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Table 1 The equilibrium test of training set and testing set

From: A prediction model for xerostomia in locoregionally advanced nasopharyngeal carcinoma patients receiving radical radiotherapy

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)   
  1. PFS progression-free survival, NDP Nedaplatin, DDP cisplatin, DPF docetaxel + cisplatin + 5-fluorouracil, TPF docetaxel + cisplatin + 5-fluorouracil, DP cisplatin + docetaxel, TP cisplatin, GP gemcitabine + cisplatin, SD standard deviation