Stomach cancer develops when cells in the lining of the stomach grow and divide in an abnormal way. Tumours can begin anywhere in the stomach, although most start in the glandular tissue found on the stomach’s inner surface (mucosa). This type of cancer is called adenocarcinoma of the stomach (also known as gastric cancer).
If it is not found and treated early, stomach cancer can spread through the lymphatic system to nearby lymph nodes or through the bloodstream to other parts of the body, such as the liver and lungs. It may also spread to the walls of the abdomen (peritoneum). Rarely, it can grow through the stomach wall into nearby organs such as the pancreas and bowel.
Once the second most common cancer worldwide, stomach cancer has dropped to sixth place, after cancers of the lung, breast, prostate, colon and rectum, and skin (non-melanoma). Stomach cancer is the third most common cause of death from cancer. The World Health Organization estimates that in 2018, gastric cancer accounted for 783,000 deaths worldwide.
Types of Stomach Cancer
Different types of stomach cancer include:
Adenocarcinomas of the stomach develop in the cells of the innermost lining of the stomach. Most stomach cancers are classified as adenocarcinomas of the stomach.
Lymphoma is a cancer of the immune system tissue that may start anywhere lymph tissues are found, including the stomach. Lymphomas in the stomach are rather rare and only account for about 4 percent of all stomach cancers.
Gastrointestinal stromal tumors, or GISTs, are a rare type of stomach cancer that forms in a special cell found in the lining of the stomach called interstitial cells of Cajal (ICCs). Under a microscope, GIST cells look similar to muscle or nerve cells. These tumors may develop throughout the digestive tract, but about 60 to 70 percent occur in the stomach.
Carcinoid tumors typically start in the hormone-producing cells of the stomach. These tumors usually do not spread to different organs and account for only about 3 percent of stomach cancer incidence.
Gastric carcinoid tumors come in three types:
- Type I and II ECL-cell carcinoids rarely spread to other parts of the body and may produce no symptoms. They are most often discovered during an endoscopy for another health issue, such as acid reflux.
- Type III ECL-cell carcinoids are more aggressive. The excess hormone secretion of carcinoid tumors may lead to a condition called carcinoid syndrome, marked by flushing, abdominal pain, diarrhea, constriction of the bronchial tubes in the lungs and, in some cases, heart troubles like valve dysfunction. Carcinoid syndrome is a sign that more aggressive treatment may be required.
Stomach cancer risk factors
Some risk factors can be attributed to lifestyle and therefore can be changed. However, there are also risk factors that cannot be controlled. Having a risk factor(s) does not mean you will get the disease, but scientists have found several risk factors that make a person more likely to get stomach cancer. They are:
- Gender–it is more common in men than women.
- More common in those of Hispanic, African, Native American and Pacific Islander descent than Caucasians.
- People with mucosa-associated lymphoid tissue (MALT) lymphoma have an increased risk.
- Diets with high amounts of smoked foods, salted meat and fish, and pickled vegetables.
- Smoking increases risk
- Being overweight or obese is a possible cause of gastric cancers.
Causes of Stomach Cancer
Scientists don’t know exactly what makes cancer cells start growing in the stomach. But they do know a few things that can raise your risk for the disease. One of them is infection with common bacteria, H. pylori, which causes ulcers. Inflammation in your gut called gastritis, a certain type of long-lasting anemia called pernicious anemia, and growths in your stomach called polyps also can make you more likely to get cancer.
Other things that seem to play a role in raising the risk include:
- Being overweight or obese
- A diet high in smoked, pickled, or salty foods
- Stomach surgery for an ulcer
- Type-A blood
- Epstein-Barr virus infection
- Certain genes
- Working in coal, metal, timber, or rubber industries
- Exposure to asbestos
Symptoms and Signs
People with stomach cancer may experience the following symptoms or signs. Sometimes, people with stomach cancer do not have any of these changes. Or, the cause may be a different medical condition that is not cancer.
Stomach cancer is usually not found at an early stage because it often does not cause specific symptoms. When symptoms do occur, they may be vague and can include those listed below. It is important to remember that these symptoms can also be caused by many other illnesses, such as a stomach virus or an ulcer.
- Indigestion or heartburn
- Pain or discomfort in the abdomen
- Nausea and vomiting, particularly vomiting up solid food shortly after eating
- Diarrhea or constipation
- Bloating of the stomach after meals
- Loss of appetite
- Sensation of food getting stuck in the throat while eating
Symptoms of advanced stomach cancer may include:
- Weakness and fatigue
- Vomiting blood or having blood in the stool
- Unexplained weight loss
Complications of Stomach Cancer
If stomach cancer progresses to advanced stages, then it may lead to many complications like:
- Gastrointestinal bleeding
- Gastric perforation
- Small Bowel Obstruction
Stages of stomach cancer
The stages of adenocarcinoma of the stomach or esophagus include:
Stage I: At this stage, the tumor is limited to the top layer of tissue that lines the inside of the esophagus or stomach. Cancer cells also may have spread to a limited number of nearby lymph nodes.
