P11.54.A BRAIN RELAPSE IN HER2-POSITIVE BREAST CANCER AFTER NEOADJUVANT TREATMENT: AN INTERNATIONAL MULTICENTRIC STUDY

Abstract

Abstract BACKGROUND The incidence of central nervous system relapse among patients with breast cancer appears to be increasing, despite advances in systemic treatment. Although achieving pathological complete response (pCR) following neoadjuvant treatment has been associated with improved survival outcomes, it does not seem to prevent brain relapse. In early stage HER 2 positive disease between 10-14% will develop brain metastases and the risk is higher in endocrine receptor-negative setting. Identifying patients who are at greater risk of brain relapse can help to indicate those who need new treatment options to prevent it. This study aimed to assess the incidence of brain relapse in a multicenter cohort of patients who underwent neoadjuvant treatment across nine hospitals located in Portugal, Spain, and Chile, and to identify factors associated with it. MATERIAL AND METHODS We conducted a retrospective analysis of patients diagnosed and treated for HER2-positive breast cancer in nine hospitals located in Portugal, Spain, and Chile between January 2017 and December 2022. To be eligible for inclusion, patients must have undergone neoadjuvant anti-HER2 therapy followed by surgery. Data such as age at diagnosis, endocrine receptor expression, chemotherapy regimen, pathological response, adjuvant anti-HER2 treatment, endocrine therapy, and first local of relapse were analysed. RESULTS A total of 396 patients with a mean age of 52.9 years were included in the study. All patients received a neoadjuvant chemotherapy regimen and double anti-HER2 therapy with trastuzumab and pertuzumab, with a pathological complete response (pCR) achieved in 59.6% of patients. Nearly all patients (98.2%) received adjuvant anti-HER2 therapy, with 83.81% receiving trastuzumab, 12.85% receiving TDM1, and 3.34% receiving trastuzumab plus pertuzumab. Over a follow-up period of 3.5 years, 23 patients (5.81%) experienced relapse. Among these cases, 10 patients (2.5%) had brain relapse as first site, accounting for 43.48% of the total recurrences. Brain relapse was not associated with pathological response, but rather with a more advanced stage at diagnosis (T3/4 or Nodal positive) (p<0.05). CONCLUSION In CONCLUSION , our multicentric cohort study provides valuable insights into the incidence and factors associated with brain metastasis in HER2-positive breast cancer patients who underwent neoadjuvant treatment. Our findings suggest that although neoadjuvant treatment resulted in a high rate of pCR, it did not prevent brain relapse. Importantly, our study identified advanced disease stage at diagnosis as a significant risk factor for brain relapse. Further studies are needed to identify additional factors associated with brain metastasis and explore potential preventive strategies in patients with higher risk.