Objective: To investigate the relative risk of cancer among patients with chronic urticaria in the Taiwanese population.
Design: Retrospective population-based cohort study.
Setting: The National Health Insurance Research Database of Taiwan from January 1, 1996, through December 31, 2008.
Participants: A total of 12,720 patients with chronic urticaria, with long-term antihistamine use and no history of malignant tumors, autoimmune diseases, atopy, or allergic diseases.
Main outcome measure: Relative cancer risk calculated by standardized incidence ratios.
Results: There were 704 cancers among chronic urticaria patients. An increased risk of cancer (standardized incidence ratio, 2.2; 95% CI, 2.0-2.3), especially hematologic malignant tumor (4.1; 3.1-5.4), was observed. The relative risk of cancer varied by age and was highest among those aged 20 to 39 years in comparison with the general population. Most cancer cases were detected within the first year of diagnosis. The risk of non-Hodgkin lymphoma was greatest (standardized incidence ratio, 4.4; 95% CI, 3.0-6.1) among the hematologic cancers.
Conclusions: Patients with chronic urticaria are at increased risk of cancer, especially hematologic malignant tumors. Further studies are needed to delineate the associations.