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Targeted therapy of lung cancer refers to using agents specifically designed to selectively target molecular pathways responsible for, or that substantially drive, the malignant phenotype of lung cancer cells, and as a consequence of this (relative) selectivity, cause fewer toxic effects on normal cells. Most previous chemotherapy drugs for cancer were (relatively) nonselective in their activity. Although their exact mechanisms of action were varied and complex, they generally worked by damaging cells undergoing mitosis, which is usually more common in malignant tumors than in most normal tissues. Targeted agents are designed to be selective in their effects by modulating the activity of proteins necessary and essential for oncogenesis and maintenance of cancer, particularly enzymes driving the uncontrolled growth, angiogenesis, invasiveness, and metastasis characteristic of malignant tumors. The increased differential activity usually results in fewer troubling side effects for cancer patients, particularly less nausea, vomiting, and death of cells in the bone marrow and gastrointestinal tract, and increased effectiveness against tumor cells. ==Traditional lung cancer classification and treatment== Lung cancer is an extremely heterogeneous family of malignant neoplasms, with well over 50 different histological variants recognized under the 4th revision of the World Health Organization (WHO) typing system, currently the most widely used lung cancer classification scheme.〔Travis WD, Brambilla E, Muller-Hermelink HK, Harris CC (Eds.): World Health Organization Classification of Tumours. Pathology and Genetics of Tumours of the Lung, Pleura, Thymus and Heart. IARC Press: Lyon 2004.〕 Because these variants have differing genetic, biological, and clinical properties, including response to treatment, correct classification of lung cancer cases are necessary to assure that lung cancer patients receive optimum management.〔Rossi G, Marchioni A, Sartori1 G, Longo L, Piccinini S, Cavazza A. (Histotype in non-small cell lung cancer therapy and staging: The emerging role of an old and underrated factor. ) Curr Resp Med Rev 2007; 3: 69-77.〕 Approximately 98% of lung cancers are carcinoma, a term describing malignancies derived from transformed cells exhibiting characteristics of epithelium. About 2% of all lung cancers are non-carcinoma (mainly sarcoma, tumors of hematopoietic origin, or germ cell tumors. These forms of lung cancer are usually treated differently from carcinomas. Because of the ubiquity of lung carcinomas, however, the term "lung cancer" generally refers to carcinomas in everyday clinical practice. Despite the large number of histological variants of lung carcinoma, oncologists have long tended to favor a dichotomous division into small cell and non-small cell forms, based on differences in clinical behavior and response to treatment. Most small cell lung carcinomas (SCLC's) metastasize to distant organs early on in their course, rendering surgery ineffective in curing the cancer. In contrast, non-small cell lung carcinomas (NSCLC's) are more likely to remain localized to the thorax during development, and are thus more amenable to cure using radical surgical resection. Additionally, SCLC's are typically much more sensitive to chemotherapy and/or radiation therapy than are NSCLC's. Therefore, current traditional treatment guidelines and standards of care recommend, when possible, the use of surgery for NSCLC, and chemotherapy with or without radiotherapy for SCLC. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Targeted therapy of lung cancer」の詳細全文を読む スポンサード リンク
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