A lot of research has been conducted and continues to be conducted into finding a cure for breast cancer. The various clinical research efforts have focused on various factors that improve the chances of a cure. How to detect the disease as early as possible is still getting a lot attention among researchers. Screening for early cases has gone beyond regular breast-exam and mammography to magnetic resonance imaging (MRI) and blood circulating tumor cell (CTC) count.
Diagnostic techniques have gone beyond total excision lymph node biopsy to sentinel lymph node biopsy, microwave breast tissue density measurement, and oncotype DX genomic testing. Risk factor identification has gone beyond age, gender and hormone sensitivity to intracellular receptor proteins and specific breast cancer genes like BRCA1 and BRCA2.
Similar strides have also been made in the treatment modalities. The broad treatment options have expanded beyond surgical excision, radiotherapy and chemotherapy to include biotherapy, and genetic engineering of T-lymphocytes. Breast cancer surgery now starts with a minimally invasive surgery to excise little breast tissue and one or two sentinel axillary lymph nodes. A radical surgery to remove the breast(s) and dissect all axillary lymph nodes is now only indicated by a high risk rating or a lymph node biopsy test suggesting disseminated disease.
Radiotherapy has advanced from non-selective irradiation of both cancerous and non-cancerous tissues to selectively focused radiation delivery techniques including radioactive breast tissue implants. Chemotherapy has also gone beyond non-selective cytotoxic (cancer-killing) drugs to highly tissue/cell specific cytotoxic drugs..Such tissue specific cytotoxic drugs (ADCs) are now tagged onto monoclonal antibodies to the proteins expressed on the cancer cells via stable linkers. The ADCs are then engulfed by endocytosis into the cancer cell lysosomes, where they are discharged to destroy the cells.
Biotherapy now targets the biochemical pathways that lead to the overexpression of the various cancer tissue growth factors to inhibit them, or induce the expression of genes that suppress the growth of cancer cells. It is also targeting energy supply pathways to disrupt them. Genetic engineering is currently being used to redirect T-lymphocytes that have the natural ability to destroy viruses toward cancer cells with encoded instructions to destroy them from the inside.
Excess Human Epidermal Growth Factor Receptor 2 protein (HER2) has been found in up to 30% of breast cancer patients, thereby making it a major risk factor and a negative survival indicator. It has been understood that ER (Estrogen Receptor) and PR (Progesterone Receptor), which tend to be increased along with HER2, are not as reliable as the latter for risk estimation. HER2 status measurement has become mandatory for proper diagnosis and treatment planning. (continued in Part II).
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