Tumour stage
Cancer staging is the process of determining the extent to which a cancer has developed by spreading. Contemporary practice is to assign a number from I to IV to a cancer, with I being an isolated cancer and IV being a cancer which has spread to the limit of what the assessment measures. The stage generally takes into account the size of a tumor, whether it has invaded adjacent organs, how many regional (nearby) lymph nodes it has spread to (if any), and whether it has appeared in more distant locations (metastasized).
The most clinically useful staging system is the tumor, node, and metastasis (TNM) staging system developed by the American Joint Committee on Cancer (AJCC) in collaboration with the Union for International Cancer Control (UICC), herein referred to as the AJCC TNM staging system. The AJCC TNM system classifies cancers by the size and extent of the primary tumor (T), involvement of regional lymph nodes (N), and the presence or absence of distant metastases (M), supplemented in recent years by evidence-based prognostic and predictive factors. There is a TNM staging algorithm for cancers of virtually every anatomic site and histology, with the primary exception of pediatric cancers.
The AJCC and UICC periodically modify the AJCC TNM staging system in response to newly acquired clinical and pathological data and an improved understanding of cancer biology and other factors affecting prognosis. Periodic and, to the extent possible, evidence-based revision is a key feature that makes this staging system the most clinically useful among staging systems and accounts for its widespread use worldwide. However, because changes in staging systems may make it difficult to compare outcomes of patients over time, evidence-based changes to this staging system are made with deliberate care.
In general, the revision cycle for AJCC TNM staging has historically been 5 to 7 years. This approach provides sufficient time for implementation of changes in clinical management and cancer registry operations and for relevant examination and discussion of data supporting changes in staging. Table 1.1 shows the publication year for each version of the AJCC TNM system up through this current AJCC Cancer Staging Manual, 8th Edition. The AJCC Cancer Staging Manual, 7th Edition was used for cancer patients diagnosed on or after January 1, 2010. The 8th Edition published in this manual is effective for cancer patients diagnosed on or after January 1, 2018. The AJCC recognizes that rapidly evolving evidence may necessitate more frequent updates of AJCC TNM staging in the future, and anticipates providing more frequent updates for disease sites as new and validated evidence becomes available. Moreover, the AJCC also recognizes that as clinical cancer care continues to evolve and incorporates factors that are not used to determine stage but that provide key information on specific outcomes and/or expected benefit from specific therapies, new, validated clinical tools will be needed to help clinicians efficiently and accurately use these important data to enhance clinical care (see Anatomic Staging and the Evolving Use of Nonanatomic Factors).
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