Lung cancer is an uncontrolled growth of cells that start off in the lungs. Instead of developing into healthy lung tissue, the cells divide rapidly and forms malignant tumours. These malignant tumours develop in the cells of the lungs is known as lung cancer. Usually, lung cancer starts in the cells that line the air passages and it can also spread to other parts of the body.

There are two types of lung cancers based on cell size:-

• Small cell lung cancer (SCLC)
• Non-small cell lung cancer (NSCLC). 

Radiation therapy uses high-energy x-rays (or particles) to kill cancer cells. Radiation may be used after surgery to help keep the tumor from coming back. So this is called as adjuvant therapy. Two types radiation surgery: A. External beam radiation therapy (focuses radiation on the cancer from a machine outside the body). B. Brachytherapy: For this type of treatment, the doctor places a small source of radioactive material (often in the form of small pellets) directly into the cancer or into the airway next to the cancer. This is usually done through a bronchoscope, but it may also be done during surgery.