Surgery for Colorectal Cancer Associated with Crohn's Disease-Toward a Medical Treatment Strategy Based on the Differences Between Japan and Western Countries

With advances in the treatment of Crohn's disease (CD), the number of long-term cases is increasing, along with the incidence of CD-related cancers. Here, we discuss the clinical features, diagnosis, treatment, prognosis, and surveillance of CD-related cancers. There are regional differences in the common sites and histological types of CD-related cancers, with right-sided colon cancer accounting for 40% of cases in Europe and the US, and squamous cell carcinoma being common. In Japan, rectal and anal cancers account for 80% of cases, and mucinous carcinoma is common. The prognosis of CD-associated colon cancer and sporadic colon cancer is the same; however, the prognosis of CD-associated rectal cancer is clearly worse than that of sporadic rectal cancer. Early diagnosis is important to improve the prognosis of CD-associated rectal cancer, and it is necessary to establish a surveillance method for CD-associated cancer that combines colonoscopy, anesthetic proctoscopy, and imaging, as appropriate. The basic treatment for CD-related cancer is surgical resection; however, the criteria for selecting the surgical procedure are unclear, and there is no clear evidence for multidisciplinary perioperative treatment including chemotherapy and radiotherapy. Additionally, CD-related rectal and anal cancers have a higher local recurrence rate than that of sporadic rectal cancers; therefore, thorough local control is important. Furthermore, CD-related cancers have different epidemiologies in different regions; therefore, unique diagnostic and treatment strategies must be established for each region.