Association of Cancer and Anti-Synthetase Syndrome: A Retrospective Multicenter Study.

Objectives: We aimed to assess the incidence of cancer-associated myositis among patients with anti-synthetase syndrome, identify factors associated with cancer-associated myositis, and assess its impact on prognosis.

Methods: We conducted a retrospective multicenter study, including adult patients with anti-synthetase syndrome. Factors associated with cancer were assessed using a multivariable logistic regression model. Unsupervised analysis was used to identify a cluster of patients associated with cancer. Cox proportional hazard ratio model was used to assess impact of cancer-associated myositis on mortality.

Results: Among the 122 patients included, 14 (11.4%) met cancer-associated myositis criteria. Standardized incidence ratio was 5.4 (5.14 to 5.65, P < .0001). Patients with cancer-associated myositis were older, more often had a history of cancer, and had lower creatine kinase level and less muscular weakness. They had a significantly worse overall survival compared with those without (log-rank test χ = 16.2, P < .0001). Age and history of cancer were independently associated with cancer-associated myositis. Patients with cancer-associated myositis segregated within a cluster characterized by an older age, a milder muscular involvement, and less Jo-1 antibodies. Finally, cancer-associated myositis was an independent predictor of death.

Conclusion: Cancer-associated myositis is not rare in anti-synthetase syndrome, with higher incidence compared with the general population. Due to its higher mortality, cancer should be carefully screened, especially in older patients with history of cancer.