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Table 2 Comparison of categorical features for training (U.S.), first validation (Scandinavian) and second validation (Italian) datasets

From: How do we estimate survival? External validation of a tool for survival estimation in patients with metastatic bone disease—decision analysis and comparison of three international patient populations

Feature   Training set n = 189 Scandinavian set n = 815 Italian set n = 287
   No. % No. % % missing No. % % missing vs. training set p vs. Scandinavian set p
Gender male 85 45.0 369 45.3 0 120 42 0 0.50 0.31
female 104 55.0 446 54.7   167 58    
Oncologic diagnosis grouping 1.0 52 27.3 173 21.3 0.4 63 23 2 0.42 0.007*
2.0 34 18.2 74 9.2   44 16    
3.0 103 54.5 567 69.1   173 62    
Organ metastases yes 114 60.3 325 39.8 6.3 91 36 12 0.0001* 0.08
no 75 39.7 441 53.9   161 64    
Lymph node metastases yes 36 18.8 169 20.8 61.6 96 40 16 0.0001* 0.0007*
no 153 81.2 143 17.6   146 60    
Skeletal metastases solitary 55 29.0 123 15.2 3.4 139 49 1 0.0001* 0.0001*
multiple 134 71.0 666 81.4   144 51    
Pathologic fracture status yes 84 44.2 614 75 0.9 143 52 5 0.08 0.0001*
no 105 55.8 196 24.1   131 48    
ECOG performance status 0,1,2 93 49.2 558 68.3 0 123 54 20 0.39 0.0001*
3,4 96 50.8 257 31.7   106 46    
Survival >3 months yes 129 68.3 557 68.2 0 267 93 0 0.0001* 0.0001*
no 60 31.7 258 31.8   20 7    
Survival >12 months yes 79 41.8 241 29.8 0 181 63 0 0.0001* 0.0001*
no 110 58.2 574 70.2   106 37    
  1. Abbreviations: ECOG Eastern Cooperative Oncology Group, % missing, the proportion of unknown or missing data within the validation set
  2. *Proportions are significantly different between training and validation sets by Chi-square method