Clinicopathological factors	Variables	Postoperative adjuvant chemotherapy		P-value
Clinicopathological factors	Variables	Present (n = 162)	Absent (n = 72)
Age	≥75	15	27	<0.001
Age	<75	147	45	<0.001
Gender	Male	96	36	0.20
Gender	Female	66	36	0.20
Location	Proximal	51	19	0.54
Location	Distal	111	53	0.54
Preoperative CEA	Elevated	71	30	0.78
Preoperative CEA	Normal	91	42	0.78
Differentiation	Low grade^a	151	67	>0.99
Differentiation	High grade^b	11	5	>0.99
Invasion depth	T1 - T3	94	55	0.008
Invasion depth	T4	68	17	0.008
Lymphatic invasion	None-mild	46	32	0.02
Lymphatic invasion	Moderate-severe	116	40	0.02
Venous invasion	None-mild	79	52	0.001
Venous invasion	Moderate-severe	83	20	0.001
No. of dissected lymph nodes	≥12	129	53	0.31
No. of dissected lymph nodes	<12	33	19	0.31
TNM classification, 7^th edition	IIIA, IIIB	129	63	0.20
TNM classification, 7^th edition	IIIC	33	9	0.20