Epidermal growth factor receptor (EGFR) and the estrogen receptor modulator amplified in breast cancer (AIB1) for predicting clinical outcome after adjuvant tamoxifen in breast cancer

The epidermal growth factor receptor (EGFR) and the estrogen receptor (ER) modulator Amplified In Breast cancer-1 (AIB1) have been reported to be of importance for the prognosis of breast cancer patients. We have analyzed AIB1 and EGFR by immunohistochemistry in primary breast cancers (n = 297) arranged in a tissue microarray in order to predict outcome after adjuvant endocrine therapy with tamoxifen for two years. High expression of AIB1 was associated with DNA-nondiploidy, high S-phase fraction, HER2 amplification, and short term (≤2 years) distant disease-free survival (DDFS), independent of ER status. High expression of EGFR was strongly associated to ER negativity and also correlated with progesterone receptor negativity, high S-phase fraction, and inversely correlated with nodal metastases. In univariate analysis, high EGFR was associated with shorter DDFS (hazard ratio 2.1; P = 0.017), and reached borderline significance in a multivariate analysis, adjusting for ER, menopausal and lymph node status, tumor size, and HER2 (P = 0.057).

In conclusion, both AIB1 and EGFR were associated to DDFS for breast cancer patients treated with two years of adjuvant tamoxifen; AIB1 with the development of early distant recurrences, indicating association between high AIB1 and resistance to tamoxifen during treatment, and EGFR with distant recurrences up to a follow up of five years.