Abstract Background Patients with inflammatory bowel disease (IBD) are known to have an altered risk for various malignancies. However, comprehensive data on sex-specific differences in this risk profile are limited. This study aimed to quantify and compare the overall and site-specific malignancy risks in male versus female patients with IBD using a large, nationwide population-based cohort. Methods We conducted a retrospective cohort study using South Korea’s Health Insurance Review and Assessment Service (HIRA) claims database from 2007 to 2023. We identified 66,392 IBD patients (20,503 Crohn’s disease CD, 45,889 ulcerative colitis UC) with no history of prior malignancy. The cohort consisted of 42,809 (64.5%) males and 23,583 (35.5%) females, with a median follow-up of 6.6 years. Standardised incidence ratios (SIRs) and 95% confidence intervals (CIs) were calculated by comparing the observed number of malignancies to the expected number based on the general population. Results Overall, the IBD cohort showed a slightly reduced risk for malignancy (SIR 0.92, 95% CI 0.87-0.96). However, significant divergence between sexes were noted. Males showed reduced risk (SIR 0.80, 95% CI 0.75–0.85) whereas females had increased risk (SIR 1.13, 95% CI 1.05–1.21) (Table 1, 2). In males, significantly decreased overall malignancy risk was driven by lower-than-expected rates of common cancers like colorectal (SIR 0.69), stomach (SIR 0.55), and lung (SIR 0.74) cancer. In contrast, a significantly increased overall malignancy risk in female patients with IBD was associated with elevated risks for breast (SIR 1.35), cervix (SIR 1.49), and ovarian (SIR 1.98) cancers. Furthermore, while males had a reduced risk, female patients with IBD had no reduction in colorectal cancer risk (SIR 1.01). Both sexes shared significantly elevated risks for haematologic malignancies, including non-Hodgkin lymphoma (Male SIR 2.59; Female SIR 2.89) and leukaemia (Male SIR 2.00; Female SIR 2.12), with risks being particularly high in CD. Both sexes also showed increased risks for small intestine cancer and anal canal cancer. Conclusion This large, nationwide study demonstrates a sex-based disparity in malignancy risk for IBD patients. Male patients with IBD had a lower overall cancer burden compared to the general population, whereas female patients faced an increased overall risk. This increase in females appears driven by gynaecological cancers and an absence of the risk reduction for colorectal cancer seen in male patients. These findings highlight the need for sex-specific cancer surveillance strategies, emphasising vigilance for haematologic, specific gastrointestinal, and gynaecological malignancies in female patients with IBD. References: 1. Gordon H, Biancone L, Fiorino G, et al. ECCO Guidelines on Inflammatory Bowel Disease and Malignancies. J Crohns Colitis. 2023;17(6):827-854. doi:10.1093/ecco-jcc/jjac187 2. Scharl S, Barthel C, Rossel JB, et al. Malignancies in Inflammatory Bowel Disease: Frequency, Incidence and Risk Factors-Results from the Swiss IBD Cohort Study. Am J Gastroenterol. 2019;114(1):116-126. doi:10.1038/s41395-018-0360-9 3. Jung YS, Han M, Park S, Kim WH, Cheon JH. Cancer Risk in the Early Stages of Inflammatory Bowel Disease in Korean Patients: A Nationwide Population-based Study. J Crohns Colitis. 2017;11(8):954-962. doi:10.1093/ecco-jcc/jjx040 4. Kim HM, Kim JH, Lee JK, et al. Age- and sex-specific risk of colorectal cancer in incident ulcerative colitis during the first 10 years after diagnosis: a nationwide population-based study. Scand J Gastroenterol. 2021;56(11):1279-1285. doi:10.1080/00365521.2021.1958370 Conflict of interest: Dr. Seo, Jeongkuk: No conflict of interest Lee, Ju Won: No conflict of interest Kim, Kyuwon: No conflict of interest Jung, Sun-Young: No conflict of interest Choi, Chang Hwan: No conflict of interest
Seo et al. (Thu,) studied this question.