Colorectal Cancer Facts
Colorectal Cancer Facts
What is colorectal cancer?
Colorectal cancer is a cancer that starts in the colon or rectum, the final sections of the large intestine. You may also hear colorectal cancer called colon cancer or rectal cancer, depending on where the cancer begins.
Cancer develops when cells in the body begin to grow out of control. Normally, cells grow, copy themselves, and die in an organized way. In colorectal cancer, cells in the lining of the colon or rectum develop changes that allow them to continue growing and eventually form a tumor.
THE BASICS: Most colorectal cancers start as small growths called polyps. While most polyps do not become cancer, certain types can develop into cancer over time. Finding and removing these polyps through colorectal cancer screening can help prevent colorectal cancer or lead to early detection when cancer may be easier to treat.
What are the colon and rectum?
The colon and rectum make up the large intestine, which is the last part of your digestive system. After food is digested in the stomach and small intestine, the remaining material passes into the colon.
The colon absorbs water and salts from this material, turning it into stool. The rectum is the final 6 inches of the large intestine and stores stool until it leaves the body.
Together, the colon and rectum are about 5 feet long. The colon has four main sections:
Ascending colon (right side)
Transverse colon (across the abdomen)
Descending colon (left side)
Sigmoid colon (lower left, connecting to the rectum)
How does colon cancer start?
Most colorectal cancers begin as polyps, which are small growths on the inner lining of the colon or rectum. Adenomatous polyps, also called adenomas, are especially important because some can eventually become cancerous.
For most, the change from a polyp to colorectal cancer happens over many years. This gives doctors an opportunity to find and remove precancerous polyps during screening before cancer develops.
Some people have inherited conditions that cause large numbers of polyps and greatly increase colorectal cancer risk. One example is familial adenomatous polyposis (FAP), which is caused by an inherited genetic change.
What are the risk factors for colorectal cancer?
Anyone can develop colorectal cancer, but certain risk factors can increase your chances. Risk generally increases with age, although colorectal cancer can occur in younger adults.
Other risk factors include a personal or family history of colorectal cancer or certain polyps, inherited conditions such as Lynch syndrome or familial adenomatous polyposis, and inflammatory bowel disease, including Crohn’s disease and ulcerative colitis.
Some lifestyle factors may also affect colorectal cancer risk. Learning about your personal risk can help you and your healthcare provider decide when screening should begin and how often it may be needed.
What are the symptoms of colorectal cancer?
Colorectal cancer may not cause noticeable symptoms when it first develops, which is one reason regular screening is important. When symptoms do occur, they can vary depending on the tumor's size and location.
Possible symptoms include changes in bowel habits, blood in or on the stool, persistent abdominal pain or cramping, fatigue, weakness, and unexplained weight loss. These symptoms can also be caused by conditions other than cancer, but persistent or concerning changes should be discussed with a healthcare provider.
How does colorectal cancer affect the body?
As colorectal cancer grows, it can affect the digestive system, blood, and eventually other parts of the body.
How colorectal cancer affects the digestive system
A tumor in the colon or rectum can narrow or block the bowel. This may cause constipation, diarrhea, abdominal pain or cramping, blood in the stool, or a feeling that the bowel does not completely empty.
How colorectal cancer affects the blood
Colorectal tumors can bleed slowly over time. This blood loss may lead to anemia, or a low red blood cell count, which can cause fatigue, weakness, dizziness, or shortness of breath.
How colorectal cancer affects other organs
When colorectal cancer spreads to another part of the body, it is called metastatic colorectal cancer. The most common sites of spread include the liver, lungs, and lymph nodes. Metastatic disease may cause additional symptoms depending on which organs are affected.
What are the stages of colorectal cancer?
Colorectal cancer is generally grouped into stages 0 through IV based on how far the cancer has grown or spread.
Stage 0 and stage I are limited to the inner layers of the colon or rectum or have grown into the bowel wall. Stage II has grown through the bowel wall but has not spread to nearby lymph nodes. Stage III has spread to nearby lymph nodes. Stage IV has spread to distant parts of the body, such as the liver or lungs.
The stage of the cancer, along with its location, molecular features, and a person's overall health, helps the care team determine which treatments may be appropriate.
How is colorectal cancer treated?
Colon cancer treatment and rectal cancer treatment depend on the location and stage of the cancer as well as the tumor's specific characteristics. Treatment may include surgery, chemotherapy, radiation therapy, targeted therapy, immunotherapy, or a combination of approaches.
For some patients, clinical trials may provide access to new treatment approaches that researchers are studying. Your cancer care team can help explain your treatment options and whether a clinical trial may be appropriate.
Why is colorectal cancer screening important?
Colorectal cancer is a common cancer, but screening provides an opportunity to find precancerous polyps before they become cancer or identify cancer at an earlier stage.
Several colorectal cancer screening options are available, including stool-based tests and visual exams such as colonoscopy. The right screening approach depends on factors such as age, medical history, family history, and individual risk.
According to the American Cancer Society, people at average risk should begin regular colorectal cancer screening at age 45. People with certain risk factors may need to start earlier or be screened more frequently.
Regular screening is an important part of colorectal cancer prevention and early detection.
Types of colorectal cancer
About 95% of colorectal cancers are adenocarcinomas, which begin in gland-forming cells lining the inside of the colon and rectum.
Less common types include:
Neuroendocrine tumors, which begin in neuroendocrine cells of the digestive tract
Gastrointestinal stromal tumors (GISTs), which begin in specialized cells in the gastrointestinal tract
Lymphomas, cancers of immune system cells that can occasionally develop in the colon or rectum
Sarcomas, rare cancers that can develop in connective tissues of the colon or rectum
Related cancers
Colorectal cancer belongs to a larger group of gastrointestinal (GI) cancers. Other GI cancers include stomach cancer, small intestine cancer, esophageal cancer, pancreatic cancer, and anal cancer.
Some inherited cancer syndromes can increase the risk of colorectal cancer as well as other cancers. For example, people with Lynch syndrome have an increased risk of colorectal cancer and several other cancer types.