CSCO expert consensus on the diagnosis and treatment of breast cancer brain metastasis

Breast cancer is one of the most common malignancies among women worldwide. According to the International Agency for Research on Cancer, breast cancer affected more Chinese women than any other cancer in 2020. The brain is an increasingly common metastatic sites of breast cancer. Although the risk of developing brain metastases (BMs) is lower in breast cancer than in lung cancer and melanoma, due to its high prevalence, it is the second most common cause of BM among solid tumors, being second only to lung cancer. The incidence of breast cancer brain metastasis (BCBM) differs by molecular subtype. Half of patients with advanced human epidermal growth factor receptor-2 (HER2)-positive and one-third of patients with triple-negative breast cancer (TNBC) develop BM. The clinical manifestations of leptomeningeal metastasis (LM) are often non-specific and may manifest as a variety of signs and symptoms, mainly including brain parenchyma involvement and meningeal irritation syndromes cranial nerve involvement, increased intracranial pressure, and progressive brain dysfunction. Therefore, the Chinese Society of Clinical Oncology (CSCO) Breast Cancer Committee has developed this expert consensus on BM, in an effort to improve the overall prognosis of BCBM and promote the standardized diagnosis and treatment of this disease. During the development of this expert consensus, we carried out a comprehensive literature review and referred to some of the most authoritative guidelines in China and abroad. In this consensus, we will discuss clinical manifestations, imaging examinations, pathological diagnosis, treatments, prognosis, follow-up and monitoring. We hope this consensus will be of help to all the clinicians majored in breast cancer and other similar professions.