Development and validation of an extended Cox prognostic model for patients with ER/PR+ and HER2− breast cancer: a retrospective cohort study

Table 5 Prognostic factors, coefficients, hazard ratios, and P-values of the Z-tests in model 2

Variable	Prognostic factor	Coefficient	HR (95% CI)	p-value
x₁	Histological grade (I, II, III)	1.392	4.024 (1.865, 8.684)	< 0.001
x₂	N status (0, 1, 2, 3)	0.995	2.706 (1.929, 3.795)	< 0.001
x₃	Ki67 status (60%)	1.595	4.930 (2.181, 11.143)	< 0.001
x₅	Age (55 years)	1.202	3.325 (1.496, 7.389)	0.003
x₆	PR − age (Age ≥ 41 years, PR ≥ 20%)	−1.157	0.315 (0.148, 0.669)	0.003

HR hazard ratio, CI confidence interval. Ki67 status (60%), a binary variable that is one if Ki67 is no less than 60% and zero otherwise. Age (55 years), a binary variable that is one if age is no less than 55 years and zero otherwise. PR − age (age ≥ 41 years, PR ≥ 20%), a binary variable, an interaction item between age and PR, which is one if age is no less than 41 years and PR is no less than 20% and zero otherwise

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