Fig. 4

Variability in 21-gene experimental recurrence scores and 21-gene group scores between paired breast cancer samples. a Difference in 21-gene experimental recurrence scores (RS) between paired breast cancer samples by age. Recurrence scores were calculated from reference-normalised gene expression as described in the “Methods” section, and discordances were quantified by calculating the absolute difference in recurrence score between sample 1 and sample 2. Linear regressions were performed to investigate the association between the difference in recurrence score and age as a continuous variable. Data are presented as individual values. b–e Discordance in 21-gene group scores between paired breast cancer samples collected from younger women. For women aged < 50 years old, an arbitrary threshold of 4 units was set to distinguish between paired samples showing small differences in recurrence scores of ≤ 4 units (n = 9) and paired samples showing large differences in recurrence scores of > 4 units (n = 7). The 21-gene group scores were calculated for each tumour, as described in the “Methods” section, and changes in group scores between paired breast cancer samples were compared. The change in the b Proliferation group, c Oestrogen group, d HER2 group and e Invasion group scores between paired breast cancer samples. Results are presented as mean + SEM. Mean discordances were compared using the independent t test. Statistical significance was determined when p ≤ 0.05; an asterisk signifies p ≤ 0.05