Table 1. Demographics of patients in the recurrence study.

Variable	Total		Training Set		Test Set		p value
	n = 235	%	n = 157	%	n = 78	%
Age (Mean ± SD)	67.8 ± 11.7		68.7 ± 11.2		66.0 ± 12.5		0.516
Follow-up (Months± SD)	65.1 ± 23.6		64.5 ± 24.3		66.5 ± 22.0		0.718
Gender
Male	145	61.7	100	63.7	45	57.7
Female	90	38.3	57	36.3	33	42.3	0.373
Location							0.561
Right colon	68	28.9	47	29.9	21	26.9
Left colon	106	45.1	67	42.7	39	50.0
Rectum	61	26.0	43	27.4	18	23.1
Preoperative CEA level							0.325
< 5 ng/mL	160	68.1	104	66.2	56	71.8
> 5 ng/mL	64	27.2	47	29.9	17	21.8
NA	11	4.7	6	3.9	5	6.4
Stage							0.984
I	39	16.6	26	16.6	13	16.7
II	196	83.4	131	83.4	65	83.3
Emergent operation							0.640
No	225	95.7	151	96.2	74	94.9
Yes	10	4.3	6	3.8	4	5.1
Mucinous component (> 50%)							0.581
No	228	97.0	153	97.5	75	96.2
Yes	7	3.0	4	2.5	3	3.8
Lymphovascular invasion							0.849
No	222	94.5	148	94.3	74	94.9
Yes	13	5.5	9	5.7	4	5.1
Perineural invasion							0.994
No	229	97.4	153	97.5	76	97.4
Yes	6	2.6	4	2.5	2	2.6
Grade of differentiation							0.726
Well/moderate	221	98.3	154	98.0	77	98.7
Poor/undifferentiated	4	1.7	3	2.0	1	1.3
Lymph nodes harvested							0.456
≥ 12	176	74.9	120	76.4	56	71.8
< 12	59	25.1	37	23.6	22	28.2
Adjuvant chemotherapy*							0.894
Yes	25	10.6	17	10.8	8	10.3
No	210	89.4	140	89.2	70	89.7
Recurrence							0.956
Yes	97	41.3	65	41.4	32	41.0
No	138	58.7	92	58.6	46	59.0

Abbreviations: CEA, carcinoembryonic antigen.

*Only patients who had recurrence despite adjuvant chemotherapy were included in the study. No patients received neoadjuvant therapy.