Cancer Risk Factors in SLE: Multivariate Regression Analysis in 16,409 Patients

Background : We assessed factors associated with cancer risk in systemic lupus erythematosus (SLE), relative to the general population, using a large international multi-centre clinical cohort (30 centres, 16,409 patients). Methods : Cancers were ascertained by registry linkage. We used Poisson hierarchical regression to assess for potential independent effects of sex, race/ethnicity, age group, SLE duration, and calendar-year period on the standardized incidence ratios (SIR; ratio of cancers observed to expected). The hierarchical model allowed for differences in effects across countries. The primary regression analyses were done using the overall cancer SIRs; in secondary analyses we focused on hematological cancer SIRs. Results : In adjusted analyses, we demonstrated lower SIR estimates for overall cancer risk, in black versus white SLE patients, in SLE patients of older versus younger age, and for patients with SLE duration of 5 years or more (versus lower duration). Female sex and calendar year were not clearly associated. Regarding hematological cancers specifically, SLE duration of 5 years or more again appeared to be associated with lower SIR estimates. Conclusion : Cancer risk in SLE is increased relative to the general population; this is particularly true for patients of white race/ethnicity, younger age, and of shorter SLE duration.