Stages of Stomach Cancer

Staging is the process of describing where a cancer is located and how far it has spread to other parts of the body, if at all. This determines the severity and extent of your cancer, which helps doctors predict the course of your condition (prognosis) and decide on the best treatment options for you. For instance, early-stage stomach (gastric) cancer may be treated with surgery only, while more advanced gastric cancer would likely require a combination of treatments, such as surgery and chemotherapy.

When your doctor first suspects that you may have gastric cancer, they will order a series of diagnostic tests to confirm whether you have the condition. These tests will give some information to estimate the stage of your cancer. This includes the size of the tumor, whether regional lymph nodes are involved and if there is any distant spread.

While cancer is typically staged when it is first diagnosed and before any treatment, in some cases, it can be staged again over the course of your treatment journey. The cancer is first assigned a clinical stage based on the results of initial tests, such as imaging scans and endoscopies, that are done before treatment begins. The clinical stage is generally used to plan the best treatment options and establish your prognosis.

If surgery is done to remove the gastric tumor, doctors can also determine the cancer’s pathological stage. This is derived from the results of earlier tests as well as those from the surgery. The pathological stage often gives more precise information about the cancer, which makes it a much more accurate indicator of its actual progression within the body. In some instances, the pathological stage can be different from the clinical stage. An example would be if the cancer is revealed during surgery to have spread to regional lymph nodes that may not be evident on imaging tests.

Some cancer patients may receive other types of treatment, such as chemotherapy or radiation therapy, before surgery. This is known as neoadjuvant therapy, which is done in selected cases to reduce the size of the gastric tumor so that there is a higher chance of successfully removing it from the body. Tests may be repeated after neoadjuvant therapy to assess the cancer’s response to treatment.

Doctors use classification systems to determine the stage of cancers. Most commonly used for gastric cancer is the TNM staging system designed by the American Joint Committee on Cancer (AJCC). TNM is an acronym for tumor (T), nodes (N) and metastasis (M), which are also the three broad categories of this system.

The TNM system uses different stage descriptions for different types of cancer. This means that each cancer type has its own version of the TNM categories. Therefore, gastric adenocarcinomas are staged differently from other types of gastric cancer, such as gastrointestinal stromal tumors (GISTs) and lymphomas. Adenocarcinomas arise from the epithelial cells of the mucosa layer within the stomach wall. Staging is also different for proximal gastric cancers that extend into the gastroesophageal junction; these are often staged and treated as esophageal cancers. The following covers the staging of adenocarcinomas, which account for almost 95% of all cancers of the stomach.

Tumor (T)

The T category describes the depth of invasion of the main (primary) tumor, this includes whether it has invaded nearby structures and organs. Stages in this category are assigned a letter or number (0 to 4). The higher the number after the T, the more it has grown into nearby tissues.

TX means the primary tumor cannot be assessed due to lack of information.

T0 means there is no evidence of a primary tumor in the stomach.

This means that the tumor is still confined to the epithelial cells of the mucosa, where they first started, and are not growing into deeper layers.

T1 means the tumor has started to grow into the inner layers of the stomach wall. It can be further divided into two subcategories: T1a and T1b.

• T1a means the tumor has grown into the connective tissue layer (lamina propria) or muscle layer (muscularis mucosae) of the mucosa.
• T1b means the tumor has grown through the mucosa and into the submucosa.

T2 means the tumor has grown into the muscularis propria, the thick muscle layer of the stomach.

T3 means the tumor has grown through all muscle layers and into the layer of connective tissue outside the stomach known as the subserosa. It has not grown into the lining of the abdomen, known as the peritoneal lining, or into the serosa, which is the outermost layer of the stomach wall.

T4 means the tumor has grown through all muscle layers and into the subserosa. It has also grown into the peritoneal lining, serosa or surrounding organs. It is divided into two subcategories: T4a and T4b.

• T4a means the tumor has grown into the peritoneal lining and serosa, but not into surrounding organs.
• T4b means the tumor has grown through the peritoneal lining and serosa and into organs surrounding the stomach, such as the liver or pancreas.

