Table 1.
Distribution of select patient- and hospital-level variables for stage I-III colon cancer patients by surgical procedures (LC vs OC) before and after PS matching*
| Select variables | Unmatched | PS Matched | ||||
|---|---|---|---|---|---|---|
| LC | OC | P† | LC | OC | P | |
| n = 18 717 | n = 27 159 | n = 18 230 | n = 18 230 | |||
| No. (Col %) | No. (Col %) | No. (Col %) | No. (Col %) | |||
| Primary site‡ | ||||||
| Right colon | 10 049 (53.69) | 13 830 (50.92) | <.001 | 9756 (53.52) | 9860 (54.09) | .37 |
| Transverse colon | 2319 (12.39) | 3786 (13.94) | 2283 (12.52) | 2306 (12.65) | ||
| Left colon | 6349 (33.92) | 9543 (35.14) | 6191 (33.96) | 6064 (33.26) | ||
| Tumor grade | ||||||
| Well to moderately differentiated | 15 067 (80.50) | 21 536 (79.30) | <.001 | 14 663 (80.43) | 14 569 (79.92) | .26 |
| Poorly to undifferentiated | 3050 (16.30) | 4852 (17.87) | 2999 (16.45) | 3044 (16.70) | ||
| Missing | 600 (3.21) | 771 (2.84) | 568 (3.12) | 617 (3.38) | ||
| Positive surgical margin | ||||||
| No | 18 034 (96.35) | 25 558 (94.11) | <.001 | 17 554 (96.29) | 17 564 (96.35) | .96 |
| Yes | 628 (3.36) | 1493 (5.50) | 621 (3.41) | 612 (3.36) | ||
| Missing | 55 (0.29) | 108 (0.40) | 55 (0.30) | 54 (0.30) | ||
| Lymphovascular invasion | ||||||
| No | 13 165 (70.34) | 18 321 (67.46) | <.001 | 12 786 (70.14) | 12 741 (69.89) | .85 |
| Yes | 4046 (21.62) | 6380 (23.49) | 3972 (21.79) | 3994 (21.91) | ||
| Missing | 1506 (8.05) | 2458 (9.05) | 1472 (8.07) | 1495 (8.20) | ||
| Surgery of the primary site | ||||||
| Partial colectomy | 6935 (37.05) | 9414 (34.66) | <.001 | 6705 (36.78) | 6552 (35.94) | .23 |
| Subtotal/total colectomy | 11 720 (62.62) | 17 616 (64.86) | 11 463 (62.88) | 11 610 (63.69) | ||
| Total proctocolectomy | 62 (0.33) | 129 (0.47) | 62 (0.34) | 68 (0.37) | ||
| Tumor size | ||||||
| Lowest quartile (<30mm) | 5359 (28.63) | 5769 (21.24) | <.001 | 5084 (27.89) | 5082 (27.88) | .81 |
| Second quartile (30mm to 41mm) | 4572 (24.43) | 6474 (23.84) | 4507 (24.72) | 4428 (24.29) | ||
| Third quartile (42mm to 59mm) | 4089 (21.85) | 6422 (23.65) | 4045 (22.19) | 4035 (22.13) | ||
| Highest quartile (≥60mm) | 3646 (19.48) | 7379 (27.17) | 3625 (19.88) | 3695 (20.27) | ||
| Missing | 1051 (5.62) | 1115 (4.11) | 969 (5.32) | 990 (5.43) | ||
| Stage | ||||||
| Stage 1 | 6097 (32.57) | 6476 (23.84) | <.001 | 5731 (31.44) | 5710 (31.32) | .81 |
| Stage 2 | 6170 (32.96) | 10 154 (37.39) | 6104 (33.48) | 6066 (33.27) | ||
| Stage 3 | 6450 (34.46) | 10 529 (38.77) | 6395 (35.08) | 6454 (35.40) | ||
| Charlson Comorbidity Index | ||||||
| 0 | 12 574 (67.18) | 18 295 (67.36) | .005 | 12 245 (67.17) | 12 151 (66.65) | .57 |
| 1 | 4513 (24.11) | 6297 (23.19) | 4379 (24.02) | 4454 (24.43) | ||
| 2 or above | 1630 (8.71) | 2567 (9.45) | 1606 (8.81) | 1625 (8.91) | ||
| Age groups | ||||||
| 18 to 49 y | 1888 (10.09) | 2734 (10.07) | <.001 | 1833 (10.05) | 1749 (9.59) | .40 |
