The American Joint Committee on Cancer (AJCC) has developed and compiled cancer staging references for quickly finding important information about different types of cancers. These references and tools are excellent resources for medical professionals treating patients with cancer.
Cancer staging is the process of determining how much cancer is in the body and where it is located. Staging describes the severity of an individual's cancer based on the magnitude of the original (primary) tumor as well as on the extent cancer has spread in the body. Understanding the stage of the cancer helps doctors to develop a prognosis and design a treatment plan for individual patients.
Staging provides a common language for doctors to effectively communicate about a patient's cancer and collaborate on the best courses of treatment.
Understanding the cancer's stage is also critical to identifying clinical trials that may be appropriate for particular patients.
Four different types of staging used:
Staging is based on commonly understood knowledge about the way cancer develops and spreads. In most cases, the stage is based on four main factors:
Doctors collect data about a cancer to determine its stage. This information comes from the various tests used to identify staging in different types of cancer.
These tests can include:
The TNM Staging System was developed and is maintained by the AJCC and the Union for International Cancer Control (UICC). It is the most commonly used staging system by medical professionals around the world. The TNM classification system was developed as a tool for doctors to stage different types of cancer based on certain, standardized criteria.
The TNM Staging System includes the extent of the tumor (T), extent of spread to the lymph nodes (N), and presence of metastasis (M).
The T category describes the original (primary) tumor.
Primary tumor cannot be evaluated
No evidence as primary tumor
Carcinoma in situ (early cancer that has not spread to neighboring tissue)
Size and/or extent of the primary tumor
The N category describes whether or not the cancer has reached nearby lymph nodes
Regional lymph nodes cannot be evaluated
No regional lymph node involvement (no cancer found in the lymph nodes)
Involvement of regional lymph nodes (number and/or extent of spread)
The M category tells whether there are distant metastases (spread of cancer to other parts of the body).
No distant metastasis (cancer has not spread to other parts of the body)
Distant metastasis (cancer has spread to distant parts of the body)
Because each cancer type has its own classification system, letters and numbers do not always mean the same thing for every kind of cancer. Once the T, N, and M are determined, they are combined and an overall stage of 0, I, II, III, IV is assigned. Sometimes these stages are subdivided as well, using letters such as IIIA and IIIB.
In some cancer types, non-anatomic factors are required for assigning the anatomic stage/prognostic group. These are clearly defined in each chapter of the AJCC Cancer Staging Manual (e.g., Gleason Score in Prostate). These factors are collected separately from T, N, and M, which remain purely anatomic and are used to assign stage groups.
Where non-anatomic factors are used in groupings, there is a definition of the groupings provided for cases where the non-anatomic factor is not available (X) or where it is desired to assign a group ignoring the non-anatomic factor.
Stage I cancers are the least advanced and often have a better prognosis. Higher stage cancers are often more advanced but in many cases can still be treated successfully.
The formal stage of a cancer does not change over time, even if the cancer progresses. A cancer that returns or spreads is still referred to by the stage it was given when it first diagnosed. In certain cases, after a period of remission a doctor might restage the cancer, but this does not happen very often. If the cancer is restaged, the same process that was done when the cancer was first diagnosed will be repeated: exams, imaging tests, biopsies, and possibly surgery. The new stage will be recorded with a lower case "r" before the restaged designation.