Colorectal cancer forms in either the colon, a five-foot section of the large intestine, or the rectum, which connects the colon to the anus and holds waste, called stool, before it is expelled.
Colon cancer and rectal cancer start the same way and share many risk factors and symptoms. The two are often referred to together as colorectal cancer. There are some significant differences between them, though.
Colon cancer that has not spread to distant parts of the body is usually treated with surgery, if feasible. If surgery is performed, doctors determine whether the patient needs additional treatments like chemotherapy.
Rectal cancer that has not spread to distant parts of the body is also treated with surgery. For some patients, radiation therapy and chemotherapy are used to decrease the risk of the cancer returning after treatment. In some cases, radiation therapy and chemotherapy can reduce the need for surgery. Rectal cancer surgery can be more complex than colon cancer surgery.
How does colorectal cancer start?
Colorectal cancer usually starts as a polyp. Polyps are small overgrowths in the tissue lining the colon or rectum. Polyps are not cancer.
Some polyps can turn into cancer over time. Most of these polyps are adenomas, which begin in mucus-producing gland cells that line the intestine and other organs. Adenomas are considered pre-cancerous growths.
It can take several years for an adenoma to develop into cancer. When it does, the cancer is called adenocarcinoma. This is the most common type of colorectal cancer.
There are other, rarer types of colorectal cancer, including colorectal neuroendocrine tumors and rectal cancers that involve the cells of the anus.
There are more than 150,000 colorectal cancer diagnoses in the U.S. each year. As of 2018, the disease’s five-year survival rate is about 65%. This figure does not include people diagnosed more recently, who could benefit from new treatments.
Young-onset colorectal cancer
Historically, most cases of colorectal cancer have been in people over age 55. In recent years, there has been an increase in diagnoses among people under age 55. MD Anderson’s Young-onset Colorectal Cancer Program offers specialized services for these patients. Services include fertility care, genetic testing and counseling, as well as support groups for young adults.
Colorectal cancer screening
Most precancerous polyps produce few, if any, symptoms. It is important to get screened regularly for colorectal cancer. Colorectal cancer screenings allow doctors to find and remove polyps before they turn into cancer. Screening can prevent most cases of colorectal cancer. It can also catch colorectal cancer early, when treatments are more likely to be successful.
- Learn more about colorectal cancer screenings
Colorectal cancer risk factors
Anything that increases your chance of getting colorectal cancer is a risk factor. Colorectal cancer risk factors include:
- Age: More than 75% of colorectal cancer cases are diagnosed in patients age 55 and older. The median age at diagnosis is 66 years old. However, the rate of colorectal cancer diagnosed in adults less than 55 years old has increased in recent years.
- Race: African Americans have the highest rate of colorectal cancer among all racial groups in the United States.
- Family history: People whose relatives have had colorectal cancer or colorectal polyps have an increased risk of colorectal cancer.
- Inflammatory bowel disease: Patients with conditions that include Crohn’s disease or chronic ulcerative colitis are more likely to develop colon cancer. Learn more about inflammatory bowel disease and colorectal cancer.
- Personal history of colorectal cancer or polyps: People who have previously had colorectal cancer or colon polyps are at an increased risk of developing colorectal cancer.
- Hereditary cancer syndromes: Some genetic changes can be inherited and increase your risk for certain types of cancer. Inherited syndromes including hereditary nonpolyposis colorectal cancer, or Lynch syndrome, and familial adenomatous polyposis may put you at higher risk for developing colorectal cancer. Learn more about hereditary cancer syndromes.
- Diet: A diet heavy in red meat, processed meats, or meats cooked at very high heat can increase a person’s colon cancer risk.
- Obesity: Obesity increases a person’s chance of developing many different diseases, including colorectal cancer.
- Sedentary lifestyle: A lack of movement and exercise is a risk factor for colorectal cancer.
- Tobacco: Tobacco use, including cigarettes and chewing tobacco, is a colorectal cancer risk factor.
- Drinking too much alcohol: Heavy drinkers are at an increased risk for colorectal cancer.
For patients concerned about inherited family syndromes that cause colorectal cancer, we offer advanced genetic testing and counseling to help understand your risk.
Colorectal cancer prevention
Lifestyle choices that may decrease your risk of getting colorectal cancer include:
- Regular screening tests
- Staying at a healthy weight
- Regular exercise
- Eating a healthy diet with lots of fruits and vegetables
- Avoiding cigarette smoking
- Drinking alcohol only in moderation
Colorectal cancer screening can detect cancer early, giving you the greatest chance for successful treatment. While colonoscopy is the gold standard for colorectal cancer screening, you may be wondering when you should get your first test.
