The fact that you have a serious illness is never welcome news. But, receiving a cancer diagnosis may be one of the most disconcerting experiences for a patient and their family. Helping them understand what they are facing is one of the reasons that cancer “staging systems” were developed. In addition to giving a person a sense of how serious their cancer is, cancer stages are also used to devise the most effective treatment and to identify clinical trials that may be useful.
It is important to note that a cancer is always referred to by the stage it was given when first detected. Details on how the cancer has changed or spread get added on to the original stage, but that stage remains the same. For example, a stage III breast cancer that is no longer detectable after treatment but later returns and is found elsewhere is now referred to as “stage III breast cancer, with recurrent disease in [the organ or area].”
Not all cancers are referred to by stages. For example, most cases of leukemia, which are cancers of the blood cells and therefore exist throughout the body, are not assigned stages or are staged differently than other kinds of cancers.
Different Systems for Cancer Stages
While the same kinds of assessments—x-rays, lab tests, etc.—are used to evaluate most kinds of cancer, there are different systems for describing the results. One of the most common is the TNM system. In it, letters and numbers are used to describe a cancer:
- T represents the original/primary tumor.
- N stands for “nodes” and indicates the degree of spread to nearby lymph nodes.
- M stands for “metastasis” and tells whether the cancer has spread to distant areas of the body.
Numbers are then used to quantify the size of the tumor, the number of lymph nodes involved or the degree of spread, with higher numbers indicating a more serious condition. The letter “X” is applied when no measurement can be taken.
In some systems, the TNM results are distilled down into five simpler numeric stages:
- Stage 0 – Abnormal cells are present, but they are not technically cancer.
- Stages I-III – Cancer is present. The higher the number, the larger the tumor and the more the cancer has spread into nearby tissues.
- Stage IV – Cancer is present and has spread to distant parts of the body.
Another staging system uses five descriptors:
- In situ – Abnormal cells are present, but there is no spread to nearby tissue.
- Localized – Cancer is present, but it has not spread from the site where it originated.
- Regional – Cancer is present and has spread to nearby tissues, lymph nodes or organs.
- Distant – Cancer is present and has spread to distant parts of the body.
- Unknown – Not enough information is available to determine a stage.
If you or a loved one is diagnosed with cancer, your care team will explain the system that will be used to classify it and the stage it has been assigned. This will help everyone involved understand the condition as a treatment plan is created and put into action.