Lung cancer is the main cause of cancer deaths for men and women, worldwide. The greatest factor behind the occurrence of this form of cancer is smoking. A disease in which the cells of lung tissues grow up uncontrollably and form tumors is known as lung cancer. It is most common between the age group 40 -70. Lung cancer is of two types: - primary and secondary. Primary lung cancer begins in the lungs. Secondary lung cancer begins in any part of the body; cancerous cells then spread to lungs which are termed as Metastasis. Lung cancer kills more than 1.3 million people worldwide every year.

There are many symptoms of lung cancer such as: - chest pain, chronic coughing, shortness of breath, cachexia (weight loss), loss of appetite, fatigue, dysphagia (difficulty in swallowing), hemoptysis (coughing up blood) etc.The most common cause or reason of lung cancer is smoking. Tobacco smoke is a carcinogen (cancer causing); long–term exposure to it causes changes to the DNA in the bronchial epithelium or the tissue lining the bronchi of the lungs. When large number of tissue gets damaged, ultimately a cancer develops. Cigarette smoking is the key contributor to lung cancer. Tobacco contains nicotine which lowers the immune response to harmful growths in exposed tissues.

It is estimated that 87% of lung cancer is responsible for smoking in the United States. Research suggests that passive smoking or secondhand smoke is also responsible for lung cancer. Smokers who consume wide variety of fruits and vegetables in a good quantity in their diet are less likely to develop lung diseases. Medical science claims that a smoker is safeguarded against lung cancer to a large extent, if he quits smoking. Smoking cessation will definitely reduce the vulnerability to lung cancer.