Cross-sectional observational study to describe the clinicopathological and biological characteristics and the management of patients with HER2+ metastatic breast cancer who experienced complete or partial remission or disease stabilization during at least 3 years: LongHer study.

Abstract

e11081 Background: Trastuzumab has shown an improvement in survival outcomes among patients with HER2+ metastatic breast cancer (MBC). Identification of factors and tumor molecular profiles that may predict long-term remission has become a key-issue. Methods: Multicenter, observational, cross-sectional study. Data were collected from women with HER2+ MBC treated with a trastuzumab-based regimen that experienced CR, PR or SD during at least 3 years. FFPE samples(at least 70% tumor cells)for Microarray Analysis were obtained. L2 Boosting for classification with classical Akaike Information criterion based on the binomial log-likelihood for stopping the boosting iterations algorithm was applied to RNA expression data, to identify variables related to clinical information. Predictive models of long term response were built using a Binary Logistic Regression with the Fisher's scoring. Results: 103 patients.Median age: 58(51-68) years. Metastatic disease diagnosed after a median of 24.7(1.8-51.9) months since primary diagnosis. Predominant type: ductal carcinoma(91.9%) and 59% histological grade III. Hormonal status: Progesterone receptor positive 39.2% and estrogen receptor positive 41.2%. Most common metastatic sites: multiple locations(31.4%), lung(23.5%), bone(14.7%) and liver(13.7%). Overexpression of HER2 assessed by IHC in 98.1% of patients, 91.1% were HER2+(3+) and 18.4% had FISH+ HER2 status. Tumor was positive for p53 (>30%) and Ki67(>20%) in 47.3% and 73.6%. Surgery: 87.4% of patients, 77.5% radical mastectomy. Surgery of metastases was performed on 16.8%. Trastuzumab used in combination in 88.3% with a median number of cycles of 35.5(7.0-46). 68.9% of patients achieved a CR, 20.4% PR and 10.7% had SD, during an overall median time of 55 (43-79) months. 4 patients discontinued trastuzumab due to toxicity. Conclusions: Trastuzumab may provide a substantial long-term survival benefit with a manageable safety profile in these patients. Molecular analysis will be presented in the forthcoming Congress.