Abstract PO5-18-12: Can we cure de novo oligometastatic stage IV HER2+ breast cancer with multimodality therapy? (CHLOE)

Abstract Background: The current standard of care is to treat all patients with metastatic breast cancer with palliative intent, regardless of extent of disease. However, in real world practice patients with oligometastatic disease are sometimes treated with surgery and/or radiation/ablation in combination with systemic therapy to render them as having no evidence of disease. Previous randomized clinical trials have not shown a benefit to adding surgery or radiation in metastatic breast cancer, however, these trials had a small number of HER2+ patients. HER2+ patients are uniquely responsive to combination of chemotherapy and targeted HER2 therapy and therefore may have different outcomes with a multimodality approach. The goal of this project is to use a novel, user friendly, on-line clinical study platform that registers patients and enables follow-up data collection to test the hypothesis that de novo stage IV oligometastatic HER2+ patients treated with multimodality therapy may result in improved long-term distant metastasis free survival and overall survival. Trial design: This is a prospective, nationwide registry study that will enroll newly diagnosed (de novo) oligometastatic (operationally defined by local tumor boards as disease where all metastatic lesions can be ablated) HER2+ breast cancer. A secure online portal has been created by the Yale IT team in accordance with HIPPA and cybersecurity guidelines. Data will be directly entered into the online portal by participating investigators and information regarding what treatment the patient received, if they completed treatment, and survival data will be collected. All treatment decisions will be at the discretion of the treating provider. Eligibility criteria: Patients with de novo oligometastatic HER2+ breast cancer in whom local treatment of all metastatic sites by either surgery, radiation, or ablative techniques is feasible as determined by multidisciplinary discussion or local tumor board. Specific aims: Primary: To estimate the 3 year distant metastasis free survival in patients with de novo oligometastatic HER2+ breast cancer treated with a multi-modality treatment plan. Secondary: To estimate 3 year overall survival and to monitor QOL. Statistical methods: The major analysis will occur after at least 3 years following the last subject’s enrollment in a cohort, to ensure that the objective of distant metastasis free survival at 3 years will be analyzed. It will include: tabulation of all cases entered, number and location of metastases, if treatment plan was implemented, compliance rate of treatment delivery, observed results with respect to the primary endpoint. Kaplan-Meier estimates will be presented for the analysis of survival endpoints together with a summary of associated statistics (median survival time if reached, landmark survival rate estimates and estimates for every 6 months thereafter if applicable), including the corresponding two-sided 95% confidence intervals. The 95% exact Clopper Pearson confidence intervals will be presented for binary endpoints. Paired t-test or Wilcoxon signed rank test will be used to assess the difference of continuous variables measured at different time points. The secondary clinical outcome is overall survival at 3 years, defined as the percentage of patients without an event at the 3-year follow-up time point measured from the study registration date. An event is considered death from any cause. OS time will be measured from the date of randomization to the date of first OS failure or last follow-up. OS will be estimated by the Kaplan-Meier method with OS failure defined as: death from any cause. Present accrual and target accrual: 4/42 patients Contact information for people with a specific interest in the trial: Mariya.Rozenblit@yale.edu https://chloe.yalepathaws.org Citation Format: Mariya Rozenblit, Nathalie Wiesendanger, Kelly Shanahan, Christine Hodgdon, Peter Gershkovich, Mehra Golshan, Meena Moran, Maryam Lustberg, Lajos Pusztai. Can we cure de novo oligometastatic stage IV HER2+ breast cancer with multimodality therapy? (CHLOE) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-18-12.