Gastric cancer – Diagnostics – Overview of Information and Clinical Research

Diagnosing gastric cancer requires careful examination and specialized tests to identify the disease and determine the best treatment approach. Since symptoms often appear late, understanding when to seek medical attention and what diagnostic procedures involve can help patients make informed decisions about their health care.

Who Should Undergo Diagnostics and When to Seek Medical Attention

Anyone experiencing persistent digestive symptoms should consider consulting a healthcare provider, as gastric cancer often develops silently without obvious early warning signs. Many of the common symptoms—such as stomach discomfort, heartburn, or indigestion—can easily be mistaken for less serious conditions, which is why it’s important to pay attention when these problems don’t go away or worsen over time.^[1]

You should seek medical evaluation if you notice unexplained weight loss, especially when it occurs without trying to lose weight. This is one of the more telling signs that something may be wrong with your digestive system. Similarly, trouble swallowing, persistent nausea and vomiting, or a constant feeling of fullness after eating only small amounts are symptoms that deserve prompt attention.^[3]

Certain groups of people face higher risks and may benefit from more vigilant monitoring. If you are 65 years or older, your risk increases significantly, as the average age of diagnosis is around 68.^[1]^[3] Men are almost twice as likely as women to develop gastric cancer. Your ethnic background also plays a role—people of South or Central American, Eastern European, or East Asian descent have higher rates of this disease.^[5]

Family history matters too. If you have close relatives who have had gastric cancer, or if you have been diagnosed with certain genetic conditions like hereditary diffuse gastric cancer syndrome, Lynch syndrome, or familial adenomatous polyposis, your doctor may recommend earlier or more frequent screening.^[3]^[5]

⚠️ Important

If you notice black or tarry stools, or if you vomit blood, seek immediate medical attention. These can be signs of bleeding in your digestive system and require urgent evaluation. Similarly, jaundice—when your skin and eyes turn yellow—or severe stomach pain that doesn’t improve should prompt an emergency visit to your doctor.^[3]

People with certain medical conditions should also be more alert. If you have chronic Helicobacter pylori infection (a type of bacteria that lives in the stomach), gastroesophageal reflux disease (GERD) (when stomach acid frequently flows back into the tube connecting your mouth and stomach), or a history of stomach ulcers or polyps, these conditions can increase your risk of developing gastric cancer over time.^[5]^[11]

Lifestyle factors also influence who should be more vigilant. If you smoke, drink alcohol heavily, or follow a diet high in salty, smoked, or pickled foods while eating few fruits and vegetables, your risk rises. Obesity is another factor that can contribute to the development of this disease.^[5]

In countries where gastric cancer is more common, public screening programs help detect the disease early, when survival rates are much better. However, in the United States and other Western countries, routine screening for stomach cancer is not standard unless you have specific risk factors or symptoms.^[2]

Classic Diagnostic Methods Used to Identify Gastric Cancer

When you visit your doctor with symptoms that suggest a possible problem in your stomach, the first step usually involves a detailed conversation about your medical history and a physical examination. During the physical exam, your doctor may feel your abdomen to check for masses, swelling, or tenderness. Sometimes, if the cancer is advanced, a mass might be felt through the abdominal wall, though this is not always the case.^[3]

Endoscopy, also called gastroscopy or upper endoscopy, is the most important diagnostic tool for stomach cancer. This procedure allows doctors to look directly inside your esophagus, stomach, and the upper part of your small intestine using a thin, flexible tube with a light and camera at the end. The tube is gently passed through your mouth and down your throat while you are sedated to keep you comfortable.^[5]^[8]

During the endoscopy, if the doctor sees anything abnormal—such as areas that look inflamed, ulcerated, or suspicious for cancer—they can take small tissue samples called biopsies. These tissue samples are then sent to a laboratory where a specialist examines them under a microscope to determine whether cancer cells are present. This tissue examination is essential because it confirms the diagnosis and provides information about the type of cancer.^[8]

Endoscopy is particularly valuable because it can detect early-stage tumors, which may be small and have not yet caused noticeable symptoms. In some cases, early tumors can even be removed during the endoscopy procedure itself, which is called endoscopic mucosal resection. This approach works well when the cancer is still confined to the innermost lining of the stomach and has not spread deeper into the stomach wall or to other parts of the body.^[9]

