P642. Anorectal cancer associated with Crohn's disease
Like ulcerative colitis, patients with Crohn's disease have increased risk of developing colorectal cancer in comparison with the background population. In Western countries, colorectal cancer associated with Crohn's disease is predominant in right-side colon, whereas in Japan, approximately 70% of the cancer was located in rectum and anus. This study aimed to clarify the clinicopathological difference between anorectal cancer and the other colorectal cancer in Crohn's disease.
A literature search was performed using Ichushi (Japanese medical literature database) between 1983 and December, 2011 for colorectal cancer associated with Crohn's disease. One hundred and seventy-four cases were picked up, and seven cases were excluded, because the location of the tumor was not documented precisely. Therefore, 167 cases were used for analysis. The cases were classified to two groups: the cancer was located in rectum or anus [RA group (n = 115)] and elsewhere [control: C group (n = 52)].
The location of the tumor was rectum (57%) and anus (43%) in RA group, whereas it was right colon (54%) and left colon (46%) in C group. The age at cancer diagnosis was younger in RA group [41 (25–89); median (range)] than in C group [47 (25–84); p < 0.027]. The duration of Crohn's disease was longer in RA group (0–39 (16) years) than C group (2 (0–37) years; p < 0.0001). The proportion of penetrating behavior was higher in RA group than in C group (55.8% vs. 31.0%; p = 0.16). Examination under anesthesia revealed cancer in 16% in RA group preoperatively. The diagnosis had not obtained as cancer in 19% (RA group) and 38% (C group) before operation with statistical significance (p = 0.013). The proportion of well differentiated carcinoma was lower in RA group than in C group (22% vs. 48%; p = 0.003), and mucinous histology was more predominant in RA group (62% vs. 21%; p < 0.0001). The proportion of the patients according to the clinical stage (0:1:2:3:4) was 1%:9%:34%:30%:26% in RA group and 3%:16%38%:32%:11% in C group, and the difference was statistically significant (p = 0.046).
Anorectal cancer associated with Crohn's disease was more advanced in stage. Early detection of such tumors is needed.