Objective: To compare the clinicopathological features and prognosis between left-sided colon cancer (LC) and right-sided colon cancer (RC).
Methods: Clinicopathological and follow-up data of 2 174 colon carcinoma cases undergoing resection at Shanghai Changhai Hospital of The Second Military Medical University from January 2000 to December 2010 were retrospectively analyzed. Patients with transverse colon cancer, overlapping position, unknown location, recurrent cancer, multiple primary cancer, concomitant malignant tumors, preoperative chemotherapy, local resection, incomplete clinical data and missed follow up were excluded. Finally, a total of 1 036 patients, whose primary tumors were radically removed, were enrolled, with 563 patients in LC group (including carcinoma in cecum, ascending colon and hepatic flexure) and 473 in RC group (including carcinoma in splenic flexure, descending colon and sigmoid colon). The clinicopathological features and survival, including median overall survival, 5-year overall survival rate, tumor specific median overall survival, cancer specific 5-year overall survival rate, were compared between LC and RC groups. Tumor specific overall survival was defined as the period between operation date to the date of death caused by cancer progression. Multivariate Cox regression analysis was used to analyze the influencing factors of survival. Propensity score matching was carried out to balance the clinicopathological factors between the two groups with the SAS 9.3, taking the following parameters into consideration (age, gender, gross appearance, tumor diameter, invasion depth, lymph node metastasis, distant metastasis, TNM stages, differentiation, CEA and CA199-9). Patients in RC group and LC group were matched according to the propensity scores and the clinicopathological characteristics and prognosis of two groups were compared again.
Results: No significant differences were identified between the two groups in age, distant metastasis and serum CEA level. Compared with RC group, LC group had more male patients [60.9%(343/563) vs. 51.0%(241/473), P=0.001], more ulcerative tumors [71.9% (405/563) vs. 65.3%(309/473), P=0.006], better differentiation [well/moderately differentiated: 87.5%(493/563) vs. 73.8%(349/473), P=0.000], lower infiltration depth [T1-2: 17.1%(96/563) vs. 10.1%(48/473), P=0.001], higher lymph node metastasis rate [N0: 53.3%(300/563) vs. 62.4%(295/473), P=0.013], lower TNM stage [stage I(: 13.3%(75/563) vs. 7.8%(37/473), P=0.000], lower serum CA199 level [<37 kU/L: 68.4% (385/563) vs. 62.6% (296/473), P=0.022] and smaller tumor diameter [<5.0 cm: 55.1%(310/563) vs. 38.3%(181/473), P=0.000]. The median overall survival was 82 months and 76 months in LC and RC groups, respectively, and the 5-year overall survival rate was 58.3% and 50.9%(P=0.038). The median tumor specific survival was 84 months and 78 months in LC and RC groups, respectively, and the 5-year tumor specific overall survival rate was 60.6% and 52.9% (P=0.031). Multivariate Cox regression analysis showed that tumor location (LC vs. RC) was not associated with overall survival (P=0.106) and tumor specific survival (P=0.091). After propensity score matching, no significant difference was found in clinicopathological factors and propensity score (0.458±0.129 vs. 0.459±0.129, P=0.622) between LC and RC group. After matching, there was no significant difference in overall survival rate (54.0% vs. 51.7%, P=0.982) and tumor specific overall survival rate(56.4% vs. 53.1%, P=0.819) between two groups.
Conclusion: Significant difference exists between RC and LC in clinicopathological factors, but not in survival.