Incidence of brain metastases in early stage HER2 3+ breast cancer patients; is there a role for brain CT in asymptomatic patients?

Human epidermal growth factor receptor 2 overexpression (HER2 3+) is reported in retrospective studies as a factor that contributes to higher incidence of brain metastases (BM) in patients with metastatic breast carcinoma. Although there are some reports suggesting higher incidence of BM in adjuvant trastuzumab trials, the true incidence, as well as the time of occurrence of BM in early-stage high risk breast carcinoma patients, has not been widely prospectively explored. The main objective of this study was to prospectively explore the incidence of BM during and after adjuvant trastuzumab administration in HER2 3+ early-breast carcinoma patients. Two hundred and fifty-eight patients with early, HER2 3+ breast carcinoma have been included in this analysis. Brain computed tomography (CT) scan was scheduled once during adjuvant trastuzumab therapy and thereafter only if central nervous system (CNS) symptoms occurred. Eighty-five patients (33%) underwent brain CT in the absence of CNS symptoms. The median number of trastuzumab cycles at the time of brain CT was 9 (range 4-18). There were no BM detected by brain CT in these 85 asymptomatic patients. However, during a median follow up of 18 months 5/258 patients (1.93%) developed BM, but only 2 (0.77%) while still receiving adjuvant trastuzumab. The median time from breast cancer diagnosis to BM was 24 months (range 14-43). BM are a rare event during adjuvant trastuzumab treatment and brain CT screening is not justified in asymptomatic patients with early HER2 3+ breast carcinoma.