How Is Cancer Staged? PART 2

If cancer cells have penetrated beyond the original layer of tissue, the cancer is invasive and categorized as local, regional, or distant stage based on the extent of spread. (For a description of the summary stage categories, see the footnotes in the table on page 17, Five-year RelativeSurvival Rates (%) by Stage at Diagnosis, 2002-2008.) Clinicians typically use the TNM cancer staging system, which assesses tumors in three ways: extent of the primary tumor (T), absence or presence of regional lymph node involvement (N), and absence or presence of distant metastases (M). Once the T, N, and M categories are determined, a stage of 0, I, II, III, or IV is assigned, with stage 0 being in situ, stage I being early, and stage IV being the most advanced disease. Some cancers have alternative staging systems (e.g., leukemia). As the molecular properties of cancer have become better understood, tumor biological markers and genetic features have been incorporated into prognostic models, treatment plans, and/or stage for some cancer sites.