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. 2015 Feb 6;107(3):dju491. doi: 10.1093/jnci/dju491

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.