Objective To analyze the clinicopathological features and prognosis of middle-aged and elderly patients with left and right colon cancer after operation, and to provide theoretical basis for the implementation of individualized treatment for elderly patients.

Methods The gender, age, tumor site, pathological type, pTNM (postoperative TNM) stage, lymph node metastasis and other data of 176 patients with colon cancer diagnosed pathologically after surgery in Affiliated Hospital of Yangzhou University from January 2012 to December 2015 were collected. Patients with tumors locating in the transverse colon, hepatic region of colon, ascending colon, and ileocecal region were classified as right half colon cancer group (88 cases), and those with the tumors locating in the sigmoid colon, descending colon, and splenic region of colon were classified as left half colon cancer group (88 cases). The pathological features of left and right colon cancer were observed, and their prognosis of patients was analyzed by univariate and multivariate analysis, and the expression of mismatched repair (MMR) protein and postoperative survival time of the two groups were observed.

Results There were statistically significant differences in age, tumor diameter, TNM stage and MMR protein expression level between the two groups (P < 0.05). Of the 176 patients, 128 were positive for mismatched repair defects (pMMR) protein, accounting for 72.73%. The expression of mismatched repair complete (dMMR) protein was found in 48 patients, accounting for 27.27%. The expression of dMMR protein was found in 18 cases (20.45%) and pMMR protein expression in 70 cases (79.55%). The expression of dMMR protein was found in 30 patients (34.09%) with right colon cancer, and in 58 patients (65.91%) with pMMR protein expression. There were statistically significant differences between dMMR and pMMR protein expression between elderly patients with left colon cancer and those with right colon cancer (P < 0.05). COX univariate risk model showed that pT stage, pN stage, pTNM stage, lymph node capsule invasion and tumor site were correlated with prognosis. The results of multifactor risk model showed that pT stage, pN stage and MMR protein expression were independent prognostic factors in elderly patients with colon cancer (P < 0.05). Kaplan-Meier and Log-rank survival analysis results showed that the overall survival time of all patients and those with pTNM stage Ⅰ to Ⅱ and pTNM stage Ⅲ to Ⅳ in the left colon cancer group showed statistically significant difference compared with those in the right colon cancer group (P < 0.05).

Conclusion The survival time of left-sided colon cancer in elderly patients is longer than that of right-sided colorectal cancer, which is considered to be related to the molecular typing and biological behavior of left- and right-sided colorectal cancer, and it is also a clinical prognostic factor.