An important part of treating a patient’s cancer is to first find out how far it has spread, or what “stage” it has reached.

“We want to know: Where is the cancer? Has it spread from where it originated in the body? And if it has spread, to what degree?” says Willamette Valley Cancer Institute oncologist Dr. Wayne Ormsby.

Knowing the stage helps doctors plan the appropriate type of treatment, estimate a patient’s prognosis and identify clinical trials that may be suitable.

How is staging determined?
The TNM system is one of the most widely used cancer staging systems. It is mainly used to describe cancers that form solid tumors, including breast, colon and lung cancers. This system examines:

•    The size and extent of the primary tumor (T)
•    Whether the cancer has spread to nearby lymph nodes (N)
•    Whether the cancer has spread (metastasized) to other parts of the body. (M)

Doctors determine the stage of a cancer by combining the T, N and M classifications.
Most cancers have four stages. Some cancers also have a stage 0 (zero):

What do the stages mean?
Stage 0: This is used to describe cancer in situ, which means the cancer is still located where it started and has not invaded nearby tissues.

Stage I: This is usually a small cancer or tumor that has not grown deeply into nearby tissues and has not spread to the lymph nodes or other parts of the body. It is often called early-stage cancer.

Stage II and III: Cancer or tumors that are larger in size, have grown more deeply into nearby tissue, and have spread to lymph nodes, but not to other parts of the body.

Stage IV: The cancer has spread to other organs or parts of the body. It may also be called advanced or metastatic cancer.

Dr. Ormsby says it’s important to recognize that staging varies based on the type of cancer and the individual patient.

“Stage IV breast cancer is not the same as stage IV lymphoma or stage IV head and neck cancer,” he says. “The prognosis and treatment is going to be very different in each of these situations.”

Cancers of the blood, including leukemia, lymphoma and multiple myeloma use a different staging system, since they do not form solid tumors. To learn more about staging for each cancer type, click here.