Introduction: Who Should Undergo Diagnostics

If you are experiencing ongoing symptoms such as persistent indigestion, heartburn, abdominal bloating, nausea, loss of appetite, blood in the stool or vomit, unexplained weight loss, abdominal pain, jaundice, or difficulty swallowing, it is important to speak with a doctor.^[1][4] These symptoms could indicate stomach cancer or another serious condition that requires professional evaluation.

Stomach cancer tends to develop slowly over many years, and because early-stage disease often has subtle or no symptoms, many people are diagnosed only when the cancer has already reached an advanced stage.^[1][2] In fact, early-stage disease accounts for only 10% to 20% of all stomach cancer cases diagnosed in the United States.^[10] This makes it especially important to seek medical advice if you notice symptoms that persist or worsen.

You should consider diagnostic testing if you have risk factors such as advanced age, a family history of stomach cancer, previous stomach problems like chronic atrophic gastritis or pernicious anemia, infection with Helicobacter pylori (a type of bacteria that infects the stomach lining), or a diet high in salted or preserved foods.^[1][10] Men and older adults are at slightly higher risk, and the average age of people diagnosed with stomach cancer is 68.^[1]

When cancer has already been diagnosed and treated, follow-up diagnostics may be needed to check if the cancer has returned or spread to other parts of the body. This is especially true if you develop new symptoms after treatment has been completed.^[2]

Diagnostic Methods for Identifying Metastatic Gastric Cancer

Doctors use a series of tests and procedures to diagnose metastatic gastric cancer and to understand where the cancer has spread. The process usually begins with a detailed review of your medical history and a physical examination. During the physical exam, the doctor will feel your abdomen for any masses or unusual lumps and check for signs such as jaundice, which can indicate that the cancer has spread to the liver.^[4][5]

Blood Tests

Blood tests are commonly ordered to assess your general health and detect signs of disease. A complete blood count can reveal anemia, which might suggest internal bleeding from the stomach. Other blood tests may check liver function or other organ function to see if the cancer has affected them.^[4]

Upper Endoscopy

An upper endoscopy, also called esophagogastroduodenoscopy or EGD, is one of the most important diagnostic procedures for stomach cancer. During this test, a thin, flexible tube with a camera on the end is passed through your mouth, down your throat, and into your stomach. The doctor can see the inside of the stomach and look for any abnormal areas. If something suspicious is found, small tissue samples, called biopsies, can be taken during the same procedure.^[5]

The biopsy samples are then sent to a laboratory where they are examined under a microscope to check for cancer cells. This is the main way doctors confirm whether you have stomach cancer and what type it is.^[5]

Barium Swallow Test

A barium swallow, also known as an upper gastrointestinal series, involves swallowing a liquid containing barium, which coats the lining of the esophagus and stomach. X-rays are then taken, and the barium makes any abnormal areas easier to see. This test can help doctors identify tumors or blockages in the stomach.^[4]

Imaging Tests

Once stomach cancer is confirmed, imaging tests are used to find out if and where the cancer has spread. These tests create detailed pictures of the inside of your body and are essential for staging the cancer—that is, determining how advanced it is.^[7]

Computed tomography (CT) scans use X-rays taken from many angles to create cross-sectional images of your body. CT scans are very helpful for seeing whether the cancer has spread to the liver, lungs, lymph nodes, or the tissue lining the abdominal cavity, called the peritoneum.^[4][5]

Positron emission tomography (PET) scans involve injecting a small amount of radioactive sugar into your bloodstream. Cancer cells absorb more of this sugar than normal cells, so they light up on the scan. PET scans can help detect cancer that has spread to distant parts of the body.^[4]

Other imaging tests such as ultrasound or MRI scans may also be used depending on your specific situation. For example, an abdominal ultrasound can help evaluate the liver and other organs for signs of metastasis.^[4]

Understanding Where Stomach Cancer Spreads

Metastatic stomach cancer, also called stage 4 stomach cancer, means the cancer has spread beyond the stomach to at least one other part of the body.^[2][4] The most common places where stomach cancer spreads are the liver, the peritoneum, the lungs, and the bones.^[3]