| 50 to 64 y | 6154 (32.88) | 8403 (30.94) | 5909 (32.41) | 5869 (32.19) | ||
| 65 to 74 y | 5512 (29.45) | 7914 (29.14) | 5400 (29.62) | 5486 (30.09) | ||
| 75 to 84 y | 5163 (27.58) | 8108 (29.85) | 5088 (27.91) | 5126 (28.12) | ||
| Race/ethnicity | ||||||
| Non-Hispanic White | 14 061 (75.12) | 19 374 (71.34) | <.001 | 13 651 (74.88) | 13 669 (74.98) | .62 |
| Hispanic | 868 (4.64) | 1454 (5.35) | 852 (4.67) | 802 (4.40) | ||
| Black | 2135 (11.41) | 3832 (14.11) | 2103 (11.54) | 2145 (11.77) | ||
| Asian & PI | 553 (2.95) | 817 (3.01) | 546 (3.00) | 565 (3.10) | ||
| Other | 1100 (5.88) | 1682 (6.19) | 1078 (5.91) | 1049 (5.75) | ||
| Female | ||||||
| No | 9333 (49.86) | 13 550 (49.89) | .95 | 9074 (49.78) | 9113 (49.99) | .68 |
| Yes | 9384 (50.14) | 13 609 (50.11) | 9156 (50.22) | 9117 (50.01) | ||
| Primary payer (insurance type) | ||||||
| Missing | 156 (0.83) | 465 (1.71) | <.001 | 153 (0.84) | 166 (0.91) | .87 |
| Uninsured | 466 (2.49) | 1290 (4.75) | 458 (2.51) | 464 (2.55) | ||
| Medicaid | 721 (3.85) | 1502 (5.53) | 716 (3.93) | 689 (3.78) | ||
| Younger Medicare | 716 (3.83) | 1246 (4.59) | 710 (3.89) | 717 (3.93) | ||
| Older Medicare | 8996 (48.06) | 13 291 (48.94) | 8836 (48.47) | 8912 (48.89) | ||
| Private | 7662 (40.94) | 9365 (34.48) | 7357 (40.36) | 7282 (39.95) | ||
| Facility type | ||||||
| Community cancer program | 2169 (11.59) | 4821 (17.75) | <.001 | 2157 (11.83) | 2175 (11.93) | .82 |
| Comprehensive community cancer program | 9827 (52.50) | 13 837 (50.95) | 9680 (53.10) | 9685 (53.13) | ||
| Teaching/research center | 3701 (19.77) | 5246 (19.32) | 3608 (19.79) | 3557 (19.51) | ||
| NCI-designated cancer center | 1081 (5.78) | 962 (3.54) | 923 (5.06) | 898 (4.93) | ||
| Other | 1939 (10.36) | 2293 (8.44) | 1862 (10.21) | 1915 (10.50) | ||
| Volume measurement§ | ||||||
| Low-volume surgeon low-volume hospital | 7868 (42.04) | 14 744 (54.29) | <.001 | 7832 (42.97) | 7802 (42.80) | .53 |
| High-volume surgeon low-volume hospital | 4476 (23.91) | 4636 (17.07) | 4285 (23.50) | 4397 (24.12) | ||
| Low-volume surgeon high-volume hospital | 2845 (15.20) | 4517 (16.63) | 2833 (15.54) | 2815 (15.44) | ||
| High-volume surgeon high- volume hospital | 3528 (18.85) | 3262 (12.01) | 3280 (17.99) | 3216 (17.64) | ||
* All statistical tests were two-sided. LC = laparoscopic colectomy; NCI = National Cancer Institute; OC = open colectomy; PI = Pacific Islander; PS = propensity score.
† P value calculated using Pearson’s chi-squared test.
‡ Right colon includes cecum, ascending colon, and hepatic flexure of colon, transverse colon includes transverse colon and splenic flexure of colon, and left colon includes descending colon and sigmoid colon.
§ High-volume surgeon is defined as more than six colectomies within a particular year; high-volume hospital is defined as more than 36 colectomies within a particular year, both of which are the top 10th percentiles.