Stage
How far a cancer has spread, from stage I (small and confined) to stage IV (spread to distant organs). Stage is the single strongest guide to treatment and prognosis.
Stage combines the size and local extent of the primary tumour, whether lymph nodes are involved, and whether there are distant metastases, formalised in the TNM system and grouped into stages I to IV; stage 0 is cancer in situ. Stages I to III are usually treated with curative intent by surgery or radiotherapy, often with drugs before or after, while stage IV is generally treated with systemic therapy to control rather than cure. Stage is determined by imaging and pathology at diagnosis ('clinical' and 'pathological' stage) and is not changed if the cancer later spreads, though the patient is then said to have metastatic or recurrent disease.