Does HER2/neu expression affect adjuvant treatment choices in routine clinical practice?

Abstract

10667 Background: HER2/neu (HER2) amplification is a recognized independent prognostic and predictive factor. We retrospectively examined the correlation between HER2 expression and adjuvant therapy in patients (pts) with early breast cancer (EBC) at our Institution (IOSI). Materials and Methods: From January 2003, 326 consecutive pts with EBC have been treated at IOSI and all clinical and pathological data have been prospectively collected into a specifically designed data base (CARMA). HER2 expression was assessed by the c-erbB-2 oncoprotein antibody (NCL-L-CB11) in 309 pts (95%). FISH was not routinely performed. Endocrine responsiveness (ER+) is defined as Er and/or PgR expression by immunohistochemistry. Results: Overall, 58 pts (19%) had HER2+ disease. FISH was performed in 15 pts (24%) with doubtful antibody overexpression (2+) and did not confirm HER2 amplification in 4 cases (27%). Nodal involvement was not assessed in 1 HER2+ (2%) and in 12 HER2- pts (5%) due to advanced age. Menopausal status did not differ in HER2 positive and negative pts (29% and 27% premenopausal pts, respectively). The distribution of adjuvant chemotherapy (CT) according to tumour characteristics in HER2 positive and negative pts was as follows: An anthracycline-containing regimen was chosen in 88% of HER2+ pts receiving adjuvant CT as compared to 70% of HER2- pts. Outside of a clinical trial adjuvant Tamoxifen was given to 57% of HER2+/ER+ pts as compared to 75% of HER2−/ER+ pts. Conclusions: Overall, HER2+ pts showed less endocrine responsiveness (64% versus 88%) and more extensive nodal involvement (43% versus 30% with >3 positive nodes) as compared to HER2− pts. A greater proportion of HER2+ women received adjuvant CT, irrespective of other prognostic and predictive factors. In particular, a significant higher proportion of HER2+ pts with minimal nodal involvement (1–3 positive nodes) and ER+ disease received CT as compared to the equivalent HER2- subset (45% versus 26%, respectively). [Table: see text] No significant financial relationships to disclose.