Central nervous system metastases in women with HER-2 positive metastatic breast cancer after treatment with trastuzumab

Background: Historically, central nervous system (CNS) metastases have been reported to occur in 10–16% of women with metastatic breast cancer (MBC) with a median survival of less than 1 year after diagnosis of CNS disease. A higher rate of CNS metastases has been described in women with metastatic breast cancer (MBC) over‐expressing HER‐2 who receive trastuzumab therapy. Aims: The aim of this study was to examine the frequency of and potential risk factors for CNS metastases in these women. Our a priori hypotheses were that in MBC patients treated with trastuzumab, CNS metastases occurred (i) more frequently than historical controls, and (ii) in women with controlled systemic disease. Methods: A retrospective cohort study of 28 consecutive patients with MBC over‐expressing HER‐2 and treated with trastuzumab and chemotherapy was performed. Results: A total of 22/25 (88%) patients who initially responded to trastuzumab had progressed within a median of 11.2 months after starting trastuzumab therapy. Central nervous system metastases occurred in 11/28 (39%) patients and the remaining 11 patients had progressed elsewhere. At diagnosis of CNS metastases, 9/11 (82%) had controlled systemic disease (CR = 2, PR = 6, SD = 1). There were trends for patients with CNS metastases to have greater than one site of metastatic disease at the commencement of trastuzumab therapy (P = 0.06), and to be hormone receptor negative at initial diagnosis (P = 0.14). The median time to diagnosis of CNS metastases after the commencement of trastuzumab therapy was 12 months (range 6–19 months). The median survival after diagnosis of CNS metastases was 12 months (range 2–22 months). Conclusions: This study demonstrates a high rate of CNS metastases (39%) in HER‐2 positive MBC patients treated with trastuzumab. At CNS metastases most patients had controlled systemic disease and the median survival after CNS relapse was 1 year. We suggest aggressive management of CNS disease in this population. Additional strategies to decrease the incidence of CNS metastases in these patients may include prophylactic whole brain irradiation and the development of novel pharmacological agents with successful CNS penetration.