Supplementary Table 1: Interobserver agreement for p53 expression
Normal Loss of
P53 expression expression Overexpression expression Ƙ value Normal expression 10 (7%) 3 (2%) 3 (2%) 0.79 Overexpression 5 (3%) 85 (58%) 0 (0%) Loss of expression 6 (4%) 0 (0%) 35 (24%)
Cohen ƙ statistics were used to determine interobserver agreement.
Supplementary Table 2: Interobserver agreement for SOX2 expression
Positive Absence of
SOX2 expression expression expression ƙ value Positive expression 46 (31%) 7 (5%) 0.73 Absence of expression 12 (8%) 82 (56%)
Cohen ƙ statistics were used to determine interobserver agreement.
Supplementary Table 3: Correlation between biomarker expression and clinicopathologic characteristics of all 147 patients
Total cohort of 147 patients
Normal P53 Aberrant P53c SOX2 positive Absence of SOX2
Variable n = 22 n = 125 P Value n = 60 n = 87 P Value
Age
Median, years (IQR) 63 (57 ‐ 70) 64 (57 ‐ 70) 0.957 62 (55 ‐ 66) 64 (58 ‐ 71) 0.050
Gender
Woman 5 (23%) 13 (10%) 0.150 4 (7%) 14 (16%) 0.087
Men 17 (77%) 112 (90%) 56 (93%) 73 (84%)
Tumor grade
Well and moderately‐diff 15 (68%) 78 (62%) 0.604 30 (50%) 63 (72%) 0.006
Poorly‐diff 7 (32%) 47 (38%) 30 (50%) 24 (28%)
Median time between nCRT
and surgery, days (IQR) 51 (46‐61) 50 (39‐67) 0.820 50 (36‐62) 52 (41‐71) 0.114
cT‐stagea
cT1 0 (0%) 5 (4%) 0.431 1 (2%) 4 (5%) 0.273
cT2 6 (27%) 23 (18%) 9 (15%) 20 (23%)
cT3 16 (73%) 97 (78%) 50 (83%) 63 (72%)
cN‐stagea
cN0 9 (41%) 37 (30%) 0.478 20 (33%) 26 (30%) 0.478
cN1 6 (27%) 49 (39%) 19 (32%) 36 (41%)
cN2/3 7 (32%) 39 (31%) 21 (35%) 25 (29%)
PrepT‐stageb
prepT1/T2 2 (9%) 19 (15%) 0.443 6 (10%) 15 (17%) 0.232
prepT3 20 (91%) 105 (85%) 53 (90%) 72 (83%)
prepN‐stageb
prepN0 7 (32%) 55 (44%) 0.548 21 (36%) 41 (47%) 0.236
prepN1 11 (50%) 51 (41%) 30 (51%) 32 (37%)
prepN2/N3 4 (18%) 18 (15%) 8 (13%) 14 (16%)
Kruskall‐Wallis test and Pearson chi‐square test or Fisher exact test were used to compare the characteristics of different biomarker expression.
a Pretreatment T and N‐stages as defined by endoscopic ultrasonography
b Preoperative T and N‐stage estimated based on the extent of regressional changes (eg, fibrosis, keratin pearls, mucous lakes and/or foreign body cell reactions) and on the residual tumor cells in the resection specimen.
c Aberrant p53 expression was defined as either overexpression or complete loss of expression Abbreviation: IQR, interquartile range