Phase II Trial of Brain MRI Surveillance in Stage IV Breast Cancer

Background: Screening of asymptomatic stage IV breast cancer with brain MRIs is currently not recommended by National Comprehensive Cancer Network (NCCN) Guidelines. The incidence of asymptomatic brain metastasis is not well documented.

Methods: The study is designed as a single arm, phase II trial, with the goal of investigating surveillance brain MRIs in neurologically asymptomatic patients with metastatic breast cancer. Breast cancer patients were classified into triple negative (TN), HER2+, and hormone receptor (HR)+/HER2-. Patients underwent a surveillance brain MRI and a second brain MRI at 6 months if the baseline MRI was negative. Asymptomatic, stage IV breast cancer patients, ECOG ≤2, and life expectancy ≥6 months were eligible. The primary objective was to determine the frequency of asymptomatic brain metastasis in metastatic breast cancer. Clinical trial information: NCT05115474.

Results: A total of 101 patients completed the surveillance brain MRI including 40 HR+/HER2-, 33 HER2+, and 28 TN patients. The overall frequency of brain metastasis on initial surveillance brain MRI was 14% (n=14) with rates of 18%, 15%, and 10% in TN, HER2+, and HR+/HER2- patients, respectively. Following the 6-month MRI, the cumulative rates of brain metastasis increased to 25% in TN, 24% in HER2+, and 23% in HR+/HER2- patients.

Conclusions: The highest frequency of brain metastases at baseline was in TN and HER2+ breast cancer. Following the 6-month MRI, the cumulative frequency was approximately a quarter across all subtypes. These results warrant confirmatory trials to refine brain MRI surveillance recommendations for neurologically asymptomatic stage IV breast cancer.