Nodes (N)

The N category describes any cancer spread to lymph nodes near the stomach. Lymph nodes are small, bean-shaped structures that form a network throughout the body. They drain away waste products and damaged cells and contain lymphocytes that fight infection and disease. Cancers often spread from the primary tumor to surrounding lymph nodes before they reach other parts of the body. Stages in the N category are also assigned a number and letter. The higher the number after the N, the greater the spread of the cancer to nearby lymph nodes.

NX means nearby lymph nodes cannot be assessed due to a lack of information.

N0 means the cancer has not spread to any nearby lymph nodes.

N1 means the cancer has spread to 1 to 2 nearby lymph nodes.

N2 means the cancer has spread to 3 to 6 nearby lymph nodes.

N3 means the cancer has spread to 7 or more nearby lymph nodes. It is split into two subcategories: N3a and N3b.

• N3a means the cancer has spread to 7 to 15 nearby lymph nodes.
• N3b means the cancer has spread to 16 or more nearby lymph nodes.

Metastasis (M)

The M category describes any cancer spread to distant parts of the body, such as the liver or lungs. This is known as metastasis. There are three stages in this category.

MX means that distant metastasis cannot be evaluated due to a lack of information.

M0 means that the cancer has not spread to distant parts of the body.

M1 means that the cancer has spread to distant organs or tissues.

To show if the staging is a clinical or pathological classification, each of the T, N and M categories might have a lowercase letter written in front of it. A clinical stage is noted with “c” (e.g. cT1), while a pathological stage is noted with “p” (e.g. pT2). Gastric cancers that are staged after neoadjuvant therapy are noted with a “y” in front of the category (e.g. ycT1).

Once the gastric cancer’s T, N and M categories have been determined, this information is combined in a process called stage grouping to assign an overall stage. There are five stages for gastric cancer— stage 0, followed by stages I (1) through IV (4). Some stages have subdivisions as well, such as stages IIIA and IIIB.

Stage 0

Also called carcinoma in situ (in its original place), the cancer is found only in the epithelial cells of the mucosa, where it first started, and has not grown into the deeper layers of the stomach wall. These are considered pre- or early-stage gastric cancers (TNM: Tis, N0, M0).

Stage I

Stage I gastric cancers are divided into stages IA and IB.

• Stage IA: The cancer has grown into the inner layers of the stomach wall (the lamina propria, muscularis mucosae or submucosa). It has not spread to any nearby lymph nodes or other organs (TNM: T1, N0, M0).
• Stage IB: The cancer has either
  • grown into the inner layers of the stomach wall (the lamina propria, muscularis mucosae or submucosa) and spread to 1 to 2 lymph nodes, but not to other organs (TNM: T1, N1, M0), or
  • grown into the muscularis propria but has not spread to any nearby lymph nodes or other organs (TNM: T2, N0, M0).

Stage II

Stage II gastric cancers are divided into stages IIA and IIB.

• Stage IIA: The cancer has either
  • grown into the inner layers of the stomach wall (the lamina propria, muscularis mucosae or submucosa) and spread to 3 to 6 lymph nodes, but not to other organs (TNM: T1, N2, M0),
  • grown into the muscularis propria and spread to 1 to 2 lymph nodes, but not to other organs (TNM: T2, N1, M0), or
  • grown through all of the muscle layers and into the subserosa. It has not grown into the peritoneal lining, the serosa or spread to any nearby lymph nodes or other organs (TNM: T3, N0, M0).
• Stage IIB: The cancer has either
  • grown into the inner layers of the stomach wall (the lamina propria, muscularis mucosae or submucosa) and spread to 7 to 15 lymph nodes, but not to other organs (TNM: T1, N3a, M0),
  • grown into the muscularis propria and spread to 3 to 6 lymph nodes, but not to other organs (TNM: T2, N2, M0),
  • grown through all of the muscle layers and into the subserosa. It has not grown into the peritoneal lining or serosa. It has spread to 1 to 2 nearby lymph nodes but not to other organs (TNM: T3, N1, M0), or
  • grown through all of the muscle layers and into the subserosa. It has also grown into the peritoneal lining or serosa, but has not spread to any nearby lymph nodes or other organs (TNM: T4a, N0, M0).