According to research, among patients with metastatic gastric cancer, about 48% have cancer that has spread to the liver, 32% to the peritoneum, 15% to the lungs, and 12% to the bones.^[3] The pattern of spread can differ depending on the location of the original tumor in the stomach and the type of cancer cells. For example, cancer in the upper part of the stomach, near where it connects to the esophagus (called the cardia), tends to spread more often to the lungs, nervous system, and bones. In contrast, cancer in the lower part of the stomach (non-cardia) more commonly spreads within the peritoneum.^[3]

The symptoms you experience can depend on where the cancer has spread. If it has reached the liver, you might develop jaundice, where your skin and eyes turn yellow. If it has spread to the bones, you might have bone pain or fractures. Cancer in the lungs could cause breathing problems or coughing. Cancer affecting the bowels or bladder might lead to blood in the urine or stool, or pain during urination or bowel movements.^[4]

Staging the Cancer

After all the diagnostic tests are completed, doctors assign a stage to the cancer. Staging describes how much cancer is in the body, how large the tumor is, and how far it has spread.^[7] Metastatic gastric cancer is classified as stage 4, the most advanced stage. Stage 4 means that the cancer has spread to distant organs or tissues, such as the liver, lungs, or distant lymph nodes.^[2][7]

Doctors may also use a system called TNM staging, which stands for tumor, node, and metastasis. This system describes the size of the tumor (T), whether it has spread to nearby lymph nodes (N), and whether it has spread to distant parts of the body (M). When the “M” is 1, it means metastasis is present.^[7]

Diagnostics for Clinical Trial Qualification

If you are interested in participating in a clinical trial—a research study that tests new treatments—you will need to undergo specific diagnostic tests to see if you qualify. Clinical trials have strict rules about who can join, and these rules are based on the characteristics of your cancer and your overall health.^[5]

Doctors will typically perform tests to confirm the stage of your cancer and to identify certain biological markers, also called biomarkers, in your cancer cells. Biomarkers are specific molecules or features of the cancer that help doctors predict how the cancer will behave and which treatments might work best.^[8]

Biomarker Testing

One of the most important biomarkers for metastatic gastric cancer is HER2, which stands for human epidermal growth factor receptor 2. HER2 is a protein that helps cancer cells grow. About 10% to 20% of stomach cancers are HER2-positive, meaning they have too much of this protein. If your cancer is HER2-positive, you may be eligible for targeted therapies like trastuzumab, a drug that blocks HER2 and slows cancer growth.^[9][15] Testing for HER2 is done on the biopsy sample taken during endoscopy.

Another important biomarker is microsatellite instability (MSI) or mismatch repair deficiency (dMMR). These are signs that the cancer cells have problems fixing errors in their DNA. Cancers with high MSI or dMMR may respond well to immunotherapy, a type of treatment that helps your immune system fight cancer.^[8]

Programmed cell death ligand 1 (PD-L1) is another biomarker that can be tested. PD-L1 is a protein on the surface of some cancer cells that helps them hide from the immune system. Testing for PD-L1 can help determine whether immunotherapy drugs, such as pembrolizumab or nivolumab, might be beneficial.^[8][15]

Standard Tests for Clinical Trials

In addition to biomarker testing, clinical trials often require standard diagnostic procedures such as CT scans, PET scans, blood tests, and performance status assessments. Performance status is a measure of how well you are able to carry out daily activities and how the cancer is affecting you. Doctors use this information to decide if you are strong enough to tolerate the treatments being tested in the trial.^[5]

Some trials may also require additional tests, such as checking your heart function with an electrocardiogram (ECG) or an echocardiogram, or evaluating your kidney and liver function with blood tests. These tests help ensure that it is safe for you to receive the experimental treatment.^[5]

If you are considering joining a clinical trial, ask your doctor which tests are needed and what they involve. Clinical trials can offer access to new treatments that are not yet widely available, and they contribute to advancing knowledge about how to better treat stomach cancer for future patients.^[5]