Lung Cancer

Lung cancer is the uncontrolled growth of abnormal cells in one or both lungs. The abnormal cells reproduce rapidly and form lumps of cancer cells (tumors) that disrupt the lung, making it difficult to function properly. The results of different studies indicate that 85 to 95 percent of lung cancers are smoking related, including second hand smoking-related causes. Environmental factors also play a significant role in causing lung cancer. The most effective prevention of lung cancer is to quit smoking, although this habit is extremely hard to quit for heavy smokers or people who started to smoke at an early age. Furthermore, the risk for smokers remain elevated for several years after quitting, therefore life long abstinence from smoking is considered the best way of preventing lung cancers. The signs and symptoms of lung cancer, such as persistent cough and chest pain, may take several years to appear, and they are often confused with the symptoms of less serious conditions. Therefore, they may not be detected correctly until the disease reaches an advanced stage. The treatment consists of surgical removal of the tumor and surrounding tissue, chemotherapy, radiation therapy, or some combination of these methods. There are also new types of therapies that are still being investigated, such as monoclonal antibodies (engineered antibodies that target specific protein cells) and photodynamic therapy (combination treatment with chemicals and light). Despite the scientific developments in its diagnosis and treatment, lung cancer is the leading cause of cancer deaths worldwide. It is the most common cancer in men and fifth most frequent cancer in women. However, lung cancer has become more prevalent among women worldwide since the 1970s because more women have started smoking and work in environmentally hazardous conditions. Lung cancer is more common in the developed countries, such as the United States and Western European countries; however, the percentage of five-year survival rate is also significantly higher in those countries than the developing countries, such as India and China due to the better medical services available in those countries.

Lung cancer is commonly defined as the uncontrolled growth of abnormal cells in one or both lungs. The lung cancer cells grow in an uncontrollable and unlimited way, and they “invade” the nearby normal tissue and destroy the organ structure. The abnormal cells reproduce rapidly in this process and form lumps of cancer cells (tumors) that disrupt the lung, making it difficult to function properly. These cells can also break down lung tissue structure and enter the bloodstream or lymphatic system, thus spread to distant organs in other parts of the body, a process that is called metastasis. Clinically, there are two types of lung cancer, which are differentiated according to their cell types under microscopy: non-small cell lung cancer and small cell lung cancer, which is also called oat cell cancer. Non-small cell lung cancer is the most common type of lung cancer in the world, and has three major categories: Adenocarcinoma, which is the most common type of lung cancer among women and people who have never smoked, squamous cell cancer, which is most common type of cancer among men, and large cell carcinoma. Small cell lung cancer develops in the central areas of the lung and it is the most aggressive type of lung cancer. It is found almost exclusively among smokers and it is [Page 1034]more likely to spread to other parts of the body than non-small cell lung cancer.

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