Gastrointestinal (GI) Cancer Facts

November 22, 2024

This page was reviewed under our medical and editorial policy by Laleh Melstrom, M.D., M.S., associate professor of surgery and immuno-oncology, Division of Surgical Oncology, Department of Surgery, City of Hope^® Cancer Center Duarte

Gastrointestinal (GI) cancer includes any type of cancer that begins growing in the digestive system. The most common types in the United States include colorectal, pancreatic and liver cancers. GI cancers include a wide range of diseases, and they may start in other areas from the esophagus to the anus, or other organs such as the gallbladder.

As a group, GI cancers contribute to more than one-quarter of new cancers and more than one-third of cancer-related deaths worldwide.

This guide provides an overview of GI cancers, explaining what makes each type its own distinct disease and how each is typically detected.

What Is Gastrointestinal Cancer?

Gastrointestinal cancers often start when tumors form along the GI tract, which runs from the esophagus (the tube food goes down), through the stomach and to the intestines and the anus. GI cancer may also develop in digestive organs, such as the liver, pancreas or gallbladder.

Cancer forms when the instructions for normal growth in cells are abnormal — this makes the cells grow uncontrollably or not die off as they normally do, forming a tumor.

Sometimes, cancer spreads to the digestive system from another location. For example, breast cancer may metastasize (spread) to the liver. However, these cancers are not called GI cancers because they began outside the digestive system.

The following cancers are types of GI cancer. It is important to remember that each is a distinct disease, which may require a specialized treatment approach.

Esophageal cancer: Cancerous cells may form lesions or tumors in the wall of the esophagus, the passageway from the throat to the stomach. Esophageal cancers are classified according to the type of cell from which they grow. Those that begin in mucus-producing cells are called adenocarcinomas; those that begin in the esophagus’ inner layer (mucosa) are called squamous cell carcinomas. There is no generally recommended screening for esophageal cancer, and most cases are found after a person has signs or symptoms. Sometimes, it is found during tests for other health conditions. Anyone who has symptoms of ongoing hoarseness, trouble swallowing or weight loss should be evaluated.

Stomach cancer: Also called gastric cancer, stomach cancers usually develop over many years. Some occur in the upper stomach near the esophagus (cardia). Those in other areas are called non-cardia stomach cancers. Because symptoms may go unnoticed in the early stages and screening is not routine, stomach cancer is often diagnosed only after it has spread. Almost all stomach cancers are an adenocarcinoma type, meaning they have begun in mucus-producing cells. Other types include neuroendocrine, GI stromal tumors and lymphomas. Patients with a high risk for developing stomach cancer, including those with some genetic conditions, such as Lynch syndrome or familial adenomatous polyposis, or a family history of stomach cancer, may benefit from regular screening.

Colorectal cancer: Cancerous tumors that form within the colon or rectum are called colorectal cancer. Most begin as precancerous growths called polyps in the lining of the intestine, and most cases are classified as adenocarcinomas. These cancers start in the mucous-producing cells of the lining of the colon and rectum. Routine colorectal cancer screening with a stool-based test or a visual examination of the colon (colonoscopy) is recommended beginning at age 45 (or sooner based on personal and family risk factors). A colonoscopy provides an opportunity to remove polyps before they become cancerous. Screening also helps catch colorectal cancer early when it is more treatable. Patients should inform their doctor if they have rectal bleeding, red- or black-colored stools or unexplained changes in bowel habits.

Anal cancer: This cancer may develop at the anal opening (anus) or within squamous cells in the inner lining of the anal canal. Symptoms may develop early on, allowing many anal lesions to be detected before they become cancerous. Most symptoms — rectal bleeding, unusual lumps or anal discomfort — are not due to cancer, but patients should have them checked out by their doctor to be safe. Screening is sometimes recommended for individuals with a higher risk for this cancer — including anyone who is HIV-positive, immunocompromised or has a history of anal warts; men who have sex with men; women who have had cancers of the cervix, vagina or vulva; and women over 45 who test positive for the human papillomavirus (HPV).

