Prognostic Factors and Survival According to Tumor Subtype in Women With Breast Cancer Brain Metastases

Abstract

Breast cancer (BC) is the second most cause of central nervous system (CNS) metastases. Studies report that almost one third of patients (pts) with triple-negative, one-third with human epidermal growth factor receptor 2 (HER2)-positive and 15% of those with hormone receptor-positive, HER2-negative metastatic breast cancer will develop brain metastases. It is known that the development of symptomatic brain metastases in women with advanced breast cancer is associated with poor prognosis, irrespective of local and systemic treatments. In the present study, we aim to determine the association between BC subtypes and CNS metastases occurrence and prognosis. Retrospective analysis of 309 BC patients with CNS metastases, confirmed by pathological and/or radiological methods, treated in a Cancer Center between 2003 and 2021, was obtained to identify clinicopathologic factors associated with early onset of brain metastases and survival outcomes. For analysis purposes, 3 BC subtypes were considered according to hormone receptor status and HER-2 expression: ER and/or PR positive, HER-2 positive and triple negative. The median time between diagnosis of BC and detection of CNS metastases was 43 months, and it was significantly shorter in triple negative group (8 months). Twenty-one patients (6,8%) had CNS metastases at BC diagnosis, with CNS being the first site of recurrence in 35,3%, mainly in HER2 positive. Most of the patients had parenchymal metastases (n = 245) and 37 (12%) had leptomeningeal (LM) disease, with predominance in ER and/or PR positive subtype (70,3%). In patients submitted to CNS surgery, the concordance between primary tumor and metastases subtype was higher in triple negative (76,9%) compared to 63,2% in HER-2 positive and 38,9% in ER and/or PR positive group (P < 0.05). After CNS involvement, 25,4% (n = 34) of patients with triple negative disease did not receive any systemic therapy, compared to 30,6% (n = 41) in HER-2 positive and 44% (n = 59) in ER and/or PR positive groups (P = 0.05). Median survival after CNS metastases was 9 months, but significantly longer in HER-2 positive group (16 months) and in patients submitted to surgical resection of CNS metastases, irrespectively of subtype (22 months vs 5 months in other treatment modalities). In multivariate Cox regression analysis, having HER-2 positive tumor was an independent prognostic factor for increasing survival after CNS metastases (HR 0.60, 95% CI: 0.41-0.87, P = 0.007), regardless the therapeutic strategy. Clinical behavior and prognosis of CNS metastases varies according to BC subtype. The association between LM disease and ER and/or PR positive tumors should be explored in upcoming studies. Also, these patients' prognosis depends on the availability of specific treatment options, therefore, innovative and effective therapeutic approaches are needed, in order to improve survival and quality of life of these patients.

Keywords: Brain metastases; Breast cancer; Central nervous system metastasis; Her2 positive breast cancer; Luminal breast cancer; Triple negative breast cancer.