A cancer diagnosis typically comes with a determination of the cancer’s stage.
Cancer staging systems provide common language and criteria so that doctors can work together to determine the best course of treatment.
Each type of cancer has its own prognosis and path of development, but generally, the stage indicates the size of the tumor and how much it has spread to other tissues.
There are two main types of staging systems: the TNM and the number systems.
The TNM System
TNM stands for:
Each letter category is assigned a number, which allows a more specific description of the cancer.
How Large is the Primary Tumor?
- TX – unknown or cannot be measured
- T0 – no evidence of a tumor
- Tis (in situ) – the tumor has not spread to any surrounding tissue (“in situ” means “in its original place”)
- T1, T2, T3, T4 – the size of the tumor on a scale of 1 to 4 (and how much it has grown into nearby tissues)
Has the Tumor Spread to the Lymph Nodes?
- NX – unknown or inaccessible
- N0 – no cancer found in nearby lymph nodes
- N1, N2, N3 – location, size, or number of nodes found with cancer cells
Has the Cancer Spread to Other Parts of the Body?
- M0 – no apparent spread.
- M1 – cancer has spread to distant parts of the body.
The Numbered Staging System
With that information about the tumor size and its spread, the healthcare team can then assign an overall stage to the cancer.
The stages are numbered from 0 to 4, with 0 being the earliest stage and four being the most advanced.
- Stage 0 – cancer in situ (“in place”), still located where it started without any evident spreading; often the most curable, typically through surgical removal
- Stage 1 – cancer has not yet grown deeply into nearby tissues and has not spread to the lymph nodes or other parts of the body; often called “early-stage cancer”
- Stage 2 – cancer has grown or is pushing into surrounding tissues; local spread
- Stage 3 – cancer is larger and spreading regionally or into the lymphatic system
- Stage 4 – cancer has spread to other organs or parts of the body; often called “advanced” or “metastatic” cancer.
Some types of cancer are not given a staging designation because they don’t tend to grow and spread in the same way as other types of cancer.
For example, leukemia is described as either acute or chronic. And brain cancers don’t often spread outside of the brain, so staging may be unnecessary.
Staging and Treatment Plans
Cancer staging is essential so that doctors can develop the best treatment plan for each individual patient.
Categorizing the cancer by stage helps researchers compare cancer patients in clinical trials and study outcomes.
Cancer staging can also help doctors estimate a patient’s prognosis. The stage at diagnosis is one of the most important factors in predicting the outcomes of many types of cancer.
However, even with all this information, it’s important to remember that cancer is complex and that each person responds differently to a treatment.
Overall, the staging system is an important communication tool that can help you and your healthcare team make the best decisions about your individual care.