The stomach is an organ made up of 5 sections that plays a role in digestion. Food enters the stomach from the esophagus via the gastroesophageal junction, mixes with gastric juice to begin the process of digestion, and is eventually emptied into the duodenum (the first part of the small intestine). Cancers beginning in different portions of the stomach will have different symptoms, different treatment plans, and different prognoses.[1]
About 1.3% of new cancers diagnosed in the United States are stomach cancers[2]. It is more common in men than women, and usually affects older individuals. The average age at diagnosis is 68, with about 60% of new diagnoses occurring after the age of 65. Stomach cancer has become less common in the US in the latter half of the 20th century, but it remains one of the leading causes of cancer-related deaths worldwide.
Early stomach cancers rarely cause symptoms, but as the disease progresses, it may cause[3]:
Unexplained weight loss and loss of appetite
Abdominal pain
Discomfort in the region just above the navel
Trouble swallowing
Weight loss and loss of appetite
Nausea
Heartburn
Vomiting (with or without blood)
Fatigue
A feeling of fullness after eating very little
Swelling or fluid build-up in the abdomen
Stool that appears dark brown or black (a sign of blood in the stool)
Anemia
Jaundice (usually a sign the cancer has spread to the liver)
These symptoms may be caused by any number of health conditions, and should be evaluated by a medical professional.
Stomach cancer can present with various subtypes, each characterized by distinct features and biological behaviors:
Adenocarcinoma: Between 90% and 95% of stomach cancers are adenocarcinomas. The intestinal type is much more common, and tends to respond better to treatment. Diffuse adenocarcinoma is rarer, spreads faster, and is harder to treat.
Neuroendocrine tumor: Neuroendocrine cells act like neurons in some ways, and endocrine cells in others. Cancers that begin in these cells–found throughout the digestive system–tend to grow less rapidly than other forms of stomach cancer, and are less likely to spread to other organs.
Lymphoma: Cancers of the immune system usually form in other parts of the body first, but can originate in the wall of the stomach.
Gastrointestinal stromal tumor (GIST): GIST tumors form in a specialized nerve cell found in the wall of the stomach. These tumors are uncommon, and some are much more likely to spread quickly to other parts of the body.
Survival rates and incidence
Stomach cancer survival rates are based on how far it has spread:
Localized: There is no sign the cancer has spread outside the stomach.
Regional: The cancer has spread to nearby structures or lymph nodes
Distant: The cancer has spread to distant parts of the body.
The 5-year survival rate for each stage is shown below:
Below is the overall incidence of stomach cancer by age group:
Risk Factors
There are several confirmed risk factors that contribute to an individual’s risk for stomach cancer:
Biological sex: Men are more likely to develop stomach cancer than women; for people assigned male at birth, the overall lifetime risk of developing stomach cancer is about 1 in 101, whereas for people assigned female at birth, that risk decreases significantly, to 1 in 155.
Smoking & secondhand smoke exposure: Smoking and secondhand smoke increases your risk of many cancers, including stomach. Tobacco smoke contains numerous carcinogens that can lead to genetic mutations and uncontrolled cell growth, ultimately resulting in cancer. Quitting smoking at any age can significantly reduce the risk of cancer and other smoking-related diseases. The body begins to repair itself almost immediately after quitting, with the risk of cancer decreasing over time. Even individuals who have smoked for many years can benefit from quitting, as the risk decreases with each year of abstinence.
Occupation: Coal and tin miners, metal processors, and rubber industry workers are all at an increased risk of stomach cancer, though the mechanisms for this are not well understood.
Alcohol use: Alcohol has been shown to increase the risk of stomach cancer, particularly in individuals who consume three or more drinks daily.
Previous stomach surgery: Individuals who have had a portion of the stomach removed to treat non-cancerous conditions such as ulcer have a higher rate of stomach cancer overall. This may be because the stomach produces less acid after surgery, allowing certain harmful bacteria to proliferate, or it may be due to reflux of bile from the small intestine post-surgery.
Health conditions: some text
Gastroesophageal reflux disease (GERD): This chronic form of acid reflux is known to increase the risk of stomach and esophageal cancers.
Helicobacter pylori (H pylori) infection: This bacteria is thought to contribute to a large proportion of stomach cancers, particularly those in the lower portion of the stomach. Though many individuals carry this germ and never go on to develop stomach cancer, long-term H pylori infection may lead to pre-cancerous changes to the stomach lining.
Epstein-Barr virus infection: While it’s unclear if this virus–which causes mononucleosis–causes stomach cancer, it has been linked to other cancers, and has been found in cancer cells in about 5-10% of stomach cancers. Stomach cancers linked to Epstein-Barr virus tend to grow more slowly and are less likely to spread.
Hiatal hernia: A hiatal hernia is a bulging of the upper portion of the stomach through the diaphragm and into the chest cavity. This condition is linked to chronic reflux.
Pernicious anemia: Pernicious anemia affects the body’s ability to absorb vitamin B12, and can arise from a variety of autoimmune diseases as well as from surgeries such as gastric bypass. Regardless of cause, the syndrome increases one’s risk for stomach cancer.
Menetrier disease: This condition causes large folds in the lining of the stomach and low levels of stomach acid. It’s known to increase stomach cancer risk, but the rarity of the disorder means its contribution is not well understood.
Common variable immune deficiency (CVID): Individuals with CVID are unable to produce enough antibodies to fight germs in the body. This can lead to frequent infections and conditions such as pernicious anemia, and is known to increase the risk of stomach cancer.
