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Stage of Cancer
Once a cancer is diagnosed, it needs to be carefully measured in both its size and extent of spread. This is classified through staging. The main factors affecting the stage of a cancer are the size of the primary tumor (where the cancer started), the involvement of lymph nodes, and the potential spread to other organs in the body. Various cancers are staged differently based on the cancer’s pattern of advancement, how quickly it tends to spread, and where it travels within the body. Staging is commonly done through a physical examination, imaging studies, and sometimes additional biopsies. Staging can be done on various scales, most commonly the TNM staging and a scale of I to IV.
The TNM system is the most common staging system and is used for a wide range of cancers. It is based on factors related to the primary tumor (T category), the extent of involved lymph nodes (N category), and the presence or absence of distant metastasis (M category).
T (tumor size): Larger size or invasion into surrounding tissues is associated with higher T category.
N (nodes): This indicates whether the cancer has spread to the lymph nodes. Larger size of nodes, number of lymph nodes involved, and spread to more distant nodes is associated with higher N category.
M (metastasis): Spread of the cancer to other organs is associated with M1 (metastasis present) vs M0 (no metastasis present).
Why Do We Stage a Cancer?
Staging is performed for several reasons. First, prognosis, which is the likely clinical outcome, is highly associated with the stage of a cancer and gives an opportunity to understand life expectancy and, in some cases, the chance for cure.
Second, recommended treatment for a cancer depends on the stage. Certain therapies (whether surgery, chemotherapy, radiotherapy, or immunotherapy) are indicated for some stages but not others. For example, surgery is routinely recommended for earlier stages of cancer, when the cancer has not spread or has only spread to nearby lymph nodes. In contrast, advanced cancer that has metastasized (spread to distant parts of the body) is commonly treated with systemic medications (such as chemotherapy) that treat disease throughout the entire body.
Finally, clinical trials that test new drugs and management strategies are available to patient populations with a specific cancer and stage. These trials help define new treatment approaches for patient groups defined by cancer and stage.
Example: Staging of Non–Small Cell Lung Cancer
The following is a simplified example of staging on a scale of I to IV. The definitions of each stage will vary between cancers.
Stage I: The cancer is present only in the lung and has not spread to the lymph nodes.
Stage II: The cancer is present in the lung and local lymph nodes (close to the cancer).
Stage III: The cancer is in the lung, local lymph nodes, and lymph nodes more distant from the primary cancer.
Stage IV: The cancer is in both lungs, in the fluid around the lung, or in other body organs.
Cancer Research UKhttps://www.cancerresearchuk.org/about-cancer/what-is-cancer/stages-of-cancer
Published Online: June 11, 2020. doi:10.1001/jamaoncol.2020.1592
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Patel A, West H. What Does My Stage of Cancer Mean? JAMA Oncol. 2020;6(8):1308. doi:10.1001/jamaoncol.2020.1592
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