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

Table 7 Coefficients, hazard ratios (95% CI), and P-values from the prognostic model

Prognostic factor	Coefficient	HR	95% CI	p-value
Histological grade
I	0	1
II	1.33	3.78	1.74 to 8.20	< 0.001
III	2.66	14.29	3.03 to 67.24	< 0.001
N status
0	0	1
1	0.97	2.64	1.87 to 3.73	< 0.001
2	1.94	6.96	3.50 to 13.91	< 0.001
3	2.91	18.36	6.54 to 51.90	< 0.001
Ki67 status^a
Low	0.00	1.00
High	1.65	5.21	2.31 to 11.74	< 0.001
PR status^b
Low	0.00	1.00
High	−1.80	0.17	0.05 to 0.55	0.003
Age^c
Young	0.00	1.00
Middle aged	−1.56	0.21	0.05 to 0.83	0.025
Elderly	−0.18	0.83	0.25 to 2.72	0.761
PR-age after 164 weeks^d
0	0.00	1.00
1	1.59	4.92	1.04 to 23.33	0.045

HR hazard ratio, CI confidence interval
^aRegarding Ki67 status, the patients were divided into two groups: low (Ki67 < 60%) and high (Ki67 ≥ 60%)
^bRegarding PR status, the patients were divided into two groups: low (PR < 20%) and high (PR ≥ 20%)
^cRegarding age, the patients were divided into three groups: young (< 41 years old), middle aged (41–55 years old), and elderly (55 and older)
^dPR-age after 164 weeks (age ≥ 41 years, PR ≥ 20%), a binary variable, an interaction item between age and PR status after 164 weeks after surgery, which is one if age is no less than 41 years old and PR is no less than 20% and zero otherwise

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