At present, more and more evidence shows that colon and rectal cancers are different diseases. There are many differences no matter in the epidemiology, anatomy and histology, molecular characteristics, transfer patterns, or clinical treatment methods, therapeutic effects and prognosis. In clinical treatment, it cann’t be considered as the same disease in general. Through the retrospective analysis of the three clinical studies of CALGB/SWOG 80405, CRYSTAL, and FIRE-3, it has been found that there were significant differences in the efficacy of cetuximab and bevacizumab in left and right colon cancer. Based on the above clinical trials, the National Cancer Institute for the United States (NCCN) for the first time includes the guidelines for the impact of primary sites on the treatment of colon cancer into guidelines in 2017. In the current era of advocating precision and individualized treatment, to clarify the pathogenesis, histological differences and clinical response to drugs in colon cancer and rectal cancer, can not only reduce the economic burden of patients, but also provide the most scientific basis for the precise treatment of patients gradually.

[Abstract] Objective: To compare the differences in clinical and pathological features and survival time between patients with left -sided colon cancer and rectal cancer. Methods:Atotal of 323 patients with colorectal cancer (CRC) underwent surgical resection at Changhai Hospital of the Second Military Medical University between January 2011 and January 2012 were enrolled in this study. The clinical data of patients were collected and the follow-up was started from the day of surgery or pathological confirmation with the death of patients as endpoints. The follow-up lasted untilAugust 1,2017. Results: There were significant differences in initial symptoms, pathologic type, tumor stage, anemia before surgery, p53 positive rate, and BRAF mutation (χ2=59.088， 4.188， 24.305， 11.956， 4.221， 4.001， all P<0.05) between patients with left-sided colon cancer and rectal cancer. For all the patients, the median survival time was not observed. The five-year survival rates of patients with left-sided colon cancer and rectal cancer were 79.2% and 74.3%, respectively. The Kaplan-Meier survival curves of patients at StageⅠ-Ⅱshowed that there was no statistical difference between patients with left-sided colon cancer and rectal cancer（P=0.840） and the survival of Stage Ⅲ patients between the two groups also showed no statistical difference (P=0.106). Cox regression analysis showed that both the pathologic types [HR=1.759, P=0.047] and tumor stage [HR=2.104, P<0.001] were independent predictive factors for OS of CRC patients. Conclusion: There were no differences in survival time between patients with left-sided colon cancer and rectal cancer. The pathologic types and tumor stage were factors influencing the OS of CRC patients.