Table 1 Baseline characteristics of chemotherapy subgroups before and after propensity score matching
| Â | non-chemotherapy | Chemotherapy | Â | non-chemotherapy | Chemotherapy | Â |
|---|---|---|---|---|---|---|
Variable | n = 19,652 (%) | n = 5458 (%) | p | n = 5458 (%) (PSM) | n = 5458(%) (PSM) | p |
Age | Â | Â | 0.000 | Â | Â | 0.000 |
  > 30 | 57 (0.3) | 57 (1.0) |  | 57 (1.0) | 57 (1.0) |  |
 30–39 | 227 (1.2) | 284 (5.2) |  | 226 (4.1) | 284 (5.2) |  |
 40–49 | 1033 (5.3) | 879 (16.1) |  | 918 (16.8) | 879 (16.1) |  |
 50–59 | 2831 (14.4) | 1574 (28.8) |  | 1640 (30.0) | 1574 (28.8) |  |
 60–69 | 4380 (22.3) | 1552 (28.4) |  | 1407 (25.8) | 1552 (28.4) |  |
 70–79 | 5355 (27.2) | 906 (16.6) |  | 871 (16.0) | 906 (16.6) |  |
  ≥ 80 | 5769 (29.4) | 206 (3.8) |  | 339 (6.2) | 206 (3.8) |  |
Sex | Â | Â | 0.000 | Â | Â | 0.730 |
 Female | 10,282 (52.3) | 2576 (47.2) |  | 2558 (46.9) | 2576 (47.2) |  |
 Male | 9370 (47.7) | 2882 (52.8) |  | 2900 (53.1) | 2882 (52.8) |  |
Marital status | Â | Â | 0.000 | Â | Â | 0.036 |
 Married | 10,325 (52.5) | 3361 (61.6) |  | 3467 (63.5) | 3361 (61.6) |  |
 Unmarrieda | 9327 (47.5) | 2097 (38.4) |  | 1991 (36.5) | 2097 (38.4) |  |
Race | Â | Â | 0.098 | Â | Â | 0.924 |
 White | 15,736 (80.1) | 4314 (79.0) |  | 4299 (78.8) | 4314 (79.0) |  |
 Black | 2114 (10.8) | 643 (11.8) |  | 647 (11.9) | 643 (11.8) |  |
 Other | 1802 (9.2) | 501 (9.2) |  | 512 (9.4) | 501 (9.2) |  |
Tumor site | Â | Â | 0.000 | Â | Â | 0.700 |
 Right colonb | 12,128 (61.7) | 2423 (44.4) |  | 2443 (44.8) | 2423 (44.4) |  |
 Left colonc | 7524 (38.3) | 3035 (55.6) |  | 3015 (55.2) | 3035 (55.6) |  |
Tumor size | Â | Â | 0.000 | Â | Â | 0.007 |
 <5 | 9649 (49.1) | 2302 (42.2) |  | 2441 (44.7) | 2302 (42.2) |  |
  ≥ 5 | 10,003 (50.9) | 3156 (57.8) |  | 3017 (55.3) | 3156 (57.8) |  |
Histology | Â | Â | 0.136 | Â | Â | 0.254 |
 Adenocarcinoma | 17,172 (87.4) | 4768 (87.4) |  | 4816 (88.2) | 4768 (87.4) |  |
 Mucinous adenocarcinoma | 2374 (12.1) | 648 (11.9) |  | 610 (11.2) | 648 (11.9) |  |
 Signet ring cell carcinoma | 106 (0.5) | 42 (0.8) |  | 32 (0.6) | 42 (0.8) |  |
Grade | Â | Â | 0.000 | Â | Â | 0.005 |
 I | 1311 (6.7) | 341 (6.2) |  | 282 (5.2) | 341 (6.2) |  |
 II | 15,192 (77.3) | 4050 (74.2) |  | 4196 (76.9) | 4050 (74.2) |  |
 III | 2818 (14.3) | 943 (17.3) |  | 853 (15.6) | 943 (17.3) |  |
 IV | 331 (1.7) | 124 (2.3) |  | 127 (2.3) | 124 (2.3) |  |
T stage | Â | Â | 0.000 | Â | Â | 0.000 |
 T3 | 17,663 (89.9) | 3919 (71.8) |  | 4279 (78.4) | 3919 (71.8) |  |
 T4 | 1989 (10.1) | 1539 (28.2) |  | 1179 (21.6) | 1539 (28.2) |  |
nLNd | Â | Â | 0.000 | Â | Â | 0.064 |
 0 | 92 (0.5) | 56 (1.0) |  | 35 (0.6) | 56 (1.0) |  |
 1–11 | 3507 (17.8) | 1056 (19.3) |  | 1093 (20.0) | 1056 (19.3) |  |
  ≥ 12 | 16,053 (81.7) | 4346 (79.6) |  | 4330 (79.3) | 4346 (79.6) |  |
CEAe | Â | Â | 0.000 | Â | Â | 0.026 |
 Positive | 7367 (37.5) | 2212 (40.5) |  | 2098 (38.4) | 2212 (40.5) |  |
 Negative | 12,285 (62.5) | 3246 (59.5) |  | 3360 (61.6) | 3246 (59.5) |  |