Blood tests are commonly performed as part of the diagnostic process. While no single blood test can diagnose gastric cancer on its own, these tests help doctors assess your overall health, check for anemia (which can result from bleeding in the stomach), and evaluate how well your liver and kidneys are functioning. Blood tests can also look for signs of H. pylori infection, which is a known risk factor for developing gastric cancer.^[8]

Once cancer is confirmed through biopsy, additional imaging tests are usually needed to determine how far the disease has spread. This process, called staging, helps your medical team understand whether the cancer is limited to the stomach or has reached nearby lymph nodes or distant organs.^[8]

Computed tomography (CT) scans use X-rays and computer technology to create detailed cross-sectional images of your abdomen and chest. These scans can show the size and location of the tumor, whether it has grown through the stomach wall, and if it has spread to nearby lymph nodes, liver, lungs, or other organs. CT scans are a standard part of staging for gastric cancer.^[8]

Positron emission tomography (PET) scans may be used in some cases to help detect cancer cells throughout the body. During a PET scan, a small amount of radioactive sugar is injected into your bloodstream. Cancer cells, which use more sugar than normal cells, absorb this substance and appear as bright spots on the scan. PET scans can be helpful in finding cancer that has spread beyond the stomach.^[8]

Endoscopic ultrasound is a specialized procedure that combines endoscopy with ultrasound imaging. A small ultrasound device is attached to the end of the endoscope, allowing the doctor to see detailed images of the stomach wall layers and nearby lymph nodes. This test is particularly useful for determining how deeply the cancer has invaded the stomach wall and whether nearby lymph nodes are involved.^[8]

In some situations, your doctor may order a laparoscopy, a surgical procedure done under general anesthesia. During laparoscopy, a surgeon makes small incisions in your abdomen and inserts a thin tube with a camera to look directly at the stomach and surrounding organs. This allows the surgeon to check for cancer spread that might not be visible on imaging scans. Small tissue samples can also be taken during this procedure.^[8]

If your doctor suspects that cancer may have spread to your chest or if you are having trouble swallowing, a chest X-ray or barium swallow test might be recommended. During a barium swallow, you drink a liquid containing barium, which coats the lining of your esophagus and stomach. This coating shows up clearly on X-rays and can reveal abnormalities in these areas.^[8]

Diagnostics for Clinical Trial Qualification

Clinical trials are research studies that test new treatments or combinations of treatments to find better ways to help patients with gastric cancer. To participate in a clinical trial, you must meet specific criteria, and diagnostic tests play a key role in determining whether you qualify.^[10]

Before enrolling in a trial, you will undergo a thorough evaluation that includes many of the same tests used for standard diagnosis and staging. Endoscopy with biopsy is essential to confirm that you have gastric adenocarcinoma and to identify the specific type of cancer cells. The biopsy samples are often sent for additional laboratory tests to look for specific genetic changes or molecular markers in the cancer cells.^[10]

One important marker that researchers often test for is HER2 (human epidermal growth factor receptor 2). HER2 is a protein found on the surface of some cancer cells. When cancer cells have too much HER2, the cancer is called HER2-positive. Certain targeted therapies work specifically against HER2-positive cancers, so knowing your HER2 status can help determine which clinical trials you might be eligible for.^[10]

Another key test is for microsatellite instability (MSI) or mismatch repair deficiency (dMMR). These terms describe problems in the way cancer cells repair mistakes in their DNA. Cancers with high microsatellite instability or mismatch repair deficiency often respond well to a type of treatment called immunotherapy, which helps your immune system fight cancer. Clinical trials testing immunotherapy treatments often require patients to have MSI-high or dMMR tumors.^[10]

PD-L1 (programmed death-ligand 1) testing is another molecular test that may be performed. PD-L1 is a protein that some cancer cells use to hide from the immune system. Tumors with high levels of PD-L1 may respond better to certain immunotherapy drugs. Knowing your PD-L1 status can help researchers determine if a particular trial focused on immunotherapy is right for you.^[10]

⚠️ Important

Molecular testing and biomarker analysis are becoming increasingly important in personalizing cancer treatment. These tests look at the genetic makeup of your tumor and can identify specific abnormalities that might be targeted by newer drugs. Talk to your doctor about whether molecular testing is appropriate for you, as it can open doors to clinical trials and treatment options that might not otherwise be available.^[10]

