Colorectal Cancer: What You Should Know
Bowel cancer is also called colorectal cancer and includes large bowel cancer (colon cancer) and cancer of the back passage (rectal cancer or cancer of the rectum). Find out about bowel cancer symptoms, risk factors, causes and preventing bowel cancer. There is information about tests to diagnose bowel cancer and treatments including surgery, chemotherapy, radiotherapy, biological therapy, research and clinical trials.
To understand colorectal cancer, it helps to know something about the structure of the digestive system and how it works.
After food is chewed and swallowed, it travels to the stomach. There it is partly broken down and sent to the small intestine. The small intestine is only called small because it isn’t very wide compared to the colon. In fact, the small intestine is the longest part of the digestive system — about 20 feet. The small intestine also breaks down the food and absorbs most of the nutrients.
What remains goes into the colon (large intestine), a muscular tube about 5 feet long. The colon absorbs water and nutrients from the food and also serves as a storage place for waste matter (stool). Stool moves from the colon into the rectum, which is the last 6 inches of the digestive system. From there, stool passes out of the body through the opening called the anus.
The colon begins at the end of the small intestine – on the right side of the body at a place called the cecum. It goes up (the ascending colon in the picture) and bends to go across the top of the belly (the transverse colon in the picture), and turns down again on the left side (the descending colon in the picture). The rectum is in the lower part of the pelvis.
Abnormal growths in the colon or rectum
Most colorectal cancers start as a polyp – a growth that starts in the inner lining of the colon or rectum and grows toward the center. Most polyps are not cancer. Only certain types of polyps (called adenomas) can become cancer. Taking out a polyp early, when it is small, may keep it from becoming cancer.
Over 95% of colon and rectal cancers are adenocarcinomas. These are cancers that start in gland cells, like the cells that line the inside of the colon and rectum. There are some other, more rare, types of tumors of the colon and rectum.
The information here is only for adenocarcinomas in the colon or rectum.
Colon cancer facts
- Colorectal cancer is a malignant tumor arising from the inner wall of the large intestine.
- Colorectal cancer is the third leading cause of cancer in males and fourth in females in the U.S.
- Risk factors for colorectal cancer include a family history of colorectal cancer,colon polyps, and long-standing ulcerative colitis.
- Most colorectal cancers develop from polyps. Removal of colon polyps can prevent colorectal cancer.
- Colon polyps and early cancer may have no symptoms. Therefore regular screening is important.
Colon Cancer Symptoms
Signs and symptoms of colon cancer tend not to be specific. In other words, the signs and symptoms can occur due to a number of different conditions. When colon cancer is detected in its early stages, it may not have even caused symptoms. Symptoms can also vary according to the specific location within the colon where the tumor is located.
Some symptoms and signs of colon cancer are:
- rectal bleeding or blood in the stool,
- dark-colored stool,
- change in bowel habits,
- change in stool consistency,
- constipation,
- diarrhea,
- narrow stools.
What are the risk factors for colorectal cancer?
While we do not know the exact cause of most colorectal cancers, there are certain known risk factors. A risk factor is something that affects a person’s chance of getting a disease. Some risk factors, like smoking, can be controlled. Others, such as a person’s age, can’t be changed.
But risk factors don’t tell us everything. Having a risk factor, or even several, does not mean that you will get the disease. And some people who get colorectal cancer may not have any known risk factors. Even if a person with colorectal cancer has a risk factor, it is often very hard to know what part that risk factor may have played in the development of the disease.
Researchers have found some risk factors that may increase a person’s chance of getting polyps or colorectal cancer.
Diagnosis:
- Diagnosis of colorectal cancer can be made by sigmoidoscopy or bycolonoscopy with biopsy confirmation of cancer tissue.
- Treatment of colorectal cancer depends on the location, size, and extent of cancer spread, as well as the health of the patient.
- Surgery is the most common treatment for colorectal cancer.
- Chemotherapy can extend life and improve quality of life for those who have had or are living with metastatic colorectal cancer. It can also reduce the risk of recurrence in patients found to have high-risk colon cancer findings at surgery.
