Staging

Staging is a way of describing a cancer, such as where it is located, if or where it has spread, and if it is affecting the functions of other organs in the body. Doctors use diagnostic tests to determine the cancer's stage, so staging may not be complete until all of the tests are finished. Knowing the stage helps the doctor to decide what kind of treatment is best and can help predict a patient's prognosis (chance of recovery). There are different stage descriptions for different types of cancer.

One tool that doctors use to describe the stage is the TNM system. This system uses three criteria to judge the stage of the cancer: the tumor itself, the lymph nodes around the tumor, and if the tumor has spread to the rest of the body. The results are combined to determine the stage of cancer for each person. There are five stages: stage 0 (zero) and stages I through IV (one through four). The stage provides a common way of describing the cancer, so doctors can work together to plan the best treatments.

TNM is an abbreviation for tumor (T), node (N), and metastasis (M). Doctors look at these three factors to determine the stage of cancer:

• How large is the primary tumor and where is it located? (Tumor, T)
• Has the tumor spread to the lymph nodes? (Node, N)
• Has the cancer metastasized to other parts of the body? (Metastasis, M)

Tumor. Using the TNM system, the “T” plus a letter or number (0 to 4) is used to describe the size and location of the tumor. Some stages are also divided into smaller groups that help describe the tumor in even more detail. Specific tumor stage information is listed below:

• TX: The primary tumor cannot be evaluated.
• T0 (T plus zero): There is no evidence of a primary tumor in the stomach.
• Tis: This stage describes a condition called carcinoma (cancer) in situ. The cancer is found only in cells on the surface of the epithelium (the inner lining of the stomach) and has not spread to any other layers of the stomach.
• T1: The tumor has invaded the lamina propria and the submucosa (the inner layers of the wall of the stomach).
• T2: The tumor has invaded the muscularis propria (the muscle layer of the stomach) and the subserosa (the outer muscle layers of the stomach).
• T2a: The tumor has grown through the muscularis propria.
• T2b: The tumor has grown into the serosa (the outer layer of the stomach).
• T3: The tumor has grown through the serosa, but the tumor has not invaded structures or organs outside the stomach.
• T4: The tumor has invaded structures or organs surrounding the stomach, such as the spleen, colon, or liver.
  

Node. The “N” in the TNM staging system is for lymph nodes, the tiny, bean-shaped organs that help fight infection. Lymph nodes inside the abdomen are called regional lymph nodes. Lymph nodes in other parts of the body are called distant lymph nodes. The overall prognosis for patients with stomach cancer is based on how many regional lymph nodes show evidence of cancer. If six lymph nodes or less are involved, the prognosis is better than if more than 15 lymph nodes contain cancer cells.

• NX: Regional lymph nodes cannot be evaluated.
• N0 (N plus zero): The cancer has not spread into the regional lymph nodes.
• N1: The cancer has spread to one to six regional lymph nodes.
• N2: The cancer has spread to seven to 15 regional lymph nodes.
• N3: The cancer has spread to more than 15 regional lymph nodes.

Distant metastasis. The “M” in the TNM system indicates whether the cancer has spread to other parts of the body.

• MX: Distant metastasis cannot be evaluated.
• M0 (M plus zero): The cancer has not metastasized.
• M1: The cancer has spread to another part or parts of the body.

Cancer stage grouping

Doctors assign the stage of the cancer by combining the T, N, and M classifications.

Stage 0: This is also called carcinoma in situ. The cancer is found only on the surface of the epithelium. The cancer has not invaded any other layers of the stomach and is considered an early cancer (Tis, N0, M0).

Stage Ia: The cancer has invaded the inner layer of the wall of the stomach, but the cancer has not spread to any lymph nodes or other organs (T1, N0, M0).

Stage Ib: Stomach cancer is called stage IB in either of these two conditions:

• The cancer has grown into the inner layers of the wall of the stomach and has spread to one to six lymph nodes, but not elsewhere (T1, N1, M0).
• The cancer has grown into outer muscular layers of the wall of the stomach, but the cancer has not spread to the lymph nodes or other organs (T2a or T2b, N0, M0).

Stage II: Stomach cancer is called stage II in any one of these conditions:

• The cancer has invaded the inner layer of the wall of the stomach and has spread to seven to 15 lymph nodes, but not elsewhere (T1, N2, M0).
• The cancer has invaded the outer muscular layers of the wall of the stomach and has spread to one to six lymph nodes, but not elsewhere (T2a or T2b, N1, M0).
• The cancer has grown through the wall of the stomach, but it has not spread to any lymph nodes or surrounding organs (T3, N0, M0).

Stage IIIa: Stomach cancer is called stage IIIA in any one of these conditions:

• The cancer has invaded the outer muscular walls of the stomach and has spread to seven to 15 lymph nodes, but not to other organs (T2a or T2b, N2, M0).
• The cancer has grown through the wall of the stomach and has spread to one to six lymph nodes, but not to other organs (T3, N1, M0).
• The cancer has invaded organs or structures surrounding the stomach, but the cancer has not spread into any lymph nodes or other organs (T4, N0, M0).

Stage IIIb: Stomach cancer has grown through the wall of the stomach but has not invaded any surrounding organs. The cancer has spread to seven to 15 lymph nodes (T3, N2, M0).

Stage IV: Stomach cancer is called stage IV in any of these conditions:

• Any distant metastasis to other parts of the body besides the area around the stomach (any T, any N, M1).
• The cancer has invaded more than 15 lymph nodes, regardless of how deeply the tumor has invaded the wall of the stomach (any T, N3, M0).
• The cancer has invaded the structures or organs surrounding the stomach and has spread to the lymph nodes (T4, N1 to N3, M0).

Recurrent cancer. Recurrent cancer is cancer that comes back after treatment. It may be a localized recurrence (comes back in the place where it started), or it may be a distant metastasis (comes back in another part of the body).

Used with permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original source for this material is the AJCC Cancer Staging Manual, Sixth Edition (2002) published by Springer-Verlag New York, www.springer-ny.com.

The Japanese system for staging stomach cancer

Stomach cancer is much more common in Japan (and other parts of Asia and South America) than in the United States. The Japanese have a different method of staging stomach cancer, based on where the affected lymph nodes are located around the stomach. This is different from the U.S. system, which uses the number of nodes and not their location.

Surgery for stomach cancer may be described using the Japanese system. The type of surgery is identified by which lymph nodes are removed in addition to the stomach.

• D0: no lymph nodes were removed
• D1: the lymph nodes closest to the stomach were removed
• D2: lymph nodes from a wider area were removed