Staging is very important and should be performed before treatment started. It is based on size of the tumor, location of the tumor, and degree of metastasis of the tumor. Staging is beneficial to plan a treatment program, to determine eligibility for surgery, to assess response by stage for results reporting and to estimate prognosis. The higher the tumor stage, the less likely the disease will be cured. Staging of tumor is according to the TNM classifications. T refers to the size and extent of the primary tumor, N refers to involvement of regional nodes and M refers to the presence or absence of metastatic disease.

There are different staging systems for small cell lung cancer and non-small cell lung cancer. Limited and extensive are the two stage system in SCLC. In limited stage, cancer is found only in one lung and in lymph nodes on the same side of the chest or in fluid around the lung. If the cancer has spread beyond one lung, to lymph nodes on the other side of the chest or to other organs, it is called extensive.

There are 4 stages for NSCLC. They are :

Stage 1 - It is very localised and tumor of any size is found only in the lung.
Stage 2 - Tumor has spread to lymph nodes associated with the affected lung
Stage 3 - Tumor has spread into the tissue around the lung near to where the cancer started. This can be into the chest wall, the covering of the lung (pleura), the middle of the chest (mediastinum) or other lymph nodes.
Stage 4 - Tumor has spread to another part of the body

There are many options for the treatment of lung cancer at each stage.