POS1275 NASOPHARYNGEAL CARCINOMA AMONG PATIENTS WITH IDIOPATHIC INFLAMMATORY MYOPATHIES – DATA FROM A MULTICENTRE LONGITUDINAL COHORT IN HONG KONG

Abstract

<p><strong>Background:</strong> Nasopharyngeal carcinoma (NPC) is associated with adult--onset Idiopathic inflammatory myopathies (IIMs), especially in East Asian and South-East Asian heritage. The International Myositis Assessment and Clinical Studies Group (IMACS) recently published recommendations on cancer screening in IIM and suggested nasoendoscopy (NE) at the time of diagnosis in patients with adult-onset IIM in geographical regions prevalent of NPC but its reliability is uncertain.</p><p><strong>Objectives:</strong> To determine the prevalence, risk factors and diagnostic modalities in patients with NPC in Hong Kong.</p><p><strong>Methods:</strong> Consecutive patients with a rheumatologist diagnosis of IIM in 7 rheumatology centres in Hong Kong were included in the MyoHK cohort, which was a longitudinal observational cohort. Electronic patient records were reviewed from 2004 to 2023. Demographic data, clinical features, and Myositis specific antibody (MSA) status were recorded. The occurrence of NPC, the diagnostic investigations and mortality were documented. The risk factors of NPC were compared to IIM patients without NPC and with non-NPC cancer.</p><p><strong>Results:</strong> 550 patients were included with median follow-up durations of 79.5 months (IQR: 41.0 – 166.3). The most common IIM subtypes were Dermatomyositis (DM), anti-synthetase syndrome (ASSD) and clinically amyopathic dermatomyositis (CADM), accounted for 30.5%, 24.2% and 17.1% of IIM cases respectively. Cancer was reported in 110 IIM patients (20.0%), in which 25 patients (22.7% of all cancer) had NPC. Out of the 25 NPC cases, 18 occurred within first 3 years of IIM diagnosis while 6 cases were known before IIM onset. 14 NPC cases were detected by cancer screening at IIM diagnosis. Compared to patients without NPC, NPC patients were more likely to be Male (56% vs 27.8%, p<0.001), with skin involvement (100% vs 62.1%, p<0.001), heliotrope rash (76% vs 32.8%, p<0.001), Gottron’s rash (80% vs 39.6%, p<0.001) and dysphagia (44% vs 21.7%, p=0.006). The association with male gender (28.2%, p=0.01), skin rashes (75.3%, p=0.006), heliotrope rash (42.4%, p=0.003), Gottron’s rash (48.2%, p=0.003) and dysphagia (22.4%, p=0.019) were persistent versus IIM patients with non-NPC cancer. Table 1 summarized the risk factors associated with NPC. In multivariate analysis, Male Gender (OR: 3.098, 95%CI 1.074 – 8.939), anti-TIF1g positivity (OR 5.754 95%CI 1.919 – 17.256) and Heliotrope rash (OR 15.382, 95%CI 1.909 – 123.96) were associated with NPC in IIM patients. Compared to IIM patients with non-NPC cancer, Male gender (OR 3.195, 95%CI 1.013 – 10.071) and Heliotrope rash (OR 7.307, 95%CI 1.510 – 35.352) were associated with NPC. Mortality was reported in 52% of NPC patients, compared to 15.6% in IIM patients without NPC (p<0.001) and 32.9% in IIM patients with non-NPC cancer (p=0.083). In the 19 patients diagnosed with NPC after IIM, NE results were available in 15 patients: 7 presented with nasopharyngeal mass, 5 presented with subtle abnormalities including lymphoid lesion, mucosal swelling, or erythema. 3 patients had initial normal NE findings. All 5 patients with subtle NP abnormalities and 2 out of 3 patients with initial normal NE subsequently had NP biopsy and confirmed NPC. 14 patients underwent computed tomography (CT) scan of the neck and abnormal CT findings were identified in 7 patients (50%). Table 2 summarized the diagnostic evaluation in NPC cases. Among the 4 patients with initial negative NPC screening who developed NPC eventually, 3 had persistent active IIM.</p><p><strong>Conclusion:</strong> NPC accounted for 22.7% of all malignancy in IIM patients in the MyoHK cohort. All NPC patients presented with cutaneous involvement, with male gender, heliotrope rash and anti-TIF1g positivity being associated with increased risk of NPC. Low threshold for NP biopsy, serial NE, or additional imaging evaluation other than CT should be considered in patients with risk factors for NPC or persistently active IIM.</p>