Background: We explored the clinical characteristics, treatment, and outcomes of colitis-associated colorectal cancer (CAC) and compared with sporadic colorectal cancer in Taiwan.

Methods: In this retrospective study spanning 1987-2022, CACs diagnosed according to endoscopic and pathological reports from 14 tertiary centers were reported to our cohort. Clinical demographics, endoscopic findings, histological results, treatment modalities, and outcomes were analyzed. Sporadic colorectal cancer data were retrieved from the Cancer Registry Annual Report, Ministry of Health and Welfare, Taiwan.

Results: We enrolled 65 patients with CAC (median age: 56 years; male: 66.2%). Distal colon was the most common tumor location (41.5%). Of patients with ulcerative colitis, 77.2% had extensive colitis, and 76.5% had Mayo endoscopic subscores of ≥2. Moreover, 50% of lesions were nonpolypoid with indistinct borders in 66.7%. Signet-ring cell subtype consisted of 12.3%. Surveillance colonoscopy adherence was 78.4%, yet 51.3% interval cancers occurred. Disease stage 0-4 distribution was 15%, 20%, 13.3%, 20%, and 31.7%, respectively. Endoscopic resection was feasible for 14%, whereas 67.7% required surgery. During follow-up (median: 21.5 months), we recorded 23.2% recurrence and 34.5% mortality. Lesions with indistinct borders were associated with adverse outcomes (adjusted odds ratio = 11.5 [1.35-98.16]). Colitis-associated rectal cancers, diagnosed later ( P < 0.001), had worse outcomes than sporadic rectal cancers.

Conclusions: This is the largest Asian CAC cohort study, emphasizing the need for stringent disease control, improving detection, and reducing interval cancers. Signet-ring cell subtype was prevalent. Rectal colitis-associated cancers were diagnosed later with poorer outcomes than sporadic rectal cancers.