Stage III

Stage III gastric cancers are divided into stages IIIA, IIIB and IIIC.

• Stage IIIA: The cancer has either
  • grown into the muscularis propria and spread to 7 to 15 lymph nodes, but not to other organs (TNM: T2, N3a, M0),
  • grown through all of the muscle layers and into the subserosa. It has not grown into the peritoneal lining or serosa. It has spread to 3 to 6 nearby lymph nodes but not to other organs (TNM: T3, N2, M0),
  • grown through all of the muscle layers and into the subserosa. It has also grown into the peritoneal lining or serosa and spread to 1 to 2 lymph nodes, but not to other organs (TNM: T4a, N1, M0), or
  • grown through all of the muscle layers and into the subserosa. It has also grown into the peritoneal lining and serosa and into organs surrounding the stomach. It has not spread to nearby lymph nodes or distant organs (TNM: T4b, N0, M0).
• Stage IIIB: The cancer has either
  • grown into the inner layers of the stomach wall (the lamina propria, muscularis mucosae or submucosa) and spread to 16 or more lymph nodes, but not to other organs (TNM: T1, N3b, M0),
  • grown into the muscularis propria and spread to 16 or more lymph nodes, but not to other organs (TNM: T2, N3b, M0),
  • grown through all of the muscle layers and into the subserosa. It has not grown into the peritoneal lining or serosa. It has spread to 7 to 15 nearby lymph nodes but not to other organs (TNM: T3, N3a, M0),
  • grown through all of the muscle layers and into the subserosa. It has also grown into the peritoneal lining or serosa and spread to 7 to 15 nearby lymph nodes but not to other organs (TNM: T4a, N3a, M0),
  • grown through all of the muscle layers and into the subserosa. It has also grown into the peritoneal lining and serosa and into organs surrounding the stomach. It has spread to 1 to 2 nearby lymph nodes but not to distant organs (TNM: T4b, N1, M0), or
  • grown through all of the muscle layers and into the subserosa. It has also grown into the peritoneal lining and serosa and into organs surrounding the stomach. It has spread to 3 to 6 nearby lymph nodes but not to distant organs (TNM: T4b, N2, M0).
• Stage IIIC: The cancer has either
  • grown through all of the muscle layers and into the subserosa. It has not grown into the peritoneal lining or serosa. It has spread to 16 or more nearby lymph nodes but not to other organs (TNM: T3, N3b, M0),
  • grown through all of the muscle layers and into the subserosa. It has also grown into the peritoneal lining or serosa and spread to 16 or more nearby lymph nodes but not to other organs (TNM: T4a, N3b, M0),
  • grown through all of the muscle layers and into the subserosa. It has also grown into the peritoneal lining and serosa and into organs surrounding the stomach. It has spread to 7 to 15 nearby lymph nodes but not to distant organs (TNM: T4b, N3a, M0), or
  • grown through all of the muscle layers and into the subserosa. It has also grown into the peritoneal lining and serosa and into organs surrounding the stomach. It has spread to 16 or more nearby lymph nodes but not to distant organs (TNM: T4b, N3a, M0).

Stage IV

In this stage, the cancer may or may not have grown into any of the layers of the stomach wall and it might or might not have spread to nearby lymph nodes. However, it has spread to areas beyond the stomach and to distant organs in the body (TNM: any T, any N, M1). This is known as metastatic gastric cancer.

The higher the number of the stage, the more the cancer has spread. Early-stage gastric cancers usually have a better prognosis. Meanwhile, higher-stage cancers of the stomach have generally spread more extensively, have poorer prognosis and might require different kinds of treatment. If you have been diagnosed with gastric cancer, understanding your cancer stage can help you better comprehend the severity of your condition, the treatment options available and their outcomes. By having a better understanding of your cancer stage, you can make more informed decisions and ask relevant questions to your cancer care team. This will help you stay on top of things as you navigate through this challenging journey. So don’t hesitate to communicate any concerns or doubts you may have.