Pancreatic cancer: Cancer of the pancreas usually begins in exocrine cells (the cells that form the inner glands that make and release enzymes for digestion). Sometimes, precancerous lesions are detected by chance during an imaging test for another health condition. However, usually, pancreatic cancer is not detected until it reaches advanced stages. Patients with a family history of pancreatic cancer may undergo genetic testing. If high-risk markers are found, tests for early pancreatic cancer detection may be recommended.

Liver cancer: Though the liver is a common site for the spread of cancer from other parts of the body, these are not liver cancers. Liver cancer develops when cancer starts in the liver itself, also known as primary liver cancer. Hepatocellular carcinoma is the most common type of liver cancer. Other more rare types are also possible. Since screening is not routinely done and early symptoms are uncommon, liver cancer is often diagnosed in advanced stages. Periodic testing may be recommended for patients at higher risk.

Bile duct cancer: Cholangiocarcinoma is another name for this cancer that forms in the bile ducts (tubes that carry a digestive fluid called bile from the liver to the small intestine). As the name implies, it is a type of adenocarcinoma. When cancer forms within bile ducts in the liver, it is called intrahepatic cholangiocarcinoma. Extrahepatic types form in parts of the bile duct outside the liver. The perihilar type forms in bile ducts just outside the liver, while distal bile duct cancers are located closer to the small intestine. Possible bile duct cancer symptoms may include nausea and vomiting, yellowing of skin and eyes, and unexplained weight loss.

Pancreatic neuroendocrine tumor (NET): This rare type of pancreatic cancer forms in endocrine cells that are found in clusters inside the pancreas. Tumors are grouped into those that make hormones (functioning) and those that do not (non-functioning). About half of NET tumors release hormones, most commonly insulin, into the blood. This may cause symptoms and lead to earlier detection. Symptoms vary depending on the type of hormones secreted, and may include pain, fatigue, diarrhea, unexplained weight loss and black, tarry stools. Non-functioning NETs are usually diagnosed later when symptoms such as stomach pain, yellowing of the eyes and weight loss develop.

Gallbladder cancer: This rare type of cancer is most often an adenocarcinoma, starting in gland cells that line the inside of the gallbladder. Early symptoms of gallbladder cancer may include belly pain, vomiting and loss of appetite, but these symptoms tend to be similar to ones patients might experience for other noncancerous conditions, and they are rarely due to gallbladder cancer. Diagnosis usually occurs in advanced stages.

GI stromal tumors (GISTs): This group of tumors forms along the GI tract, growing from interstitial cells of Cajal (ICCs), which help food and liquids move through the digestive system by signaling muscles to contract. Most GISTs form in the stomach, followed by the small intestine. But regardless of location within the GI tract, they are diagnosed as GI stromal tumors if the cancer grew from ICCs. Bleeding in the GI tract may lead to coughing up blood, red- or black-colored stools, and anemia.

Appendix cancer: Also referred to as appendiceal cancer, this rare cancer type forms in cells within the appendix. Early appendiceal cancer symptoms may include pain, bloating, nausea, vomiting or a feeling of fullness. These symptoms may not occur until the cancer is at a later stage.

How Common Is GI Cancer?

Among cancer types, gastrointestinal cancers are common, but some types are less common or even rare.

Colorectal cancer is by far the most common type of GI cancer in the United States. In fact, it is the third most common type of cancer diagnosed in both men and women. Among men under age 50, colorectal cancer is the most common type of cancer found.

The chances of being diagnosed with some of the more common types of GI cancer over the course of a lifetime are the following.

Colorectal cancer: 1 in 25 (women), 1 in 23 (men)

Pancreatic cancer: 1 in 60 (women), 1 in 58 (men)

Liver cancer (including ICC): 1 in 143 (women), 1 in 65 (men)

Stomach cancer: 1 in 155 (women), 1 in 101 (men)

Esophageal cancer: 1 in 434 (women), 1 in 127 (men)

These statistics are based on population averages in the United States. Some patients, however, may have individual risk factors that raise their personal risk for certain types of cancer.

