本研究旨在评估一级亲属炎症性肠病（IBD）史与结肠直肠癌（CRC）风险之间的关联。我们在瑞典开展了一项全国性病例对照研究，包括69,659例CRC病例和343,032例与年龄、性别、出生年份和所在县匹配的非CRC对照组。通过连接多代登记和全国ESPRESSO（瑞典组织病理报告增强流行病学）队列，我们确定了指标个体双亲、全同胞和后代中的IBD诊断。使用条件 logistic 回归计算了与IBD家族史相关的CRC的奥斯瑞比（OR）。在CRC病例（1566/69659）和对照组（7676/343027）中，均有2.2%以上的人具有≥1个有IBD史的一级亲属。在调整了CRC家族史后，我们观察到没有IBD患者的一级亲属中CRC风险的增加（OR，0.96；95%CI，0.91-1.02）。这种零关联对于IBD亚型（克罗恩病或溃疡性结肠炎）、有IBD史的一级亲属人数（1或≥2）、IBD首次诊断时的年龄（<18岁、18-39岁、40-59岁或≥60岁）、IBD最大部位/范围或一级亲属关系（父母、兄弟姐妹或子女）都是一致的。这种零关联在早发性CRC（年龄<50岁诊断）中仍然存在。总之，一级亲属的IBD史与CRC的风险没有关联。我们的研究结果表明，在IBD患者的子女、兄弟姐妹或父母中不需要进行额外的CRC筛查，并加强了这样一个理论，即IBD患者实际上是由于结肠炎症或不典型而增加了CRC的风险。©2023 UICC。

This study aims to assess the association between inflammatory bowel disease (IBD) history in first-degree relatives (FDRs) and colorectal cancer (CRC) risk. We conducted a nationwide case-control study in Sweden among 69 659 CRC cases and 343 032 non-CRC controls matched on age, sex, birth year and residence county. Through linkage of multi-generation register and the nationwide ESPRESSO (Epidemiology Strengthened by histoPathology Reports in Sweden) cohort, we ascertained IBD diagnoses among parents, full siblings and offspring of the index individuals. Odds ratios (ORs) of CRC associated with IBD family history were calculated using conditional logistic regression. 2.2% of both CRC cases (1566/69659) and controls (7676/343027) had ≥1 FDR with IBD history. After adjusting for family history of CRC, we observed no increased risk of CRC in FDRs of IBD patients (OR, 0.96; 95%CI, 0.91-1.02). The null association was consistent according to IBD subtype (Crohn's disease or ulcerative colitis), number of FDRs with IBD (1 or ≥ 2), age at first IBD diagnosis in FDRs (<18, 18-39, 40-59 or ≥60 years), maximum location/extent of IBD or FDR relation (parent, sibling or offspring). The null association remained for early-onset CRC (diagnosed at age <50 years). In conclusion, IBD history in FDRs was not associated with an increased risk of CRC. Our findings suggest that extra screening for CRC may not be needed in the offspring, siblings or parents of IBD patients, and strengthen the theory that it is the actual inflammation or atypia of the colon in IBD patients that confers the increased CRC risk.© 2023 UICC.