Supplementary Material for: Clinical characteristics of Crohn's disease-associated cancer with a focus on endoscopic surveillance

Introduction: Long-term Crohn’s disease (CD) increases risk of cancer. However, data on the clinical characteristics and optimal endoscopic surveillance strategies for CD-associated cancers in Japan remain controversial. This study aimed to investigate the clinical characteristics, diagnostic methods, and treatment patterns of CD-associated cancers at our institution, and to consider strategies for effective surveillance in Japanese clinical practice.
Methods: We retrospectively analyzed 21 patients with 26 CD-associated cancer locations treated at our hospital between August 2001 and March 2024, focusing on their clinical backgrounds, cancer characteristics, and endoscopic surveillance practices.
Results: Anorectal cancer was the most common (61%), and 57% were stage II or higher at the time of diagnosis. There were 12 cases of fistula-associated cancer, with a median disease duration of 18.5 years, and 7 cases of stage II or higher. Targeted endoscopic biopsy established the diagnosis in 77%, often requiring multiple-site biopsies. Remission or mild endoscopic activity was observed in 75% (6/8) of stage 0–I patients, compared with 20% (2/10) of stage II–IV patients, suggesting a trend toward more advanced cancer with higher endoscopic activity (P = 0.03). Compared with non-anorectal cancers, 33% of anorectal cancers required four or more endoscopic biopsies for diagnosis, and this rate was significantly higher than that of non-anorectal cancers (P = 0.028).
Conclusion: Anorectal cancer was the most common CD-associated cancer, and strictures and active inflammation made early diagnosis difficult. Annual surveillance with multiple-site biopsies of anal lesions was essential.