الفهرس 
Biological Classification of Breast CancerOnly 14 pages are availabe for public view
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Abstract
B
reast cancer is the most common cancer affecting women globally. It is the leading cause of death from cancer in women.
In North America and Western Europe, one in every eight or nine women will develop the disease during their lifetime.
The outcome of breast cancer is predicted by the extent of spread of the tumor to locoregional lymph nodes, which, in turn, predicts distant spread. Patients with advanced metastatic disease have a very poor prognosis, hence the importance of effective early diagnosis and treatment to prevent later recurrences and improve survival.
Early detection of breast cancer is the most effective way to reduce mortality, and a screening program based on mammography is considered the best method for early detection of breast cancer.
Breast conservation therapy has become the treatment standard for early stage breast cancer. Sentinel lymph node biopsy is a new procedure that can predict axillary lymph node dissection.
The targeted therapy refers to a new generation of anticancer drugs that are designed to interfere with a specific molecular target, usually a protein. This approach differs from the more empirical approach used in conventional cytotoxic chemotherapy. In contrast to conventional chemotherapy, it interferes with molecular targets that have a critical role in tumor growth or progression. Since it is directed against cancer specific molecules and signaling pathways, it has limited non-specific toxicities. The molecular targets are usually located in tumor cells, some like anti-angiogenic agents may target other cells such as endothelial cells. Targeted therapies have a high specificity toward tumor cells, providing a broader therapeutic window with less toxicity. They are also often useful in combination with cytotoxic chemotherapy or radiation to produce additive of synergistic anticancer activity because their toxicity profiles often do not overlap with traditional cytotoxic chemotherapy.
Targeting the oestrogen receptor (ER) is a molecular targeted therapy approach, and widespread use of the selective ER modulator tamoxifen in breast cancer is responsible for major improvements in cure rates, quality of life and disease prevention during the past 25 years. Targeting both HER-2 (human epidermal growth factor receptor 2) with trastuzumab and the vascular endothelial growth factor (VEGF) with bevacizumab in combination with chemotherapy has become a further milestone of molecular targeted therapy. However, intrinsic and acquired resistance to endocrine and/or cytostatic treatments is still a common feature that limits the benefits of these novel therapeutic strategies.
Treatments of breast cancer continue to evolve rapidly. Scientific and clinical achievements are constantly changing the standard of care and have already led to substantial reductions in breast cancer mortality. Despite encouraging preclinical data, some of the molecular targeted agents have yielded low response rates in the clinical setting.
A further issue is the successful management of side effects of these agents, such as acneform rash with anti-EGFR therapy, cardiac insufficiency with trastuzumab treatment, and hypertension and cerebrovascular ischaemia with bevacizumab therapy. New opportunities to select the right patient for a benefical therapy has resulted from knowledge of most of the genes in the human genome and the development of whole-genome gene expression analysis by array technology. Many studies have been performed whose aim is to achieve improved matching of effective drug(s) to the molecular characteristics of the individual cancer patient.
Targeted cancer therapies give doctors a better way to tailor cancer treatment, especially when a target is present in some but not all tumors of a particular type, as is the case for HER-2. Eventually, treatments may be individualized based on the unique set of molecular targets produced by the patient’s tumor. Targeted cancer therapies also hold the promise of being more selective for cancer cells than normal cells, thus harming fewer normal cells, reducing side effects, and improving quality of life. Nevertheless, targeted therapies have some limitations. Chief among these is the potential for cells to develop resistance to them.