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.