Genetic conditions: Certain genetic conditions increase the risk of stomach cancers. These include: some text
Lynch syndrome
Juvenile polyposis syndrome
Hereditary diffuse gastric cancer (HDGC)
Peutz-Jeghers syndrome
Familial adenomatous polyposis
Gastric adenoma and proximal polyposis of the stomach (GAPPS)
Li-Fraumeni syndrome
Family history: People with a first-degree relative (parent, sibling, or child) who have had stomach cancer have an increased risk, even in the absence of an inherited genetic syndrome.
Blood type A: Individuals with type A blood are at higher risk for stomach cancer, though the reasons for this are unknown.
Protective Factors
Several factors have been shown to have protective effects against stomach cancer:
Maintaining a healthy weight: Numerous studies have linked higher BMI to increased risk of various types of cancer, including stomach cancer. Excess body fat can lead to higher levels of estrogen and insulin, as well as increased production of insulin-like growth factors. Higher BMI is also associated with chronic low-level inflammation, which can cause DNA damage over time and contribute to the development of cancer. Maintaining a healthy weight helps you to avoid these risks.
Physical activity: Regular exercise can reduce your risk of several types of cancer through a combination of physiological, hormonal, and immunological changes. It can reduce inflammation, improve immune function, improve hormonal regulation, and lower insulin levels. The American Cancer Society recommends engaging in at least 150 minutes of moderate activity or 75 minutes of vigorous activity each week. Furthermore, data indicates that individuals can see significant incremental benefit with additional exercise.
Fruit and vegetable consumption: Fruit and vegetables are rich in various nutrients which have been shown to have protective effects against multiple cancers, including stomach. These foods contain a variety of antioxidants, which help neutralize free radicals in the body and reduce inflammation. Citrus fruits in particular seem to reduce the risk of stomach cancer.
Lower salt / processed meat consumption: Diets high in salt and processed meats have been tied to higher rates of stomach cancer[4][5], though more studies are needed to definitively confirm causation. In general, diets lower in salt, processed meat, and red meat are correlated to lower risk for multiple types of cancer.
Oily fish consumption: Oily fish (such as salmon, mackerel, trout, sardines, and herring) are known to have various health benefits. Rich in omega-3 fatty acids, protein, vitamins, and minerals, studies have shown that eating oily fish has protective effects against several types of cancer, including stomach, and that increased consumption increases these benefits.
NSAIDS: Nonsteroidal anti-inflammatory drugs (NSAIDs) are a class of medications commonly used to relieve pain, reduce inflammation, and lower fever, and they have also been shown to reduce stomach cancer risk with regular use. In addition to their anti-inflammatory properties, NSAIDs have been shown to inhibit cell proliferation, induce programmed cell death, suppress tumor growth, and modulate immune responses. While NSAIDs have been associated with potential benefits in cancer prevention, their use is not without risks. Long-term or high-dose NSAID use has been linked to gastrointestinal bleeding, ulcers, and perforation. Additionally, certain NSAIDs have been associated with an increased risk of cardiovascular events such as heart attack and stroke.
Statins: Statins are a class of prescription drugs that lower cholesterol levels and can reduce the risk of heart attack and stroke, and studies have shown that statins may also lower the risk of several cancers, including stomach. While the exact mechanism is unknown, this could be due to several factors. Statins have anti-inflammatory properties that may inhibit the inflammatory processes involved in cancer development and progression.
Green tea: Some studies have shown that consumption of green tea reduces the risk of stomach cancer[6]. The reduction seems to correlate with the amount of tea consumed.
Blood type O: While people with blood type A are at increased risk for stomach cancer, those with blood type O have a reduced risk of the disease.
Screening
Early detection of stomach cancer has a dramatic impact on prognosis. The 5-year survival rate for localized cancer is over 75%, but drops to just 7% once the cancer has spread to distant parts of the body.
Depending on your age and risk factors, the optimal stomach cancer screening will vary:
Medical history / physical exam: A thorough medical history and physical examination is often the best first test for possible stomach cancer. Knowing your family history, any recent changes you’re experiencing, and carefully palpating your abdomen can all help a doctor diagnose stomach problems, including stomach cancer. If your doctor does find anything concerning, they will likely refer you to a gastroenterologist.
Upper endoscopy: During this test, a doctor passes a thin, flexible camera down the esophagus and into the stomach and upper intestine, allowing them to examine the inner lining of these organs. If anything abnormal is seen, a tissue sample can be taken for biopsy via the endoscope. In some instances, early stage cancers can be removed via endoscopy.
Blood and fecal tests: Blood tests for issues such as anemia (which may indicate cancer) and fecal tests that can detect blood in the stool not visible to the naked eye can both indicate the presence of stomach cancer, though further testing would be required to confirm this diagnosis.
Imaging tests: CT scans, x-rays, positron emission tomography (PET) scans, and ultrasounds (generally in the form of an endoscopic ultrasound) can all be used to look for stomach cancer, or to determine the extent to which the cancer has spread. Less commonly, MRIs are used for this purpose.
Liquid biopsy: Liquid biopsy is an investigational cancer-detection technique which looks for DNA fragments in the blood to determine whether cancer is present. Though still in its infancy, this technology is promising, particularly in screening for hard-to-detect cancers or cancers whose symptoms are minimal or tend to appear only after they’ve spread. Stomach cancer is one of many cancers which can be screened for via this method.
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