Table 1 The equilibrium test of training set and testing set
Variable | Total (n = 365) | Group | Statistical magnitude | P | |
|---|---|---|---|---|---|
Training set (n = 255) | Testing set (n = 110) | ||||
Age receiving radiotherapy, Mean ± SD | 47.69 ± 11.01 | 47.97 ± 10.83 | 47.03 ± 11.44 | t = − 0.750 | 0.452 |
Gender, n (%) |  |  |  | χ2 = 0.089 | 0.765 |
 Female | 99 (27.12) | 68 (26.67) | 31 (28.18) |  |  |
 Male | 266 (72.88) | 187 (73.33) | 79 (71.82) |  |  |
History of drinking, n (%) |  |  |  | χ2 = 3.079 | 0.079 |
 No | 322 (88.22) | 220 (86.27) | 102 (92.73) |  |  |
 Yes | 43 (11.78) | 35 (13.73) | 8 (7.27) |  |  |
History of smoking, n (%) |  |  |  | χ2 = 4.120 | 0.042 |
 No | 273 (74.79) | 183 (71.76) | 90 (81.82) |  |  |
 Yes | 92 (25.21) | 72 (28.24) | 20 (18.18) |  |  |
History of surgery, n (%) |  |  |  | χ2 = 0.213 | 0.644 |
 No | 307 (84.11) | 213 (83.53) | 94 (85.45) |  |  |
 Yes | 58 (15.89) | 42 (16.47) | 16 (14.55) |  |  |
History of hypertension, n (%) |  |  |  | χ2 = 0.194 | 0.660 |
 No | 329 (90.14) | 231 (90.59) | 98 (89.09) |  |  |
 Yes | 36 (9.86) | 24 (9.41) | 12 (10.91) |  |  |
History of diabetes, n (%) |  |  |  | – | 1.000 |
 No | 359 (98.36) | 251 (98.43) | 108 (98.18) |  |  |
 Yes | 6 (1.64) | 4 (1.57) | 2 (1.82) |  |  |
T Stage, n (%) |  |  |  | χ2 = 1.056 | 0.788 |
 T1 | 75 (20.55) | 50 (19.61) | 25 (22.73) |  |  |
 T2 | 72 (19.73) | 53 (20.78) | 19 (17.27) |  |  |
 T3 | 163 (44.66) | 115 (45.10) | 48 (43.64) |  |  |
 T4 | 55 (15.07) | 37 (14.51) | 18 (16.36) |  |  |
N Stage, n (%) |  |  |  | χ2 = 2.391 | 0.495 |
 N0 | 35 (9.59) | 23 (9.02) | 12 (10.91) |  |  |
 N1 | 147 (40.27) | 105 (41.18) | 42 (38.18) |  |  |
 N2 | 153 (41.92) | 103 (40.39) | 50 (45.45) |  |  |
 N3 | 30 (8.22) | 24 (9.41) | 6 (5.45) |  |  |
Pathological type, n (%) |  |  |  | χ2 = 1.056 | 0.304 |
 A differentiated non-keratinic carcinoma | 24 (6.58) | 19 (7.45) | 5 (4.55) |  |  |
 An undifferentiated nonkeratinic carcinoma | 341 (93.42) | 236 (92.55) | 105 (95.45) |  |  |
Radiotherapy fraction, n (%) |  |  |  | χ2 = 0.731 | 0.393 |
 ≤ 30 | 237 (64.93) | 162 (63.53) | 75 (68.18) |  |  |
 > 30 | 128 (35.07) | 93 (36.47) | 35 (31.82) |  |  |
Dose at 50% of the left parotid volume (Gy), Mean ± SD | 25.45 ± 7.26 | 25.56 ± 7.21 | 25.21 ± 7.41 | t = − 0.41 | 0.681 |
