Lung cancer is a disease characterized by uncontrolled cell growth in tissues of the lung. This uncontrolled growth may lead to cells invading surrounding tissues or spreading to the organs outside the lungs.
Lung cancer was a rare disease in early 20th century but its incidence has gradually increased with increased smoking and it has become the most common type of cancer in the world. The lung cancers accounts for 12.8% of cancer cases and 17.8% of mortalities of cancer worldwide.
The incidence of lung cancer increases with age and peaks at 6th and 7th decades. It is less common in young adults (under 50 years old, around 5-10%). This community has often a family history and adenocancer is the most common type of cancer. However, the incidence of adenocancer is higher in young adults than in elderly in the country, and the most common type of cancer is squamous cell carcinoma. The incidence of lung cancer increases in women with increased smoking.
Lung cancer is a preventable disease. The factors that play a role in cancer development include tobacco products, industrial products (uranium, radiation, asbestos) air pollution, and nutritional deficiencies. Recent studies have demonstrated that the critical factor increasing the risk of lung cancer is the long-term respiration of carcinogenic materials. Epidemiologic case-control studies by 1950s proved that smoking was strongly correlated with lung cancer. The first findings that smoking was a cause of lung cancer were published in 1962. Smoking is responsible for developing lung cancer by 94%. The risk of lung cancer is 24-36 times higher in smokers than in non-smokers. The risk is 3.5% in passive smoking. Age to start smoking, period of smoking, number of cigarettes smoked, and type of tobacco and cigarette have influence on the risk of developing lung cancer.
Symptoms of lung cancer may vary depending on location of the disease, how it has spread, and presence of reaction of the body to disease. The most common symptoms include shortness of breath, cough and weight loss. Since these symptoms are not only specific to lung cancer, the patients may be diagnosed late. Chest radiography and computerized tomography (CT) are used to diagnose lung cancer. Positron emission tomography (PET) provides information on if the tumor is benign or malignant, or if it has spread to any organs outside the lungs. It is a method that is highly effective in diagnosing solitary pulmonary nodules. The final diagnosis of lung cancer is established by biopsy. Biopsy is usually performed by bronchoscopy or CT-assisted biopsy. Factors determining the treatment and prognosis are histological type of cancer, stage of cancer, and general performance of the patient. Despite many histological subtypes of lung cancer, clinical types are small cell and non-small cell lung cancer. It is important to identify the type of cancer cells for treatment planning and prognosis because this will help determine the way to follow for treatment. Chemotherapy and radiotherapy are chosen for small cell lung cancer whereas the first option is surgery for non-small cell lung cancers.
Surgical treatment in early stage of lung cancer can prolong the length of life up to 85%. There is no chance to cure an advanced stage non-small cell lung cancer. Response rate or survival period is not a criterion alone in evaluating treatments. Small cell lung cancer is a more aggressive tumor and has a higher rate of distant metastasis. However, response to chemotherapy is higher. Palliation of symptoms should improve the quality of life and prolong the survival.
Radiotherapy is often prescribed with chemotherapy and can be used for therapeutic purposes in patients with non-small cell lung cancer that are not suitable for surgery. Therapeutic radiotherapy is administrated at high doses which is called radical radiotherapy. It has a curative potential for patients with small cell lung cancer. Administration of radiotherapy on the chest in addition to chemotherapy is often prescribed.
Several targeted treatment methods for cancer have recently been developed at various molecular levels for patients with advanced stage cancer. Majority of the patients with non-small cell lung cancer has epidermal growth factor receptor (EGFR). Therefore drugs targeting on tyrosine kinase in epidermal growth factor receptor have been developed. Developments in cytotoxic drugs, pharmacogenetics and targeted drugs are promising. Although most of the targeted drugs have been clinically researched, they are only in the early stage of clinical.