Incidence of cancer among female patients with systemic lupus erythematosus in Korea

Abstract

This study aims to ascertain the incidence of cancer in patients with systemic lupus erythematosus (SLE) in comparison with that in the general population in Korea, and to identify the cancer-types, the organ involvement, and the association with immunosuppressive therapy. The study subjects were consecutive SLE patients evaluated at Kangnam St. Mary's hospital between 1997 and 2007. The incidence rate of cancer was calculated and was analyzed in comparison to that of age- and sex-matched cohort obtained from the Korea National Cancer Registry. Nine hundred fourteen patients were observed for a total of 5,716 person-years. A total of 16 cases of cancer occurred. The average age at the diagnosis of cancer and the mean disease duration were 43 years and 11 years, respectively. The standardized incidence ratio (SIR) of all cancers was 1.45 (95% CI 0.74-2.16); The SIRs for the three most frequent cancers were 3.42 for cervix cancer (CI 0.00-7.26), 15.37 for non-Hodgkin's lymphoma (NHL; CI 2.90-37.68), and 43.55 for bladder cancer (CI 8.21-106.78). There were significant differences in the hematologic and renal involvement between SLE patients with cancer and without. Cyclophosphamide therapy, especially with cumulative dose more than 6 g (p = 0.017), seemed to contribute to the increased risk of cancer. Long disease duration, damage, and hematologic involvement were associated with increased risk of cancer occurrence. SLE patients are at high risk for NHL and bladder cancer. Active cancer screening is required in SLE patients with long disease duration and damage who are treated with high dose cyclophosphamide.