Table 6.

Odds ratio and 95% CI for the association between clinical and pathological characteristics of breast cancer with categories of Ki67 (≤10% vs. >10%) among 9,059 patients

Characteristic	Cases (N)	OR* (95% CI)	p‐value
Age at diagnosis
<35	328	1.00 (Referent)
35–50	3,043	0.64 (0.50–0.83)	1.00E‐03
>50–65	4,064	0.55 (0.43–0.72)	4.79E‐06
>65	1,414	0.60 (0.45–0.80)	2.43E‐04
Tumour grade
Low grade	1,696	1.00 (Referent)
Intermediate grade	3,684	1.69 (1.45–1.97)	4.71E‐12
High grade	2,552	4.18 (3.57–4.89)	3.57E‐72
Stage
I	3,214	1.00 (Referent)
II	3,534	1.15 (1.03–1.27)	1.00E‐02
III	473	1.41 (1.13–1.28)	2.00E‐03
IV	97	1.77 (1.15–2.72)	9.00E‐03
Morphology
Ductal	4,315	1.00 (Referent)
Lobular	860	0.36 (0.29–0.43)	1.98E‐25
Other	648	0.68 (0.56–0.82)	4.62E‐05
Tumour size
<2 cm	4,492	1.00 (Referent)
2–4.9 cm	2,565	1.31 (1.17–1.46)	6.64E‐07
>5 cm	244	1.29 (0.96–1.72)	8.60E‐02
Node status
Negative	4,758	1.00 (Referent)
Positive	3,168	1.11 (1.00–1.23)	4.00E‐02
ER expression
Negative	2,222	1.00 (Referent)
Positive	6,128	0.42 (0.38–0.47)	1.09E‐55
PR expression
Negative	2,853	1.00 (Referent)
Positive	4,919	0.51 (0.46–0.56)	1.68E‐36
HER2 expression
Negative	5,379	1.00 (Referent)
Positive	1,060	1.61 (1.40–1.85)	1.30E‐11
EGFR expression
Negative	2,407	1.00 (Referent)
Positive	356	3.08 (2.40–3.95)	4.61E‐19
CK5/6 expression
Negative	4,184	1.00 (Referent)
Positive	623	1.73 (1.45–2.07)	5.69E‐10

All variables were modelled separately and each model was adjusted for age at diagnosis and study group. Other morphology includes all other histological subtypes of breast cancer that are neither invasive ductal (NOS) nor invasive lobular.

*OR refers to the odds of each clinico‐pathological characteristic being high Ki67 expressing