Differences in epidemiology, pathological features, and molecular pathogeneses have been observed according to primary tumor location in colorectal cancer (CRC). However, predicting CRC survival by tumor location remains controversial. Therefore, we compared the pathological characteristics, molecular features, and prognoses of right-side colon cancer (RCC), left-side colon cancer (LCC), and rectal cancer (RECC) among Chinese patients with CRC. We evaluated 4,426 patients with stage I-III CRC between January 2008 and July 2014from Fudan University Shanghai Cancer Center. All patients were grouped by the locations of tumors (RCC, LCC, and RECC). Patients with RCC were more likely to be women and older, have poorly differentiated tumors, microsatellite repair deficiency (dMMR), negative p53 expression, and the mucinous subtype. Unadjusted Kaplan-Meier survival curves revealed survival in RCC than in LCC and RECC. However, there were no significant differences in OS and DFS between LCC and RECC. The same results were observed for each disease stage. Unadjusted models revealed an increased risk of mortality, recurrence, or metastasis for RCC (OS: HR, 1.68, P=0.0002 and DFS: HR, 1.24, P=0.032), compared to LCC (all stages), and a similar result was observed for stage III patients (OS: HR, 1.79, P<0.0001 and DFS: HR, 1.33, P=0.021). However, adjusted Cox proportional hazard regression models revealed no significant differences in survival between the three tumor locations. Tumor location was not an independent prognostic factor among Chinese patients with stage I-III CRC. But RCCs had a worse prognosis in the dMMR subgroup. The related mechanism remains to be investigated.
Keywords: colorectal cancer; left-sided colon cancer; prognosis; right-sided colon cancer; tumor location.