Classification of rectal cancer according to recurrence types - Comparison of Japanese guidelines and Western guidelines-

Abstract ObjectivesLocal recurrence (LR) and lung metastasis are more common in rectal cancer than in colon cancer. However, the diagnosis of rectal cancer is not standardized as there is no global consensus on its definition and classification. The classification of rectal cancer differs between Japanese and Western guidelines. Thus, we aimed to elucidate how rectal cancer is classified by investigating the relationship between rectal cancer localization and recurrence in the patientsMethods A total of 958 patients with cStage II and III colorectal cancer were included in the analysis: 323 with right-sided colon cancer (RC), 284 with left-sided colon cancer (LC), and 351 with rectal cancer. Localization of rectal cancers was assessed by enema examination and rigid endoscopy. Results There were no significant differences between rectal Rs, RC and LC in rates of liver and lung metastasis or LR . Lung metastasis or LR were significantly more common among Rab rectal cancers (in Japan) than among right-sided and left-sided colon cancers (p=0.0043, p=0.0002). Lung metastases and LR occurred at significantly higher rates in rectal cancers measuring ≤12 cm and ≤10 cm than in colon cancers (p=0.0117, p=0.0467, p=0.0036, p=0.0010 respectively). Finally, the liver and lung metastases and LR rates of rectal cancers measuring 11 to 15 cm were 6.9%, 2.8%, and 5.7%, respectively. This indicated Equivalent to colon cancer . Conclusions The upper rectum may have the same treatment strategies as the colon cancer. There was no difference in the classification of colorectal cancer between Japan and western countries