Biological behavior of HER2+ breast cancer: Differences based in hormone receptor expression.

person Maria Joao Ribeiro Da Silva Portuguese Oncology Institute Of Porto, Porto, Portugal info_outline Maria Joao Ribeiro Da Silva, Miguel Henriques Abreu, Sergio Xavier Azevedo, Tiago Alpoim, Susana Sousa, Deolinda Pereira

Authors person Maria Joao Ribeiro Da Silva Portuguese Oncology Institute Of Porto, Porto, Portugal info_outline Maria Joao Ribeiro Da Silva, Miguel Henriques Abreu, Sergio Xavier Azevedo, Tiago Alpoim, Susana Sousa, Deolinda Pereira Organizations Portuguese Oncology Institute Of Porto, Porto, Portugal, Department of Medical Oncology, Portuguese Institute of Oncology of Porto, Porto, Portugal, Centro Hospitalar de Santo António, Porto, Portugal, Portuguese Oncology Institute of Porto, Porto, Portugal, Department of Medical Oncology, Portuguese Oncology Institute, Porto, Portugal Abstract Disclosures Research Funding Other Foundation Background: Breast carcinoma is a heterogeneous disease whose therapeutic approach idepends on the classification into molecular subtypes. Despite the impact the expression of hormone receptors (HR) among patients with overexpression of HER2 is already the target of some studies, there is a lack of analysis in the era of treatment with adjuvant trastuzumab. Methods: This stydy consists in a retrospective analysis of cases of tumors with overexpression of the HER2 receptor (HER2 +), and HR- treated at an oncological center, comparing their biological behavior with cases of HR +/ HER2 + tumors, thus controlling for classic prognosis. Results: We analised a total of 420 patients, of whom 210 with HR+/HER2+ tumors and 210 HR- / HER2 +, with median ages of 52 years and 53 years, respectively. They accounted for 89.5% of cases of stage I to III disease. The groups were balanced in clinical characteristics. There was a higher proportion of undifferentiated and inflammatory tumors in the RH-/ HER2 + group, and in this group higher rates of complete pathological responses to treatment were observed (50.8% vs. 30.0%, p < 0.001). During the follow-up 30 recurrences occurred, 18 in the HR- / HER2 + group, and 12 in the HR + / HER2 +. There was lower disease-free survival in the HR-/HER2 +, on average 69.1 months, compared to 74.3 months in the group HR+/HER2 + (p = 0.001). The first metastatic site involved visceral location in 13 cases (72.2%) in HR- / HER2 + tumors (CNS involved in 8 cases), and in 8 cases (66.6%) in HR + / HER2 + tumors (CNS in 1 case). There was an association between relapse and response to primary systemic treatment (p = 0.003), with no relation demonstrated with other clinicopathological characteristics. In the global sample, there were 28 deaths, corresponding to 17 in the HR-/HER2 +, and 11 in the HR+/HER2 + group. There were significant diferences in OS, showing worse prognosis of HR- disease (mean of 70.7 months vs. 106.6 months, p = 0.001). There was an association of mortality with the presentation as an inflammatory tumor and involvement of the CNS. Conclusions: This study supports the concept of two distinct entities according to the expression in HER2 + disease, justifying therapeutic approaches and eventually different follow-up strategies.