The stage of a cancer is a measure of the extent to which a cancer has spread in the body. Staging involves evaluation of a cancer's size and its penetration into surrounding tissue as well as the presence or absence of metastases in the lymph nodes or other organs. Staging is important for determining how a particular cancer should be treated, since lung-cancer therapies are geared toward specific stages. Staging of a cancer also is critical in estimating the prognosis of a given patient, with higher-stage cancers generally having a worse prognosis than lower-stage cancers.
Doctors may use several tests to accurately stage a lung cancer, including laboratory (blood chemistry) tests, X-rays, CT scans, bone scans, MRI scans, and PET scans. Abnormal blood chemistry tests may signal the presence of metastases in bone or liver, and radiological procedures can document the size of a cancer as well as its spread.
NSCLC are assigned a stage from I to IV in order of severity:
- In stage I, the cancer is confined to the lung.
- In stages II and III, the cancer is confined to the chest (with larger and more invasive tumors classified as stage III).
- Stage IV cancer has spread from the chest to other parts of the body.
SCLC are staged using a two-tiered system:
- Limited-stage (LS) SCLC refers to cancer that is confined to its area of origin in the chest.
- In extensive-stage (ES) SCLC, the cancer has spread beyond the chest to other parts of the body.
