MALIGNANCY RISK IN MALE PATIENTS WITH ANKYLOSING SPONDYLITIS

Abstract

Background: In recent studies, the association between autoimmune disease and malignancy has been reported. However in Ankylosing spondylitis (AS), a chronic inflammatory rheumatic disease with marked male predominance, the evidence of this relationship is scarce and inconsistent.

Objectives: To determine the overall cancer and site-specific cancer risk in male patients with AS.

Methods: Using the claims database of Health Insurance and Review Assessment (HIRA), male patients with AS without prior cancer history between 2012 and 2014 were enrolled (n=21,780). For the control group, male general population, stratified random samples of claims data were used (n=342,361). All individual was observed up to the development of any cancer, or end of the study period (December 31, 2015). Incidence rates (IR) of overall and site-specific cancer were presented as the number of event per 10,000 person-years. To make fairer comparison between AS patients and general population, we calculated age adjusted incidence ratio by dividing cancer event of general population with corresponding age. The standardized incidence ratio (SIR) was used to represent the association between AS and cancer, accounting for person-years at risk.

Results: During 71,046 person-year, total 552 cases of cancer occurred in male AS group. Prostate cancer was the leading type of cancer in male AS patients (101 cases, IR 14.22, 95% CI 11.44-16.99). And it was followed by liver cancer (70 cases, IR 9.9, 95% CI 7.5-12.2), lung cancer (48 cases, IR 6.8, 95% CI 4.9-8.7), colorectal cancer (45 cases, IR 6.3, 95% CI 4.5-8.2) and stomach cancer (43 cases, IR 6.1, 95% CI 4.2-7.9). Compared to general population, the overall incidence of cancer was increased in male patients with AS (SIR 1.25, 95% CI 1.14-1.36). At a specific malignancy type, the risk of pancreas cancer (SIR 1.75, 95% CI 1.12-2.37) and malignancy of male reproductive system were increased (SIR 1.97, 95% CI 1.59-2.35).