What Causes GI Cancer?

Like other types of cancer, GI cancer is caused by genetic changes (mutations) in a cell’s blueprint (otherwise known as genes, which are pieces of DNA). These mutations cause the cells to grow and function abnormally. Most genetic changes that cause cancer are acquired, meaning they are not inherited from a person’s biological parents. Instead, these mutations happen during the course of a lifetime, sometimes randomly and sometimes due to factors like chemical or radiation exposure. And usually, multiple mutations occur before a cell turns cancerous.

Changes that “turn on” or “turn off” the genes that tell cells when to divide or die off may lead to cancer. 

A unique feature of cancer cells is their potential to metastasize, or spread into other tissues. For some cancers, this may happen slowly. Others may spread more rapidly, causing nearby organs or tissues to become cancerous (malignant). Through the circulatory or lymphatic systems, cancer may also spread to distant sites in the body.

When a person develops cancer, it is usually not due to one specific known cause. A combination of lifestyle, environmental and genetic factors often contribute. A patient’s health conditions or exposures to pathogens may also play a role.

While the specific cause(s) of GI cancer may be unknown, several known factors may increase an individual’s risk for developing GI cancer.

Gastrointestinal Cancer Risk Factors

Some GI cancer risk factors are things patients cannot change (non-modifiable) — age being the most common. Because genetic mutations accumulate over a lifetime, the risk of cancer increases with age. Older patients may also have more chronic health conditions that raise the risk of GI cancer.

Genetics are another non-modifiable risk factor for GI cancer. In most cases, one specific gene is not the issue. More likely, combinations of genes or genetic conditions like Lynch syndrome are associated with an increased risk for GI cancer. Patients may also have genetic profiles that indirectly contribute to their GI cancer risk by increasing their odds of having another condition, like obesity or diabetes, that ups the risk for GI cancer.

Non-modifiable risk factors for GI cancers may include:

• Older age
• Male sex at birth
• Certain racial or ethnic backgrounds (colorectal cancer rates are higher for American Indian and Alaskan Native people, African Americans and Askkenazi Jews of Eastern European descent; Hispanic Americans have higher rates of stomach and liver cancers)
• Personal or family history of GI cancer or colon polyps
• Certain medical conditions, such as Barrett’s esophagus or inflammatory bowel disease
• Lynch syndrome or other hereditary conditions linked to cancer formation
• Exposure to radiation of the pelvis or abdomen
• Past infections caused by hepatitis B virus, hepatitis C virus, human papillomavirus (HPV) or Helicobacter pylori

While exposure to past infections cannot be changed, some cancer-related infections may be prevented through vaccinations. The U.S. Centers for Disease Control and Prevention recommends HPV and hepatitis B vaccination to prevent cancer.

Overall, more than 4 in 10 diagnosed cancers are estimated to be linked to modifiable risk factors that may be influenced or changed. And for colorectal cancer in particular, lifestyle habits are thought to be the cause of more than half of newly diagnosed cancers.

Common modifiable risk factors associated with GI cancers may include:

• Alcohol consumption (at any level)
• Excess body fat
• Sedentary lifestyle
• History of smoking
• Regular consumption of red, processed or grilled meats
• A low-fiber or high-fat diet
• A diet low in fruits, vegetables and calcium

Keep in mind that having risk factors for cancer does not mean cancer will develop. Likewise, patients with no risk factors for cancer may still develop cancer. Patients should talk with doctors about their individual risk for GI cancer. In some cases, genetic testing may help patients better understand their inherited risks.

Patients with higher risks of developing GI cancer may benefit from screening. Colorectal cancer screening, however, is recommended for everyone starting at age 45 (or earlier for patients with higher risks).

Addressing lifestyle habits by making healthy changes may benefit everyone and may lower a patient’s chance of getting GI cancer.