OP0083 MALIGNANCY RISK STRATIFICATION AND DETECTION RATE IN A HONG KONG MYOSITIS COHORT USING THE INTERNATIONAL MYOSITIS ASSESSMENT AND CLINICAL STUDIES GROUP GUIDELINE ON CANCER SCREENING
Authors: I. Y. K. Tang, W. L. Li, D. Chan, C. W. S. Chan, V. H. S. Tang, L. T. H. Luk, R. Ho, B. T. L. Lai, M. L. Lee, H. So
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Adult-onset Idiopathic inflammatory myopathies (IIMs) are at risk of malignancy. The International Myositis Assessment and Clinical Studies Group (IMACS) recently published recommendations on cancer risk stratifications and screening in IIM. Patients in the high or intermediate risk group should undergo enhanced cancer screening at diagnosis. However, the applicability and reliability of the recommendations are unknown[1]. <h3>Objectives:</h3> To determine the cancer risk profile and cancer detection rate using the IMACS recommendations on cancer screening in a Hong Kong Myositis (MyoHK) cohort. <h3>Methods:</h3> MyoHK was a longitudinal observational cohort that collected data from patients with rheumatologist diagnosis of IIM from 7 rheumatology centres in Hong Kong. For the purpose of the current study, the data were reviewed from 2004-2023. Patients with known active cancer at the time of IIM diagnosis and patients with uncertain myositis specific antibody (MSA) status were excluded. Demographic data, clinical features and MSA status were recorded. IIM patients were stratified into standard, intermediate or high-risk subgroups at the time of IIM diagnosis according to the IMACS guideline using age &gt;40 years, male sex, IIM subtypes, MSA status, symptoms including dysphagia, necrotic/ulcerative skin lesion, interstitial lung disease (ILD), arthritis or Raynaud's phenomenon. The occurrence of malignancy from the diagnosis of IIM to 3 years after the diagnosis was documented. <h3>Results:</h3> 550 patients were identified from the MyoHK cohort, 24 patients were excluded for active cancer before IIM and 59 patients were excluded for unavailable MSA. 467 patients were included in the analysis with 322 (69%) female and a mean age of IIM diagnosis of 54.3 ± 13.5 years. The median follow-duration was 75 months (IQR 49 – 146.5). The most common clinical subtypes were anti-synthetase syndrome (28.5%), followed by dermatomyositis (27.4%) and clinically amyopathic dermatomyositis (16.9%). 431 patients (92.2%) had at least one high risk factor for cancer. 208 patients (44.5%) were stratified to high cancer risk group, 233 patients (49.9%) were stratified to intermediate cancer risk and 26 (5.6%) were stratified to standard risk group. The distribution of cancer risk factors at diagnosis is shown in Table 1. Cancer within 3 years of IIM diagnosis occurred in 57 patients (12.2%). Nasopharyngeal carcinoma, lung cancer and breast cancer were the top 3 cancer diagnoses, affecting 18, 15 and 8 patients respectively. 19.7% of patients in the high-risk group were diagnosed with cancer, compared to 6.8% and 0% in the intermediate and standard risk group respectively (p&lt;0.001). 44 cancers (31 in high-risk and 13 in intermediate risk) were detected by initial cancer screening at diagnosis. 7 out of 13 cancer patients with initial negative screening had persistent active IIM and were subsequently diagnosed with cancer within 3 years of IIM diagnosis. Among the cancer risk factors included in the recommendation, anti-TIF1g (OR 6.65, 95%CI 3.24-13.68) and anti-SAE1 (OR 5.95, 95%CI 1.57 – 22.51) positivity were associated with increased cancer risk whereas ILD was protective for cancer (OR 0.27, 95%CI 0.12– 0.60) on multivariate analysis. Table 2 summarized the risk factors associated with cancer. <h3>Conclusion:</h3> Vast majority of IIM patients (94.4%) were indicated for enhanced cancer screening at diagnosis. Almost 1 in 5 patients in the high-risk group had cancer, compared to none in the standard risk group. However, further risk stratification among the intermediate risk group, which represented half of the IIM patients, is needed to better determine the cancer probability. <h3>REFERENCES:</h3> [1] Oldroyd AGS, et al. International Guideline for Idiopathic Inflammatory Myopathy-Associated Cancer Screening: an International Myositis Assessment and Clinical Studies Group (IMACS) initiative. Nature Reviews Rheumatology 2023;19(12):8. <h3>Acknowledgements:</h3> MyoHK is supported by the project fund from the Hong Kong Society of Rheumatology. <h3>Disclosure of Interests:</h3> <b>None declared.</b>