Hospitalization for Inflammatory Bowel Disease is Associated with Increased Risk of Breast Cancer: A Nationwide Cohort Study of an Asian Population.

PURPOSE: To learn whether women with inflammatory bowel disease (IBD) exhibit a higher risk of breast cancer. METHODS: We identified 4,856 women with IBD symptoms from 1998 to 2008 and 19,424 control patients without the disorder, frequency matched by age, sex, and admission year. Both cohorts were followed-up until the end of 2010 to estimate the risk of breast cancer. RESULTS: Overall, the incidence of breast cancer was similar in the IBD and control cohorts (1.31 vs. 1.25 per 1,000 person-years). The adjusted hazard ratio of breast cancer was 0.95 (95 % confidence interval 0.66-1.36) for the IBD patients. Further analysis revealed that neither Crohn disease nor ulcerative colitis was associated with the risk of developing breast cancer in women. The age-specific analysis indicated that the incidence of breast cancer was highest in the 45- to 65-year-old age group in both cohorts. The incidence of breast cancer was significantly increased in patients who required hospitalization twice or more per year, compared with the control cohort (adjusted hazard ratio 8.45; 95 % confidence interval 4.64-15.4). Moreover, age-specific analysis showed that patients aged less than 65 years old (≤44 or 45-65 years of age) exhibited a strong association between IBD hospitalization and breast cancer risk. CONCLUSIONS: The risk of breast cancer was positively proportional to the frequency of admission for IBD. Therefore, careful surveillance of breast cancer should be sought for female IBD patients with 2 or more annual hospitalizations.