What does the stage of a cancer mean?

The stage of a cancer refers to its extent, such as how large the tumor is and whether it has spread. According to the National Cancer Institute, knowing the stage helps a doctor understand how serious the cancer is and a person's chances of survival, plan the best treatment, and identify clinical trials that may be options.

Most staging systems include information about where the tumor is located, the size of the tumor, whether the cancer has spread to nearby lymph nodes, and whether it has spread to a different part of the body.

Many cancers are grouped into stages 0 through 4. Stage 0 means abnormal cells are present but have not spread (also called carcinoma in situ). Stages I, II, and III mean cancer is present, with higher numbers meaning a larger tumor and more spread into nearby tissues. Stage IV means the cancer has spread to distant parts of the body.

One important point: a cancer is always referred to by the stage it was given at diagnosis, even if it later gets worse or spreads. A healthcare team can explain what a specific stage means and how it affects treatment options.