Stage II: The cancer at this stage has spread deeper, growing into a deeper muscle layer of the esophagus or stomach wall. Cancer may also have spread to more of the lymph nodes.
Stage III: At this stage, the cancer may have grown through all the layers of the esophagus or stomach and spread to nearby structures. Or it may be a smaller cancer that has spread more extensively to the lymph nodes.
Stage IV: This stage indicates that the cancer has spread to distant areas of the body.
Diagnosis and test
If a doctor suspects stomach cancer, a thorough patient history will first be done. This includes asking about your lifestyle, such as tobacco or alcohol use and whether you have a family history of stomach cancer. A physical exam may follow, along with some of the following tests:
Stool tests called fecal occult blood test – to find blood in the stool that might not be visible to the naked eye
Barium swallow or upper gastrointestinal (GI) series – the patient swallows a barium solution and the doctor uses an X-ray to track the barium’s progress as it passes through the esophagus and stomach
Endoscopy – A small tube with a light on one end is slid down the throat and into the stomach so the doctor can look directly at the stomach lining
Biopsy – Using a gastroscopy instrument that’s fitted with a special cutter, a small piece of tissue can be taken and examined under a microscope
If cancer is diagnosed, the doctor needs to determine the stage the cancer has reached. This may involve more tests, such as:
- Chest X-rays
- Computed tomography (CT) scans
- Magnetic resonance imaging (MRI) scans
- PET scan
- Diagnostic laparoscopy
- Blood tests
In its early stages, stomach cancer is very treatable. Unfortunately, early stomach cancer causes few symptoms. Usually, a diagnosis is made when the cancer is more advanced. Because it can take some time to identify stomach cancer, only about 10% of people are diagnosed while it’s still in the early stages.
Stomach Cancer Treatment
Common treatments include:
Surgery is often the primary treatment for this type of cancer.
Chemotherapy may be used in combination with surgery and radiation therapy.
Radiation approaches may be used to treat adenocarcinoma of the stomach or lymphoma of the stomach. It may help destroy cancer cells that remain after stomach cancer surgery, alleviate pain and stop bleeding or shrink tumors that may be blocking the digestive tract. Radiation therapies used to treat stomach cancer include:
Intensity modulated radiation therapy (IMRT) allows a radiation oncologist to use higher radiation doses than traditional therapies. IMRT may also help spare more of the surrounding healthy stomach tissue from harmful doses of radiation.
Trilogy® allows a radiation oncologist to deliver controlled doses of radiation to stomach tumors with increased accuracy. The technology’s real-time imaging allows a radiation therapist to monitor stomach tumor motion during treatment.
TomoTherapy® combines IMRT and CT scan technology and is designed to deliver precise radiation to match tumor shapes while avoiding sensitive healthy tissue. TomoTherapy targets hard-to-reach stomach tumors by sculpting small, powerful and more precise radiation beams at the tumors from a full 360 degrees.
Interventional radiology may be a treatment option for stomach cancer that has spread to the liver. These minimally invasive procedures allow doctors to deliver radiation or chemotherapy drugs in high doses directly into liver tumors.
Immunotherapy drugs called checkpoint inhibitors work by blocking signaling receptors that help cancer cells hide from immune cells. The U.S. Food and Drug Administration have approved a checkpoint inhibitor to treat some forms of advanced or metastatic adenocarcinomas in the stomach and the gastroesophageal junction, where the stomach meets the esophagus. Checkpoint inhibitors and other immunotherapy treatments may be used in combination with other treatments, such as surgery. Immunotherapy may not be recommended for all patients, and responses to the treatment vary widely.
Targeted therapy may be a treatment option for patients with advanced stomach cancer whose cancer cells test positive for human epidermal growth-factor receptor 2 (HER2). This means their stomach tumors have a type of gene that stimulates cells to grow and become cancerous. HER2-positive stomach cancers may be treated with a monoclonal antibody that targets the HER2 gene. This drug, often used to treat HER2-postive breast cancer, may be used in combination with chemotherapy for stomach cancer. In some cases, this form of targeted therapy may be used alone.
Gastroenterology procedures may be required to diagnose, stage or treat stomach cancer. These procedures include placing stents or inserting tubes and balloon dilation to relieve obstructions.
Screening programs are successful in detecting disease in the early stages in parts of the world where the risk of stomach cancer is much higher than in the United States. The value of screening in the United States and other countries with much lower rates of stomach cancer is not clear.
The following may help reduce your risk of stomach cancer:
- Do not smoke.
- Keep a healthy diet rich in fruits and vegetables.
- Take medicines to treat reflux disease (heartburn), if you have it.
- Take antibiotics if you are diagnosed with H. pylori infection.