Dose at 50% of the right parotid volume (Gy), Mean ± SD | 25.81 ± 7.72 | 26.15 ± 8.11 | 25.03 ± 6.69 | t = − 1.37 | 0.171 |
Mean dose to left parotid gland (Gy), Mean ± SD | 30.99 ± 5.66 | 31.13 ± 5.68 | 30.69 ± 5.65 | t = − 0.68 | 0.495 |
Mean dose to right parotid gland (Gy), Mean ± SD | 31.08 ± 6.08 | 31.38 ± 6.38 | 30.39 ± 5.26 | t = − 1.53 | 0.127 |
Mean dose to oral cavity mean dose (Gy), Mean ± SD | 32.65 ± 4.68 | 32.67 ± 4.71 | 32.59 ± 4.65 | t = − 0.150 | 0.880 |
Total radiotherapy dose (Gy), n (%) |  |  |  | χ2 = 0.452 | 0.501 |
 ≤ 70GY | 277 (75.89) | 191 (74.90) | 86 (78.18) |  |  |
 > 70GY | 88 (24.11) | 64 (25.10) | 24 (21.82) |  |  |
Mode of radiotherapy-NDP, n (%) |  |  |  | χ2 = 0.428 | 0.513 |
 No | 173 (47.40) | 118 (46.27) | 55 (50.00) |  |  |
 Yes | 192 (52.60) | 137 (53.73) | 55 (50.00) |  |  |
Mode of radiotherapy-DDP, n (%) |  |  |  | χ2 = 0.782 | 0.377 |
 No | 286 (78.36) | 203 (79.61) | 83 (75.45) |  |  |
 Yes | 79 (21.64) | 52 (20.39) | 27 (24.55) |  |  |
Mode of radiotherapy-Others, n (%) |  |  |  | χ2 = 0.000 | 0.989 |
 No | 345 (94.52) | 241 (94.51) | 104 (94.55) |  |  |
 Yes | 20 (5.48) | 14 (5.49) | 6 (5.45) |  |  |
Course of induction chemotherapy, M (Q1, Q3) | 2.00 (2.00, 3.00) | 2.00 (2.00, 3.00) | 2.00 (2.00, 3.00) | Z = 0.040 | 0.968 |
Concomitant chemoradiotherapy, n (%) |  |  |  | χ2 = 0.049 | 0.824 |
 No | 77 (21.10) | 53 (20.78) | 24 (21.82) |  |  |
 Yes | 288 (78.90) | 202 (79.22) | 86 (78.18) |  |  |
Induction chemotherapy, n (%) |  |  |  | χ2 = 0.000 | 0.986 |
 No | 30 (8.22) | 21 (8.24) | 9 (8.18) |  |  |
 Yes | 335 (91.78) | 234 (91.76) | 101 (91.82) |  |  |
The regimens of induction chemotherapy, n (%) |  |  |  | χ2 = 2.252 | 0.895 |
 DP | 111 (30.41) | 79 (30.98) | 32 (29.09) |  |  |
 DPF | 55 (15.07) | 35 (13.73) | 20 (18.18) |  |  |
 GP | 59 (16.16) | 43 (16.86) | 16 (14.55) |  |  |
 None | 30 (8.22) | 21 (8.24) | 9 (8.18) |  |  |
 Others | 4 (1.10) | 2 (0.78) | 2 (1.82) |  |  |
 TP | 65 (17.81) | 47 (18.43) | 18 (16.36) |  |  |
 TPF | 41 (11.23) | 28 (10.98) | 13 (11.82) |  |  |
Xerostomia, n (%) |  |  |  | χ2 = 1.990 | 0.574 |
 Grade 0 | 84 (23.01) | 63 (24.71) | 21 (19.09) |  |  |
 Grade 1 | 142 (38.90) | 94 (36.86) | 48 (43.64) |  |  |
 Grade 2 | 108 (29.59) | 76 (29.80) | 32 (29.09) |  |  |
 Grade 3 | 31 (8.49) | 22 (8.63) | 9 (8.18) |  |  |