Table 5 

Choice of the Cox regression model (N = 196) 

Stepwise inclusion of variable 
2 × increase in partial loglikelihood (χ^{2 }distributed) 
df 
P 


Stage 
23.43 
3 
< 0.0001 
Estrogen receptor 
7.92 
1 
0.005 
cerbB2 
7.34 
1 
0.01 
Topoisomerase IIα 
9.85 
1 
0.002 
Grading 
0.01 
1 
0.92 
Topoisomerase IIα × grading 
4.64 
1 
0.03 
cerbB2 × grading 
1.74 
1 
0.19 
cerbB2 × topoisomerase IIα 
0.17 
1 
0.68 


Starting from the null model, successive adding of the variables mentioned above improves the Cox proportional hazard model in the first four steps significantly. In this sense the first four variables can be considered as independent prognostic factors. df, degrees of freedom. 

Fritz et al. Breast Cancer Research 2005 7:R374R384 doi:10.1186/bcr1012 