Table 1. Demographic and Clinical Characteristics of the Development and Validation Cohortsa.
| Characteristic | Total (N = 8403) | Development cohort (n = 4172) | Validation cohort (n = 4231) | P valueb |
|---|---|---|---|---|
| Sex | ||||
| Male | 6641 (79.0) | 3288 (78.8) | 3353 (79.2) | .62 |
| Female | 1762 (21.0) | 884 (21.2) | 878 (20.8) | |
| Age, mean (SD), y | 63.6 (9.0) | 63.8 (9.0) | 63.4 (10.0) | .73 |
| Age group, y | ||||
| ≤40 | 170 (2.0) | 75 (1.8) | 95 (2.2) | .24 |
| 41-50 | 658 (7.8) | 321 (7.7) | 337 (8.0) | |
| 51-60 | 2076 (24.7) | 1038 (24.9) | 1038 (24.5) | |
| 61-70 | 3357 (40.0) | 1641 (39.3) | 1716 (40.6) | |
| 71-80 | 1920 (22.8) | 975 (23.4) | 945 (22.3) | |
| >80 | 222 (2.5) | 122 (2.9) | 100 (2.4) | |
| BMI, mean (SD) | 26.04 (5.0) | 26.07 (5.0) | 26.0 (5.0) | .57 |
| BMI group | ||||
| <18.5 | 445 (5.3) | 227 (5.4) | 218 (5.2) | .90 |
| 18.5-24.9 | 3386 (40.3) | 1668 (40.0) | 1718 (40.6) | |
| 25-29.9 | 2966 (35.3) | 1478 (35.4) | 1488 (35.2) | |
| ≥30 | 1606 (19.1) | 799 (19.2) | 807 (19.1) | |
| WHO/ECOG performance status | ||||
| 0 | 4205 (50.0) | 2073 (49.7) | 2132 (50.4) | .85 |
| 1 | 3753 (44.7) | 1878 (45.0) | 1875 (44.3) | |
| 2 | 379 (4.5) | 186 (4.5) | 193 (4.6) | |
| 3 | 66 (0.8) | 35 (0.8) | 31 (0.7) | |
| Myocardial infarction | 442 (5.3) | 215 (5.2) | 227 (5.4) | .66 |
| Connective tissue disease | 71 (0.8) | 36 (0.9) | 35 (0.8) | .85 |
| Chronic pulmonary disease | 845 (10.1) | 417 (10.0) | 428 (10.1) | .85 |
| Moderate to severe renal disease | 136 (1.6) | 66 (1.6) | 70 (1.7) | .79 |
| Peripheral vascular disease | 433 (5.2) | 220 (5.3) | 213 (5.0) | .62 |
| Diabetes (uncomplicated) | 1058 (12.6) | 550 (13.2) | 508 (12.0) | .10 |
| Diabetes (end-organ damage) | 62 (0.7) | 33 (0.8) | 29 (.7) | .57 |
| Liver disease (mild) | 167 (2.0) | 84 (2.0) | 83 (2.0) | .86 |
| Liver disease (moderate to severe) | 35 (0.4) | 20 (0.5) | 15 (0.4) | .37 |
| Solid tumor present | 8228 (97.9) | 4086 (97.9) | 4142 (97.9) | .89 |
| Neoadjuvant therapy | ||||
| Chemoradiotherapy | 3916 (46.6) | 1969 (47.2) | 1947 (46.0) | .49 |
| Chemotherapy | 2393 (28.5) | 1199 (28.7) | 1194 (28.2) | |
| Definitive chemoradiotherapy | 154 (1.7) | 76 (1.8) | 78 (1.8) | |
| Radiotherapy alone | 13 (0.1) | 6 (0.1) | 7 (0.1) | |
| None | 1927 (23.0) | 922 (22.0) | 1005 (23.8) | |
| Volume activity, mean per year per center | ||||
| 0-45.9 | 2169 (25.8) | 1102 (26.4) | 1067 (25.2) | .40 |
| 46-71.6 | 1975 (23.5) | 980 (23.5) | 995 (23.5) | |
| 71.7-108.6 | 2355 (28.0) | 1138 (27.3) | 1217 (28.8) | |
| >108.6 | 1904 (22.7) | 952 (22.8) | 952 (22.5) | |
| Deaths within 30 postoperative days | 164 (2.0) | 89 (2.1) | 75 (1.8) | .23 |
| Grade V (Clavien-Dindo) | 196 (2.3) | 100 (2.3) | 96 (2.4) | .69 |
| Deaths within 90 postoperative days | 353 (4.2) | 184 (4.4) | 169 (4.0) | |
| In-hospital before discharge | 191/353 (54.1) | 100/184 (54.3) | 91/169 (53.8) | .34 |
| No readmission within 30 d of discharge | 116/353 (32.9) | 59/184 (32.1) | 57/169 (33.7) | |
| Readmission related within 30 d of discharge | 34/353 (9.6) | 18/184 (9.7) | 16/169 (9.4) | |
| Readmission status within 30 d not known | 6/353 (1.7) | 3/184 (1.6) | 3/169 (1.7) | |
| Unrelated readmission within 30 d of discharge | 6/353 (1.7) | 4/184 (2.1) | 2/169 (1.1) |
Abbreviation: BMI, body mass index (calculated as weight in kilograms divided by height in meters squared).
a
Data are presented as number/total number (percentage) of patients unless otherwise indicated.
b
Fisher exact test and χ2 test were used as appropriate.