Imaging studies like CT scans and PET scans are also required for clinical trial enrollment. These scans provide a baseline measurement of the tumor size and location, which researchers use to track how well the treatment is working during the trial. You may need to have these scans repeated at regular intervals throughout the study.^[10]

Your overall health and physical condition are carefully assessed before you can join a clinical trial. Doctors use a system called performance status to rate how well you are able to carry out daily activities. This rating helps researchers determine if you are strong enough to tolerate the experimental treatment being studied. Blood tests that check your liver function, kidney function, and blood cell counts are also standard requirements for most trials.^[10]

Some clinical trials focus on specific stages of gastric cancer. For example, trials testing treatments for early-stage disease may only accept patients whose cancer has not spread beyond the stomach, while trials for advanced or metastatic disease may require evidence that the cancer has spread to distant organs. Your staging tests—including imaging and sometimes surgical evaluation—determine which trials you are eligible for.^[10]

In addition to these tests, clinical trial teams may require you to undergo testing for Epstein-Barr virus (EBV) infection in the tumor. Some gastric cancers are associated with EBV, and this subset of tumors may respond differently to certain treatments. Identifying EBV-associated cancers can help match patients to trials investigating therapies specifically designed for these tumors.^[5]

It’s important to understand that qualifying for a clinical trial involves meeting many specific criteria, and not everyone will be eligible for every trial. Your medical team can help you explore which trials might be appropriate for your situation and guide you through the testing process required for enrollment.^[10]

Prognosis and Survival Rate

Prognosis

The prognosis for gastric cancer patients depends on several important factors, with the stage at diagnosis being the most significant. When cancer is detected early and is still confined to the stomach lining without spreading to lymph nodes or other organs, the chances of successful treatment and long-term survival are much better. More than 50 percent of patients with localized distal gastric cancer (cancer in the lower part of the stomach that has not spread) can be cured.^[11]^[14]

Unfortunately, early-stage disease accounts for only 10 to 20 percent of all gastric cancer cases diagnosed in the United States. Most patients are diagnosed when the cancer has already spread to regional lymph nodes or distant sites in the body. When cancer has spread beyond the stomach, the prognosis becomes more challenging.^[14]

The extent of tumor spread plays a critical role in determining outcomes. This includes whether the cancer has grown through the stomach wall and whether it has reached nearby lymph nodes. Tumors that have invaded deeper layers of the stomach wall or spread to multiple lymph nodes generally have a less favorable prognosis. The tumor grade—which describes how abnormal the cancer cells look under a microscope—also provides some prognostic information, with poorly differentiated tumors typically behaving more aggressively.^[11]^[14]

Other factors that can influence prognosis include your overall health and physical condition, your age, and how well you respond to treatment. Patients who are healthy enough to undergo surgery followed by chemotherapy often have better outcomes than those who cannot tolerate these treatments. The specific molecular characteristics of the tumor, such as HER2 status or microsatellite instability, can also affect prognosis and treatment options.^[10]

Survival Rate

Survival rates for gastric cancer vary widely depending on the stage at diagnosis. For localized disease that has not spread beyond the stomach, the five-year overall survival rate can be as high as nearly 50 percent for patients with resectable regional disease. This means that about half of patients whose cancer is confined to the stomach and nearby areas, and who undergo appropriate treatment, are still alive five years after diagnosis.^[14]

However, when gastric cancer is diagnosed at an advanced stage with metastatic disease—meaning it has spread to distant organs such as the liver or lungs—the five-year survival rate drops dramatically to just 5 percent. For patients with metastatic disease, the median overall survival with conventional chemotherapy is approximately 12 months.^[2]^[10]

It’s important to remember that survival statistics are based on large groups of patients and represent averages. Individual outcomes can vary significantly based on many factors, including the specific characteristics of your cancer, how it responds to treatment, and advances in medical care. Newer treatments, including targeted therapies and immunotherapies, have shown promising results in improving survival for certain subgroups of patients, particularly those with specific molecular markers like HER2-positive or MSI-high tumors.^[10]

The incidence of gastric cancer has been declining steadily in the United States over the past several decades, with new cases dropping by about 1.5 percent each year over the last 10 years. This decline is partly attributed to improved understanding of risk factors, better diagnostic techniques, and more effective treatments. However, there has been a concerning increase in gastric cancer cases among younger adults under 50 years of age, with rates rising by about 3 percent between 2004 and 2015.^[1]^[10]