ERBB2 and breast cancer: Importantly, the high agreement was also mirrored on a group level by similar prognostic performance for SSP and NCN models when assessed in the independent test data (Fig. 4), particularly within the relevant clinical subgroup of post-menopausal (>50 years) ER+/HER2-/N0 BC treated with endocrine treatment alone (Fig. 4c–g).