Abstract PO2-27-09: Clinical impact of routine MRI screening for brain metastases in patients with HER2 positive or triple negative metastatic breast cancer

Abstract Background: Routine screening for brain metastases (BMs) is currently not recommended in patients with metastatic breast cancer (BC). There is a growing consensus on the need for the screening of BMs in HER2 positive and triple negative breast cancer (TNBC) because 40% of patients experience BMs throughout the disease course and systemic treatment options with intracranial efficacy are now available. However, there is a lack of prospective study data on this matter. We conducted a prospective cohort study to evaluate the role of brain MRI screening for the patient with metastatic BC. Methods: Patients who newly diagnosed metastatic HER2+ or TNBC were eligible. Screening brain MRI was planned at diagnosis and failure from first line and second line of systemic therapy. All patients underwent complete physical examination and comprehensive neurologic assessment at baseline and thereafter. Patients who diagnosed symptomatic BMs were dropped from the study and subsequent treatment including local therapies and survival data were collected. Primary endpoint was the percentage of patients diagnosed with asymptomatic BMs. Results: A total of 147 patients were enrolled between Sep 2018 and Aug 2023 at Yonsei Cancer Center. The median age was 51 years (range, 29-80) and most patients (92.5%, n=136) had good performance status (ECOG 0-1). The tumor subtypes were as follows: TNBC, 51.0%; HER2 (ER-, HER2+), 29.3%; luminal-HER2 (ER+, HER2+), 19.7%. The cumulative incidence of asymptomatic BMs was 20.4% for overall patients; 24.0% for TNBC (18/75), 14.0% for HER2 (6/43), and 20.7% for luminal HER2 (6/29). Symptomatic detection of BMs during study period was 14.7% for TNBC, 18.6% for HER2, and 6.9% for luminal-HER2. Initial local treatment was stereotactic radiosurgery in 30 patients (58.8%), whole-brain radiation therapy in 14 patients (27.5%), surgical resection in 2 patients (3.9%) and 6 patients (11.8%) did not receive any treatment for BMs. After a median follow-up of 20.1 months, the median overall survival following a diagnosis of BMs was 23.7 vs 7.3 months (hazard ratio 0.41; 95% CI, 0.17 to 0.95; P = .04) in patients with asymptomatic and symptomatic BMs, respectively. Conclusions: We identified approximately 20% of patients with HER2+ or TNBC as asymptomatic BMs. Emerging systemic therapies showed promising intracranial response would warrant the detection of asymptomatic BMs through routine MRI screening. Incidence of brain metastases by subtypes Citation Format: Gun Min Kim, Joo Hyuk Sohn, Min Hwan Kim, Seul-Gi Kim, Hyung Soon Park, Jong Hee Jang, Yong Bae Kim, Seung-koo Lee. Clinical impact of routine MRI screening for brain metastases in patients with HER2 positive or triple negative metastatic breast cancer 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 PO2-27-09.