Stage 3 stomach cancer is an advanced form of the disease. It means that the primary tumor has spread beyond the walls of the stomach to nearby lymph nodes but not to other distant sites.

Symptoms may include abdominal pain, bloody stool, unintentional weight loss, and jaundice.

Although the outlook for someone with stage 3 stomach cancer varies, doctors can still treat it effectively. Treatment typically involves surgery to remove part or all of the stomach and chemotherapy to remove any remaining cancer cells.

This article explores stage 3 stomach cancer, including its symptoms, treatment, and outlook.

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Cancer staging determines how advanced a cancerous tumor is and how far it has spread.

Because cancer is unpredictable and can affect people differently, doctors perform a series of tests and exams to help them assign a stage to a tumor. The staging system helps guide the doctor’s treatment decisions and determines the person’s prognosis.

There are several staging systems, but doctors typically use the American Joint Committee on Cancer TNM system for stomach cancer. The TNM system considers three factors:

  • Tumor (T): This category describes the extent of the primary tumor, including how far it has grown into the stomach wall tissue and if it has reached nearby structures or organs.
  • Nodes (N): This describes whether or not the cancer has spread to nearby lymph nodes.
  • Metastases (M): This describes any spread of the disease to distant organs, such as the liver or lungs.

Each classification has a score according to the disease’s severity. A doctor then considers these scores to assign a cancer stage that indicates how advanced it is.

Stage 3 stomach cancer has grown into or through the outer lining of the stomach and has also spread to nearby lymph nodes. However, it has not spread to other organs or distant body parts.

Doctors further divide stage 3 stomach cancer into categories A, B, and C.

Stage 3A stomach cancer

In 3A stomach cancer, the cancer has spread to one of these sets of areas:

  • the muscle layer of the stomach wall and 7–15 nearby lymph nodes
  • the subserosa — the connective tissue layer that lies next to the muscle layer — of the stomach wall and 3–6 nearby lymph nodes
  • the serosa, or outer layer of the stomach wall, and 1–6 nearby lymph nodes
  • nearby organs, such as the spleen, colon, liver, or the back of the abdomen

Stage 3B stomach cancer

In 3B stomach cancer, cancer has spread to one of these sets of areas:

  • the submucosa, or the muscle layer of the stomach wall, and 16 or more nearby lymph nodes
  • the subserosa or the serosa of the stomach wall and 7–15 nearby lymph nodes
  • nearby organs and 1–6 nearby lymph nodes

Stage 3C stomach cancer

In 3C stomach cancer, cancer has spread to one of these sets of areas:

  • the subserosa or the serosa of the stomach wall and 16 or more nearby lymph nodes
  • nearby organs and seven or more nearby lymph nodes

In the more advanced stages of stomach cancer, people may experience the following symptoms:

  • blood in the stool
  • vomiting
  • unexplained weight loss
  • stomach pain
  • yellowing of eyes and skin, or jaundice
  • a buildup of fluid in the abdomen, or ascites
  • difficulty swallowing

Doctors may find it difficult to estimate the progression of stage 3 stomach cancer. Certain factors, such as the type of cancer, the location of the tumor, and a person’s overall health and age, can affect it.

Some types of stomach cancer, such as diffuse stomach cancer, are particularly aggressive and challenging for doctors to diagnose. Therefore, they may progress more quickly than other forms, such as adenocarcinoma.

Depending on the location and extent of the stomach cancer, doctors may suggest surgery as the first treatment. This involves removing part or all of the stomach, nearby lymph nodes, and possibly parts of nearby organs.

Another option is chemotherapy, which doctors may use alone or in combination with radiation therapy. The aim is to shrink the tumor, making surgery easier.

The outlook for stage 3 stomach cancer varies. Around 3 in 10 people with regional cancer that has spread outside the stomach to nearby structures or lymph nodes are alive 5 years after diagnosis.

However, it is important to note that a person’s outlook also depends on many factors, such as age and overall health. Doctors can often help people with stage 3 stomach cancer live longer with modern and emerging treatments.

Stage 3 stomach cancer is an advanced form of the disease where the tumor has grown through the stomach wall and spread to nearby lymph nodes. It has not yet spread to other organs or distant body parts.

Treatment options vary depending on the location and stage of cancer but may include surgery and chemotherapy.

Although the outlook for stage 3 stomach cancer is generally unfavorable, many treatments are available to help those living with the condition live longer.