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Table 3 Breast tumour size, percentage of positive lymph nodes and outcome–stratification by tumour type*
% of Lymph nodes positive
Relative risk (95% CI)
Hazard ratio (95% CI)
Luminal A (n = 1005)
≤1.5 cm
0.08
1.00
1.00
>1.5–2 cm
0.16
1.66 (1.25–2.19)
2.08 (1.36–3.17)
>2 cm
0.27
2.87 (2.25–3.65)
2.68 (1.79–4.01)
P trend
<0.001
<0.001
Luminal B (n = 66)
≤1.5 cm
0.08
1.00
1.00
>1.5–2 cm
0.09
1.61 (0.49–5.31)
0.74 (0.23–2.32)
>2 cm
0.38
5.46 (2.03–14.6)
1.98 (0.82–4.78)
P trend
<0.001
0.08
ER-/HER2 + (n = 107)
≤1.5 cm
0.16
1.00
1.00
>1.5–2 cm
0.18
0.91 (0.42–1.97)
1.17 (0.45–3.02)
>2 cm
0.34
2.09 (1.23–3.57)
2.24 (0.99–5.07)
P trend
0.002
0.04
ER-/HER2–non-basal (n = 109)
≤1.5 cm
0.04
1.00
1.00
>1.5–2 cm
0.12
3.94 (1.32–11.7)
2.73 (0.77–9.69)
>2 cm
0.25
6.64 (2.49–17.7)
3.26 (1.10–9.64)
P trend
<0.001
0.03
Basal (n = 196)
≤1.5 cm
0.12
1.00
1.00
>1.5–2 cm
0.14
1.40 (0.73–2.68)
1.27 (0.61–2.61)
>2 cm
0.17
1.30 (0.70–2.40)
1.34 (0.68–2.66)
P trend
0.58
0.43
P for interaction**
0.005
0.51
* 37 patients who had missing data for ER and HER2 but whose tumours were definitely non-basal were not included in the above analysis. The relative risk was modelled via Poisson regression and the outcome was modelled via Cox Regression. All results are adjusted for grade. ** The P for interaction is obtained from fitting size as a categorical covariate (≤1.5 cm, >1.5–2 cm, ≥2 cm) and testing whether the effect of size on outcome differs according to tumour subgroup, when size is fitted as a continuous covariate the P-values for the interaction term are 0.002 for the relative risk and 0.48 for the hazard ratio. For the purposes of this analysis, we defined Luminal A as ER+ , HER2− and Luminal B as ER+, HER2+. ER−, HER2− non-basal cases are triple negative patients that are also negative for CK5/6, CK14 and EGFR. Basal is defined as described in the text
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