Table 2.
Clinical characteristics before and after propensity score matching
| Characteristics | Before matching (n=794) | Standardized differencea | P | After matching (n=398) | Standardized difference | P | ||
|---|---|---|---|---|---|---|---|---|
| SPPs (n=456) | APR (n=338) | SPPs (n=199) | APR (n=199) | |||||
| Age, median (range), y | 62 (21‐89) | 66 (31‐93) | 0.44 | <0.001 | 63 (21‐84) | 64 (31‐87) | −0.07 | 0.55 |
| Gender, n (%) | ||||||||
| Male | 307 (67) | 244 (72) | −0.11 | 0.14 | 149 (75) | 145 (73) | 0.05 | 0.73 |
| Female | 149 (33) | 93 (28) | 0.11 | 50 (25) | 54 (27) | −0.05 | ||
| BMI, n (%), kg/m2 | ||||||||
| <18.5 | 50 (11) | 49 (15) | −0.12 | 0.02 | 20 (10) | 21 (11) | −0.03 | 0.98 |
| 18.5‐25 | 321 (71) | 206 (61) | −0.21 | 132 (66) | 132 (66) | 0.00 | ||
| ≥25 | 84 (18) | 81 (24) | −0.15 | 47 (24) | 46 (23) | 0.02 | ||
| ASA‐PS, n (%) | ||||||||
| 1 | 194 (43) | 99 (29) | 0.29 | <0.001 | 73 (37) | 67 (34) | 0.06 | 0.75 |
| 2 | 250 (55) | 210 (63) | −0.16 | 119 (60) | 123 (62) | −0.04 | ||
| 3 | 9 (2) | 27 (8) | −0.28 | 7 (3) | 9 (5) | −0.10 | ||
| Comorbidity, n (%) | 221 (49) | 196 (58) | −0.18 | 0.01 | 102 (51) | 106 (53) | −0.04 | 0.76 |
| Diabetes mellitus | 59 (13) | 62 (18) | 30 (15) | 36 (18) | ||||
| Heart disease | 22 (5) | 23 (7) | 11 (6) | 13 (7) | ||||
| Cerebrovascular diseases | 11 (2) | 16 (5) | 3 (2) | 9 (5) | ||||
| Hypertension | 104 (23) | 84 (25) | 48 (24) | 45 (23) | ||||
| Others | 88 (19) | 95 (28) | 40 (20) | 51 (26) | ||||
| Clinical T stage, n (%) | ||||||||
| T3 | 406 (89) | 260 (77) | 0.32 | <0.001 | 165 (83) | 171 (86) | −0.08 | 0.58 |
| T4a | 21 (5) | 11 (3) | −0.10 | 11 (6) | 7 (4) | 0.09 | ||
| T4b | 29 (6) | 66 (20) | −0.43 | 23 (12) | 21 (11) | 0.03 | ||
| Clinical N stage, n (%) | ||||||||
| Negative | 295 (43) | 140 (42) | 0.02 | 0.72 | 81 (41) | 85 (43) | −0.04 | 0.76 |
| Positive | 360 (57) | 197 (58) | −0.02 | 118 (59) | 114 (57) | 0.04 | ||
| Clinical LLN involvement, n (%) | 53 (12) | 53 (16) | −0.12 | 0.11 | 28 (14) | 24 (12) | 0.06 | 0.66 |
| Distance from AV, median (range), cm | 4.0 (2.0‐5.0) | 3.0 (2.0‐5.0) | 0.91 | <0.001 | 4.0 (2.0‐5.0) | 4.0 (2.0‐5.0) | −0.03 | 0.77 |
| Stenosis, n (%) | 27 (6) | 26 (11) | −0.18 | 0.02 | 13 (7) | 16 (8) | −0.04 | 0.70 |
| Preoperative treatment, n (%) | 172 (38) | 99 (29) | 0.19 | 0.02 | 66 (33) | 67 (34) | −0.02 | >0.99 |
| Chemoradiation | 124 (27) | 73 (22) | 48 (24) | 52 (26) | ||||
| Chemotherapy | 37 (8) | 21 (6) | 17 (9) | 12 (6) | ||||
| Radiation | 11 (2) | 5 (1) | 1 (1) | 3 (2) | ||||
| Approach, n (%) | ||||||||
| Open | 270 (59) | 234 (69) | 0.21 | 0.005 | 131 (66) | 133 (67) | −0.02 | 0.92 |
| Laparoscopic | 186 (41) | 204 (31) | −0.21 | 68 (34) | 66 (33) | 0.02 | ||
| Hospital caseload, n (%) | ||||||||
| Low volume (<13/y) | 183 (40) | 191 (57) | −0.35 | <0.001 | 109 (55) | 100 (50) | 0.10 | 0.37 |
| High volume (≥13/y) | 273 (60) | 147 (43) | 0.35 | 90 (45) | 99 (50) | −0.10 | ||
| Procedure, n (%) | ||||||||
| LAR | 290 (64) | ‐ | ‐ | 111 (56) | ‐ | ‐ | ||
| ISR | 166 (36) | ‐ | 88 (44) | ‐ | ||||
a
Standardized difference is defined as the difference in means, scaled by the square root of the average of the two within‐group variances: , where , are group means, and are group variances.
ASA‐PS, American Society of Anesthesiologists Physical Status; AV, anal verge; BMI, body mass index; ISR, intersphincteric resection; LAR, low anterior resection; LLN, lateral pelvic lymph node.