Question - What does it mean to say "Stage 4" cancer?
Stage of cancer is a shorthand description of the extent of cancer and the prognosis. Staging is specific for each type of cancer, however, staging of most cancers includes a description of the primary tumor (T stage), the status of the regional lymph nodes (N stage) and the presence or absence of distant metastasis (M stage). The combination of the T, N and M stages determines the stage group (stage 0, I, II, III or IV). Each stage group may have several sub-stages depending on the specific cancer (for example stage IIIb).
Stage O refers to non-invasive cancer and generally has an excellent prognosis. Stage I cancer is the most limited invasive cancer and typically has a good prognosis. Stage II and III cancers are intermediate in extent and have intermediate prognosis. Stage IV is the most extensive stage and carries the poorest prognosis.
Stage IV generally means cancer has spread to distant locations in the body (metastatic disease). There are also, however, a few instances in which stage IV does not apply even in the face of distant metastasis (for example, well differentiated thyroid cancer in a young individual). Also some cancers may be considered stage IV even in the absence of distant metastasis (for example, head and neck cancer which has extensively spread locally to adjacent structures).
The prognosis of stage IV cancer is poorer than earlier stage cancer. It must be noted that prognosis based on stage is accurate and reproducible for populations of patients (that is, it predicts accurately what happens on average). Individual patients may have outcomes not predicted by the stage. Early stage individual patients may do poorer than expected and late stage patients may do better than expected.
An excellent source of further information regarding the staging of most types of cancer can be found on the American Cancer Society website: http://www.cancer.org/docroot/home/index.asp
Richard F. Burroughs, MD