Colorectal cancer usually starts from polyps or other precancerous growths in the rectum or the colon (large intestine). People with precancerous growths or signs of colorectal cancer don’t always show symptoms. That’s why screening is important—doctors can see and remove growths or suspicious tissue before they become cancerous.
Your risk for colorectal cancer increases if you:
- Smoke
- Have a history of inflammatory bowel disease, ulcerative colitis, or Crohn’s disease
- Have a family history of colorectal cancer
- Have a personal history of colorectal cancer or colon polyps
- Have certain genetic syndromes (for example, Lynch or FAP)
- Have diabetes
You should see your doctor also if you have any of these symptoms, even though they do not necessarily indicate colorectal cancer:
- A change in bowel habits (for example, diarrhea, constipation, feeling that the bowel does not empty all the way)
- Bright or dark blood in stool
- Stools narrower than usual
- Frequent gas pains, bloating, fullness, or cramps
- Weight loss for no known reason
- Feeling very tired
- Vomiting
When and how should I get screened?
You should begin getting screened at age 50 if you are at average risk of developing colorectal cancer. However, some people at higher risk for colon cancer may need to be screened earlier and some may need to undergo more frequent screening. Discuss with your doctor the best strategy for you. Here are several options:
- A colonoscopy— A doctor uses this thin tube with a light and lens to look inside the rectum and colon for growths, other abnormal tissue, or cancer. You will need to prepare for the test and will be sedated during it.
Routine screening: every 10 years. - Flexible sigmoidoscopy—A doctor uses a thin tube with a light and lens to look inside the rectum and lower third of the colon for growths, other abnormal areas tissues, or cancer. This thin tube may also include a tool for removing abnormal tissue for examination. You will need to prepare for the test.
Routine screening: every 5 years. - Fecal blood test (gFOBTor FIT test)—Using an at-home kit from your physician, you take a sample of your stool and return it to a lab, where it is checked for hidden blood, sometimes a sign of cancer. If blood is found, you will need a colonoscopy to find out why.
Routine screening: once a year. - Stool DNA test —Using an at-home kit from your physician, you take a sample of your stool and return it to a lab, where it is checked for blood as well as for genetic changes sometimes found in cancer and precancer cells. If the test is positive, you will need a colonoscopy.
Routine screening: every 3 years. - Computed tomography colonography or “virtual colonoscopy”—An X-ray imaging procedure that produces 2D and 3D views of the colon from the rectum to the lower end of the small intestine as well as some visualization of the small bowel. The colon will be gently and temporarily inflated with air through a thin tube tip placed in the rectum. You will need to prepare for the test.
Routine screening: every 5 years.
Remember to ask your doctor about colorectal cancer screening.
“Regular screening, beginning at age 50, is the key to preventing colorectal cancer,” said Alberto Gutierrez, Ph.D., an FDA expert on screening devices. “People at higher risk of developing colorectal cancer should begin screening at a younger age, and may need to be tested more frequently. Currently, individuals have several options for testing based on their risks and preferences. You should talk with your doctor to determine which screening program is right for you.”
What’s the good news?
More people who get the disease are surviving or are surviving longer with the help of screening, surgery and/or drugs approved for the treatment of patients with colorectal cancer. Because not all populations react the same way to every treatment, scientists are also developing “companion diagnostics,” tests to determine, for example, if a mutation in a particular gene found in tumors will render a drug effective, ineffective, or even harmful among certain groups.
Researchers study new ways to prevent, treat, and manage the disease. Patients who want to know about clinical trials—research studies that involve people—may want to discuss this option with those close to them and with their doctor.
How can I reduce my risk?
A number of factors may put you at risk for colorectal cancer: your age, medical history, race or ethnicity. But you can reduce that risk. Here’s how:
- Exercise regularly and vigorously
- Maintain a healthy diet (high in vegetables and fruits; low in red and processed meats)
- Maintain a healthy weight
- Limit the amount of alcohol you drink
- Don’t smoke and avoid second-hand smoke
