Colorectal adenocarcinoma patients with M1a diseases gain more clinical benefits from palliative primary tumor resection than those with M1b diseases: A propensity score matching analysis

Table 1 Baseline characteristics of metastatic colorectal adenocarcinoma patients

Variable	Total (n = 19680) (%)	M1a (n = 10399) (%)	M1b (n = 9281) (%)	P value1
Gender
Female	8573 (43.6)	4462 (42.9)	4111 (44.3)	0.050
Male	11107 (56.4)	5937 (57.1)	5170 (55.7)
Year of diagnosis				< 0.001
2010-2012	9835 (50.0)	5342 (51.4)	4493 (48.4)
2013-2015	9845 (50.0)	5057 (48.6)	4788 (51.6)
Age (years)				< 0.001
< 65	10680 (54.3)	5507 (53.0)	5173 (55.7)
≥ 65	9000 (45.7)	4892 (47.0)	4108 (44.3)
Race				0.011
White	14715 (74.8)	7856 (75.5)	6859 (73.9)
Black	3033 (15.4)	1578 (15.2)	1455 (15.7)
Others	1932 (9.8)	965 (9.3)	967 (10.4)
Marital status				0.661
Married	9774 (49.7)	5180 (49.8)	4594 (49.5)
Others	9906 (50.3)	5219 (50.2)	4687 (50.5)
Primary site				0.027
Colon	15476 (78.6)	8114 (78.0)	7362 (79.3)
Rectum	4204 (21.4)	2285 (22.0)	1919 (20.7)
Grade				< 0.001
I + II2	11321 (57.5)	6525 (62.7)	4796 (51.7)
III + IV3	3889 (19.8)	1909 (18.4)	1980 (21.3)
Others	4470 (22.7)	1965 (18.9)	2505 (27.0)
Surgery				< 0.001
Yes	9360 (47.6)	5787 (55.6)	3573 (38.5)
No	10320 (52.4)	4612 (44.4)	5708 (61.5)
Chemotherapy				0.415
Yes	14057 (71.4)	7402 (71.2)	6655 (71.7)
No/unknown	5623 (28.6)	2997 (28.8)	2626 (28.3)
Radiotherapy
Yes	975 (5.0)	670 (6.4)	305 (3.3)	< 0.001
No	18705 (95.0)	9729 (93.6)	8976 (96.7)

¹χ² test.

²Well or moderately differentiated tumors.

³Poorly differentiated or undifferentiated tumors.

Table 2 Univariate and multivariate cox regression analyses for overall survival of metastatic colorectal adenocarcinoma patients

	M1a				M1b
	Univariate analysis		Multivariate analysis		Univariate analysis		Multivariate analysis
	HR (95%CI)	P value	HR (95%CI)	P value	HR (95%CI)	P value	HR (95%CI)	P value
Gender
Female	Reference		Reference		Reference		Reference
Male	1.100 (1.054-1.147)	< 0.001	1.025 (0.975-1.077)	0.339	1.043 (1.002-1.086)	0.042	1.020 (0.972-1.070)	0.428
Year of diagnosis
2010-2012	Reference		Reference		Reference		Reference
2013-2015	0.972 (0.929-1.016)	0.208	0.981 (0.929-1.036)	0.486	0.965 (0.925-1.006)	0.096	0.972 (0.924-1.023)	0.277
Age (years)
< 65	Reference		Reference		Reference		Reference
≥ 65	1.675 (1.606-1.746)	< 0.001	1.413 (1.344-1.485)	< 0.001	1.527 (1.466-1.589)	< 0.001	1.319 (1.256-1.385)	< 0.001
Race
White	Reference		Reference		Reference		Reference
Black	1.138 (1.075-1.206)	< 0.001	1.114 (1.042-1.192)	0.002	1.127 (1.068-1.191)	< 0.001	1.137 (1.064-1.215)	< 0.001
Others	0.910 (0.844-0.981)	0.013	0.864 (0.792-0.942)	0.001	0.953 (0.891-1.020)	0.164	0.952 (0.878-1.031)	0.227
Marital status
Married	Reference		Reference		Reference		Reference
Others	1.326 (1.272-1.383)	< 0.001	1.142 (1.086-1.201)	< 0.001	1.212 (1.165-1.262)	< 0.001	1.078 (1.026-1.132)	0.003
Primary site
Colon	Reference		Reference		Reference		Reference
Rectum	0.799 (0.758-0.841)	< 0.001	0.759 (0.711-0.811)	< 0.001	0.839 (0.797-0.882)	< 0.001	0.779 (0.731-0.830)	< 0.001
Grade
I + II	Reference		Reference		Reference		Reference
III + IV	1.530 (1.450-1.614)	< 0.001	1.580 (1.484-1.682)	< 0.001	1.447 (1.375-1.523)	< 0.001	1.506 (1.417-1.601)	< 0.001
Others	1.702 (1.614-1.795)	< 0.001	1.149 (1.074-1.228)	< 0.001	1.544 (1.473-1.619)	< 0.001	1.178 (1.109-1.251)	< 0.001
Surgery
Yes	Reference		Reference		Reference		Reference
No	1.953 (1.859-2.051)	< 0.001	2.133 (2.011-2.262)	< 0.001	1.632 (1.552-1.716)	< 0.001	1.955 (1.843-2.074)	< 0.001
Chemotherapy
Yes	Reference		Reference		Reference		Reference
No/unknown	2.520 (2.395-2.651)	< 0.001	2.282 (2.164-2.405)	< 0.001	2.558 (2.430-2.692)	< 0.001	2.565 (2.432-2.705)	< 0.001
Radiotherapy
Yes	Reference		Reference		Reference		Reference
No	2.337 (2.069-2.639)	< 0.001	1.236 (1.085-1.408)	0.001	1.695 (1.465-1.961)	< 0.001	0.946 (0.813-1.101)	0.472

HR: Hazard ratio; CI: Confidence interval.

Table 3 Survival time for metastatic colorectal adenocarcinoma patients with or without palliative primary tumor resection

	Median survival time (95%CI)	1-yr survival rate (%)	3-yr survival rate (%)
M1a (total)
No surgery	14 (13.275-14.725)	54.4	13.9
Surgery	23 (21.977-24.023)	70.4	32.6
M1a (liver metastasis)
No surgery	14 (13.320-14.780)	53.8	13.4
Surgery	22 (20.955-23.045)	69.2	29.8
M1a (lung metastasis)
No surgery	18 (15.692-20.308)	62.2	18.6
Surgery	33 (28.014-37.986)	77.5	45.4
M1b
No surgery	10 (9.401-10.599)	42.2	8.6
Surgery	17 (16.209-17.791)	60.0	20.4