Proactive Brain Screening Using Contrast-Enhanced Brain CT Scans in HER2+ Metastatic Breast Cancer

Purpose: According to recent EANO-ESMO guidelines, proactive brain imaging can be considered in asymptomatic patients with HER2+ metastatic breast cancer (mBC), due to high risk of developing brain metastases (BMs). However, optimal imaging modality and timing remain unclear. We retrospectively assessed the impact of contrast-enhanced CT screening on symptomatic BMs in HER2+ mBC patients. Methods: Consecutive patients newly diagnosed with HER2+ mBC treated with trastuzumab-pertuzumab plus taxane (2014-2024) were retrospectively identified. Brain screening was defined as at least one contrast-enhanced brain CT scan per year without neurological symptoms during the first 2 years post-diagnosis. Results: Among 148 identified patients, 73 underwent brain screening and 75 did not. Median number of annual brain CT scans during the first 2 years was 2.0 (IQR 1.2-2.5) and 0.0 (IQR 0.0-0.5) in the screening and non-screening groups, respectively. Thirty patients (20.3%) developed BMs during the first 2 years. Cumulative BM incidence was significantly higher in patients undergoing screening (30.6% vs 12.3%, Gray's p=0.004), but symptomatic BMs were significantly lower in patients undergoing screening (0% vs 9.5%, Gray's p=0.012). Patients undergoing screening had better preserved performance status at BM diagnosis (p=0.002) and a numerical trend toward fewer BMs (p=0.057). Treatment patterns post-BM diagnosis were similar, though WBRT was used less often in the screening group (14.3% vs 44.4%, p=0.073). Conclusions: Brain screening with CT scans was associated with fewer symptomatic BMs and better performance status at BM diagnosis, supporting proactive imaging in HER2+ mBC. Prospective studies are warranted to define optimal timing and imaging modalities.