中 国 药 科 大 学
Bachelors Research Proposal
A systematic review of breast cancer and early onset of brain metastasis
GENERAL INTRODUCTION
Cancer is a heterogeneous disease characterized by uncontrolled growth and spread of malignant cells harboring genetic or epigenetic alterations. Globally, breast cancer is the most commonly diagnosed malignancy causing the highest number of cancer-related deaths among women [1]. Breast cancer survival is associated with the metastatic potential of the tumor indeed 90 % of patientsrsquo; deaths are caused by local invasion and distant metastasis of tumor cells [2].
Metastasis – the dissemination of tumour cells from the primary tumour and growth at secondary sites – is the major cause of mortality in cancer patients and may occur years and even decades after successful removal of the primary tumour and adjuvant therapy [3]. On average, the median latency between the initial diagnosis of breast cancer and the onset of brain metastasis is 2 to 3 years. In most cases, breast cancer patients develop brain metastases after metastases have appeared systemically in the lung, liver, and/or bone [4]. Once the lesion disseminates to brain, average patient survival time is less than 1 year, and treatments including chemotherapy, radiation, and surgery are the primarily palliative options [5].
Breast cancer is a common cause of brain metastases, with metastases occurring in at least 10–16 % of patients. Longer survival of patients with metastatic breast cancer and the use of better imaging techniques are associated with an increased incidence of brain metastases [6]. The overall prognosis of breast cancer patients with brain metastases remains poor, and these metastases are less responsive to systemic therapies. Brain metastasis is associated with a reduced quality of life due to progressive neurologic impairments. Recently, a trend of increased incidence of brain metastases in breast cancer has been noted [7]. Breast cancer is no longer viewed as a homogenous disease process, but rather as a compilation of reproducibly identified intrinsic subtypes as defined by microarray (luminal A, luminal B, basal-like, and human epidermal growth factor receptor 2 [HER2]-enriched subtypes), each characterized by unique clinicopathologic features and a distinct prognosis [8]. Studies have found increased risk of brain metastases in patients with HER-2 positive BC and prognosis is usually poor [9].
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