BACKGROUND: Breast cancer patients with node positive disease can have an 
excellent outcome with tamoxifen only. It is unclear whether analysing both the 
70-gene signature and hormone receptors provides superior prediction of outcome 
in tamoxifen-treated patients than either alone.
METHODS: Three series were evaluated: 121 patients (81% node positive) received 
adjuvant tamoxifen, 151 patients did not receive tamoxifen (10% node positive) 
and 92 patients received tamoxifen for metastatic disease. The 70-gene signature 
was analysed using MammaPrint. Oestrogen receptor (ER) and progesterone receptor 
(PR) immunohistochemistry was evaluated following St. Gallen Consensus (Highly 
Endocrine Responsive: ER and PR ≥ 50%, Incompletely Endocrine Responsive: ER 
and/or PR low or either one absent).
RESULTS: In patients treated with adjuvant tamoxifen, both the 70-gene signature 
(adjusted for Endocrine Response Categories HR 2.17, 95%CI 1.01-4.66) as well as 
the Endocrine Response Categories (adjusted for 70-gene signature HR 6.35, 95%CI 
1.90-21.3) were associated with breast-cancer-specific-survival (BCSS). Also in 
patients treated with tamoxifen for metastatic disease, combined analysis of the 
70-gene signature and ER/PR revealed additional value (multivariate Cox 
regression, p = 0.013). In patients who did not receive tamoxifen, only the 
70-gene signature was associated with outcome.
CONCLUSION: In the series analysed, the 70-gene signature was mainly a 
prognostic factor, while ER and PR levels were mainly associated with outcome 
after tamoxifen. Combination of these three factors may improve outcome 
prediction in tamoxifen-treated patients.