AbstractBackgroundThe overall risk of colorectal cancer in Crohn's disease (CD) is higher than in the general population, and CD‐associated cancer (CDAC) has poorer prognosis than sporadic cancer. Developing treatment strategies for improving the prognosis of CDAC, we evaluated the characteristics of CDAC according to the underlying disease behavior, namely stricturing and penetrating.MethodsThis multicenter retrospective study comprises 316 CDAC patients who underwent surgery between 1985 and 2019. Clinicopathological findings including disease behavior and oncological outcomes were investigated.ResultsThere was no association between the preoperative course of CDAC patients and disease behavior; however, postoperative information revealed distinctly different characteristics between CDAC patients with stricturing behavior and those with penetrating behavior (stricturing with lymphatic invasion and peritoneal dissemination recurrence, and penetrating with histologically poorly differentiated and local recurrence). Oncological outcome of patients with CDAC was distinctly different according to disease behavior, as penetrating provided a poor outcome (overall survival [OS]:p= 0.02; relapse‐free survival [RFS]:p= 0.002) whereas stricturing had no effect. Furthermore, penetrating behavior was identified as one of the independent risk factors for poor OS and RFS (OS: hazard ratio [HR] 1.89, 95% confidence interval [CI] 1.16–3.09,p= 0.01; RFS: HR 2.15, 95% CI 1.28–3.63,p= 0.004).ConclusionsOur study highlights the different characteristics of CDAC according to the underlying disease behavior and substantiates the poor prognosis of CDAC patients with penetrating behavior. Treatment planning including screening, surgical procedures, and postoperative treatment, with awareness of these findings, may contribute to improved prognosis for CDAC patients.