Understanding Cancer Staging: TNM and Stages 0-IV

Staging is a standardised way of describing how much cancer is in the body and where it is located. The most widely used method is the TNM system, which separately scores the size and extent of the primary Tumour, whether nearby lymph Nodes are involved, and whether there is distant Metastasis. These scores are then combined into an overall stage, usually expressed as stage 0 through stage IV, with higher numbers generally reflecting more extensive disease.

Learning your stage can help you understand the general approach your care team is recommending and what questions to ask about goals of treatment. It is important to remember that stage is a snapshot based on available tests, and that individual outcomes vary widely even within the same stage.

Symptoms are not part of the staging system itself, but the extent of disease reflected in the stage can influence which symptoms a person experiences. Earlier stage cancers may cause few or no symptoms, while more advanced or widespread disease is more likely to cause symptoms related to the organs involved.

Staging is typically completed shortly after a cancer diagnosis is confirmed, using a combination of physical examination, imaging studies, and pathology results from a biopsy. For some cancers, additional surgical staging procedures, such as lymph node biopsy, are needed to gather complete information.

Common tests used in staging include CT, MRI, and PET scans to look for tumour size and possible spread, along with blood tests and pathology review of biopsy or surgical specimens. The specific combination of tests depends on the type of cancer being staged.

Most solid tumours, including breast, lung, colorectal, and prostate cancers, use versions of the TNM system, though the specific criteria differ by cancer type. Some cancers, such as certain blood cancers, use different staging systems better suited to how those diseases behave, since they do not always form a discrete mass.

Treatment options are closely tied to stage: early stages often involve surgery or radiation aimed at removing or controlling localised disease, sometimes combined with systemic therapy, while later stages more often rely on systemic treatments such as chemotherapy, targeted therapy, or immunotherapy, sometimes alongside radiation for symptom control.