ However, due to the retrospective nature of the study, there may be confounders by indications as well as the risk of missing data.¹ Additionally, the majority of participants in the study were ethnically Chinese, hence further studies are needed to validate the generalizability of these findings.¹

In summary, the vast majority of patients (94.4%) in the MyoHK cohort would be classified as having high or intermediate risk for cancer based on the IMACS guidelines and subjected to extensive cancer screening.¹ While almost 1 in 5 patients in the high-risk group developed cancer within 3 years of IIM diagnosis, providing real-world evidence that supports the accuracy of IMACS cancer risk stratification, further prioritization among the intermediate-risk group might improve screening effectiveness, particularly in resource-limited settings.¹