Table 1. Clinical and tumor characteristics of enrolled patients.
| Variables | Before PS matching | After PS matching | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| MRI (-) (n = 165) | MRI (+) (n = 105) | P | SMD | MRI (-) (n = 65) | MRI (+) (n = 65) | P | SMD | |||
| Age, yr | 51.4 ± 13.9 | 47.4 ± 13.4 | 0.034* | -0.26 | 49.0 ± 14.5 | 46.9 ± 15.3 | 0.429* | -0.13 | ||
| Sex | ||||||||||
| Male | 89 (53.9) | 35 (33.3) | 0.001 | -0.44 | 25 (38.5) | 27 (41.5) | 0.858 | 0.07 | ||
| Female | 76 (46.1) | 70 (66.7) | 40 (61.5) | 38 (58.5) | ||||||
| Surgical factors | ||||||||||
| Surgeons | ||||||||||
| Surgeon #1 | 99 (60.0) | 93 (88.6) | < 0.001 | 0.9 | 56 (86.2) | 55 (84.6) | > 0.999 | -0.05 | ||
| Surgeon #2–3 | 66 (40.0) | 12 (11.4) | 9 (13.8) | 10 (15.4) | ||||||
| Revision surgery | ||||||||||
| Yes | 5 (3.0) | 3 (2.9) | > 0.999† | -0.01 | 3 (4.6) | 2 (3.1) | > 0.999† | -0.09 | ||
| Tumor factors | ||||||||||
| Size, median (IQR), cm | 2.7 (2.3 to 3.5) | 3.5 (2.9 to 4.0) | < 0.001‡ | 0.43 | 3.0 (2.3 to 4.0) | 3.1 (2.7 to 3.6) | 0.212‡ | 0.07 | ||
| Multiplicity | ||||||||||
| Yes | 7 (4.2) | 5 (4.8) | > 0.999† | 0.02 | 4 (6.2) | 2 (3.1) | 0.680† | -0.14 | ||
| Tumor location | ||||||||||
| Superficial lobe | 133 (80.6) | 54 (51.4) | < 0.001 | -0.59 | 42 (64.6) | 42 (64.6) | 1.000 | < 0.01 | ||
| Deep or both lobe | 32 (19.4) | 51 (48.6) | 23 (35.4) | 23 (35.4) | ||||||
| Pathology | ||||||||||
| Benign | 144 (87.3) | 77 (73.3) | 0.006 | 0.32 | 51 (78.5) | 55 (84.6) | 0.498 | -0.14 | ||
| Malignancy | 21 (12.7) | 28 (26.7) | 14 (21.5) | 10 (15.4) | ||||||
Values are presented as mean ± standard deviation or n (%) unless otherwise indicated. Surgeon factor: Surgeon #1: parotid surgery > 100/year, surgical experience in the head and neck field = 20 years, Surgeon #2: parotid surgery = 20-30/year, surgical experience in the head and neck field = 25 years, Surgeon #3: parotid surgery = 20-30/year, surgical experience in the head and neck field = 15 years. Temporary FNP: < 6 months after parotidectomy, Permanent FNP: persistent FNP at 6-18 months after parotidectomy. Operation time: See Supplementary Fig. 1. Statistical tests without symbols used Pearson’s Chi-squared test.
*Student T-test, †Fisher’s exact test for count data, ‡Wilcoxon’s rank-sum test.
PS = propensity score, MRI = magnetic resonance imaging, SMD = standardized mean difference, IQR = interquartile range, FNP = facial nerve palsy