A prospective study for brain metastasis imaging screening in patients with advanced HER2-positive or triple-negative breast cancer

Background: Current guidelines for advanced breast cancer do not recommend routine brain imaging in neurologically asymptomatic patients. Prospective clinical evidence on the effectiveness of screening for early detection of brain metastasis (BM) remains limited. We conducted a prospective cohort study to evaluate the utility of magnetic resonance imaging (MRI) screening in patients with advanced human epidermal growth factor receptor 2-positive (HER2+) or triple-negative breast cancer (TNBC). Patients and methods: In this single-arm, prospective study, screening brain MRI was carried out at diagnosis in asymptomatic patients with advanced HER2+ or TNBC. Patients without BM on baseline MRI were monitored for the development of neurologic symptoms. Follow-up brain MRI studies were carried out at the initiation of second- and third-line systemic therapy. The primary endpoint was the detection rate of BM on screening MRI. Results: MRI detected asymptomatic BM in 11/112 (9.8%) patients at baseline; the cumulative detection rates increased to 17.0% and 19.6% by the initiation of second- and third-line therapy, respectively. Through this serial screening strategy, two-thirds of all BM cases (22/33) were identified at an asymptomatic stage. Patients with baseline metastatic involvement of three or more organ sites outside the central nervous system had an increased risk of BM (hazard ratio 3.38), and 38.5% of patients in this subgroup were diagnosed with BM by MRI screening. Stereotactic radiosurgery (66.7%) was the most common initial treatment for BM, and the median overall survival after BM diagnosis was 23.3 months. Conclusions: Two-thirds of BM cases in patients with advanced HER2+ or TNBC were diagnosed at an asymptomatic stage in this prospective serial brain MRI screening program.