Analysis of clinicopathological features and oncological outcomes of ulcerative colitis-associated colorectal cancer based on macroscopic classification.

[PURPOSE] Few studies have reported the association of macroscopic classification with clinicopathological characteristics and prognosis of ulcerative colitis-associated colorectal cancer (UC-CRC), unlike sporadic CRC. In this study, we aimed to clarify the clinical significance of macroscopic classification of UC-CRC.

[METHODS] The cohort included 480 patients with UC-CRC with invasion beyond the muscularis propria treated at 43 Japanese institutions between 1983 and 2023. The patients were divided into six groups based on the macroscopic type (types 0-5), and clinicopathological features and prognoses were compared.

[RESULTS] Among 480 patients, 66 (13.8%), 75 (15.6%), 116 (24.2%), 63 (13.1%), 68 (14.2%), and 92 (19.2%) had type 0-5 tumors, respectively. There were significant differences in the clinicopathological characteristics with a younger age in type 4 or 5 tumors than in type 2 tumors (p < 0.01) and a higher frequency of undifferentiated carcinomas (p < 0.01) and lymph node metastasis (p < 0.01) and more advanced depth of invasion (p < 0.01) in type 4 tumors than in type 1 or 2 tumors. Type 4 and 5 were independent risk factors for 5-year recurrence-free survival (p = 0.02; type 4 [HR: 6.35], type 5 [HR: 5.25]) and type 0, 4, and 5 for overall survival (p = 0.02; type 0 [HR: 4.51], type 4 [HR: 5.70], type 5 [HR: 4.02]).

[CONCLUSIONS] Type 0, 4, and 5 tumors were characteristic macroscopic types of UC-CRC and correlated with worse prognosis. Therefore, endoscopic diagnosis of the macroscopic type of UC-CRC might be helpful in determining tumor aggressiveness.