Background Whether the risk of hospitalized infection is associated with autoimmune diseases in incident cancer patients is unknown.

Objectives To examine the risk of hospitalized infection in incident cancer patients with autoimmune diseases compared with those without autoimmune diseases.

Methods During 2000–2016, we identified 37,027 incident cancer patients from the Cancer Registry database of Taichung Veterans General Hospital. Autoimmune diseases included rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), ankylosing spondylitis (AS), psoriasis (PSO)/psoriatic arthritis (PSA), antiphospholipid syndrome, polymyositis, dermatomyositis, systemic sclerosis, Sjögren's syndrome, mixed connective tissue disease, multiple sclerosis, neuromyelitis optica, palindromic rheumatism, myasthenia gravis, Hashimoto's thyroiditis, immune thrombocytopenic purpura, autoimmune hemolytic anemia, juvenile idiopathic arthritis, adult onset Still's disease, Crohn's disease, ulcerative colitis, Wegner's granulomatosis, and uveitis. Of all subjects, 1,334 had autoimmune diseases. The association between autoimmune diaseases and hospitalized infection risk was shown by calculating hazard ratios (HRs) with 95% confidence intervals (CIs) using cox proportional regression analyses after adjusting for baseline age, sex, cancer stage, hemoglobulin (Hgb), creatinine (CR), log(ALT), log(WBC), and use of biologic agents or tofacitinib.

Results Among all cancer subjects, the mean ± SD age was 60.2±14.7 years, and the proportion of male gender was 55.7%. Of the 1,334 patients with autoimmune diseases, 338 (25.3%) patients had RA, 221 (16.6%) patients had SLE, 61 (4.6%) patients had AS, 151 (11.4%) patients had PSO/PSA, and 563 (46.8%) had other autoimmune diseases. The incidence rates of hospitalized infection were 143.8 per 10³ years in patients with autoimmune diseases and 118.9 per 10³ years in patients without autoimmune diseases. The risk of hospitalized infection was higher in patients with RA and SLE, but not in patients with AS, PSO/PSA, or other autoimmune diseases. Prior use of biologic agents or tofaitinib did not increase hospitalized infection risk. Other risk factors for hospitalized infection included elder age (HR, 1.01; 95% CI, 1.01–1.1), higher cancer stage, CR (HR, 1.04; 95% CI, 1.02–1.06), log(WBC) (HR, 1.21; 95% CI, 1.14–1.28). Female gender (HR, 0.65; 95% CI, 0.62–0.68) and Hgb (HR, 0.89; 95% CI, 0.88–0.90) were associated lower hospitalized infection risk.

Conclusions Hospitalized infection was associated with a comorbidity of RA or SLE in incident cancer patients.

Acknowledgements With thanks to Cancer Registry database and Clinical Informatics Research & Development Center of Taichung Veterans General Hospital for the Support of Clinical data.

Disclosure of Interest None declared