Abstract P3-06-05: HER2/HR positive early breast cancer patients have nowadays the highest disease-free survival: Results from the south-east of the Netherlands

Abstract

Abstract Background Adjuvant systemic therapy choices in early breast cancer largely depend on human epidermal growth factor receptor 2 (HER2) and hormone receptor (HR) status. Overexpression of HER2 has been shown to be associated with a worse outcome (Slamon et al, Science, 1987). With this cohort study, we aimed to assess the outcome of early breast cancer patients per subtype based on HER2 and HR status in daily practice treated in a time period of routine use of anti-HER2 treatment. Patients and methods Patients diagnosed with early breast cancer during the years 2005-2007 in five participating hospitals in the South-East part of the Netherlands were included. Patients with primary metastatic breast cancer were excluded. Information regarding disease characteristics and treatment was collected. Patients were categorized in 4 subtypes based on the HER2 and HR status of the primary tumor: HER2 positive (+)/HR positive (+), HER2 negative (-)/HR+, HER2+/HR-, and triple negative (TN) (i.e. HER2- and HR-). Disease-free survival (DFS) was estimated using the Kaplan-Meier method. Cox proportional hazards model was used to determine the prognostic impact of breast cancer subtype, adjusted for possible confounders. Results A total of 2579 patients were included with a median follow-up of 52.6 months. Median 5-year DFS rate was highest for the HER2+/HR+ subtype (comprising of 13% of all patients) with 78%, compared to 68% for the HER2+/HR- subtype (5% of all patients), 75% for the HER2-/HR+ subtype (70% of all patients) and 64% for the TN subtype (12% of all patients). In multivariate analysis, subtype was confirmed to be an independent prognostic factor. Compared to the HER2+/HR+ subtype, the HER2+/HR- subtype was associated with a worse DFS (HR 2.05, 95% CI 1.21-3.46, P = 0.008) and the HER2-/HR+ was associated with a similar DFS (HR 1.09, 95% CI 0.79-1.52, P = 0.6). Furthermore, classical clinicopathological parameters were all confirmed to be of independent prognostic relevance, as well as the use of adjuvant systemic therapy. At the meeting, we will show the results according to the type of adjuvant systemic treatment used. Conclusion In this cohort, we noted that 13% of patients had HER2+/HR+ early breast cancer. These had the highest 5-year disease-free survival of all subtypes, significantly better than the HER2+/HR- subgroup. This may indicate a differential prognostic impact of HER2 according to HR status, with HR+ having a positive prognostic impact, irrespective of the presence of HER2 overexpression. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-06-05.