We spoke with gastroenterologist Mazen Alasadi, M.D., about the recommended age for colonoscopies.
Most people should get their first colonoscopy at age 45
Current guidelines suggest that you should get your first colonoscopy at age 45 if you are at average risk for colorectal cancer. If no polyps are found during your initial colonoscopy, then you wouldn’t need your next colonoscopy for another 10 years.
Regular screenings are recommended from age 45 through 75.
High-risk groups should start screening earlier
Individuals at higher risk for colorectal cancer should begin getting a colonoscopy earlier than age 45.
If you have a first-degree relative (e.g., parent or sibling) with a history of colorectal cancer, you should get your first colonoscopy at age 40, or 10 years younger than the age at which the family member was diagnosed, whichever is earlier.
Other groups who may need a colonoscopy sooner include those with:
- inflammatory bowel disease or
- inherited genetic changes, such as Lynch syndrome and familial adenomatous polyposis (FAP). Colonoscopy screening for people with FAP can begin as early as age 10.
Consult your doctor about colorectal cancer screening after age 75
While colonoscopies are still recommended for some people older than 75, speak with your doctor to determine if you should continue colorectal cancer screening after age 75.
Your body changes as you age, and for some people, a colonoscopy after age 75 isn’t recommended.
“Having a colonoscopy at age 45 is different than having one at age 75,” says Alasadi. “We consider it on a case-by-case basis.”
For example, some individuals over age 75 want to have another colonoscopy because their doctor found precancerous polyps during their previous colonoscopy. Or a patient could have a family history of colorectal cancer.
Or maybe you’ve begun to develop colorectal cancer symptoms.
“Let’s say you’ve been doing fine and suddenly at age 76, you begin to notice blood in your stool,” says Alasadi. “We don’t know if this could be related to hemorrhoids, diverticulosis or colorectal cancer. We might recommend a colonoscopy, so we can determine the cause of the bleeding.”
Older patients are also more likely to have comorbidities, meaning they have two or more diseases or medical conditions at the same time. For example, a patient older than 75 with heart disease, high blood pressure, diabetes and on blood thinners would need to disclose these conditions as well as current medications to their doctor.
“If a patient is on blood thinners, they have to stop taking that medication before receiving a colonoscopy,” says Alasadi. “I always get this cleared by the patient’s cardiologist or hematologist before the procedure.”
There’s also a greater risk to older people while undergoing anesthesia, so it’s important to consider the anesthesia administered during a colonoscopy.
“We always discuss the risks and benefits of the colonoscopy with each patient,” says Alasadi. “Once we explain all of these things, the patient signs a consent form before we proceed with the colonoscopy.”
MD Anderson doesn’t recommend colorectal cancer screening for people older than 85.
“If you don’t have any more problems or symptoms, you don’t need to have any more colonoscopies,” says Alasadi.
Request an appointment at MD Anderson online or by calling 1-877-632-6789.
Why choose MD Anderson for your colorectal cancer treatment?
At MD Anderson's Gastrointestinal Center, your colorectal cancer treatment is personalized to provide the best outcomes, while focusing on your quality of life. We offer leading-edge treatments for colorectal cancer, including:
- advanced minimally invasive surgeries that provide successful treatment while helping you to recover more quickly.
- sphincter-preserving surgeries that can avoid the need for a colostomy bag.
- curative surgeries not available anywhere else for complex or advanced cancers through our multidisciplinary team of surgical experts.
Multidisciplinary Team Approach
Colorectal cancer treatment at MD Anderson is provided by a team of experts, including medical oncologists, surgeons, radiation oncologists, gastroenterologists, radiologists, clinical nurses and mid-level providers. They discuss your case and develop a treatment designed to attack your cancer while minimizing side effects.
Supplementing your clinical care, MD Anderson also provides nutrition counseling, pain management, psychological support, wound management and other services.
Younger patients can also receive specialized support through our Young-onset Colorectal Cancer Program. This program offers services like genetic counseling and testing, fertility preservation and young-adult support groups.
In addition, our advanced knowledge in cancer genetics can help diagnose and treat inherited family syndromes that may increase your risk of colorectal cancer. This expertise also helps us work with you to plan the most effective treatment for your specific condition.
For patients who have been successfully treated for colorectal cancer and are being monitored for recurrence, our tumor Intercept program also offers circulating tumor DNA testing. Patients may even be matched with clinical trials to monitor for or prevent the cancer’s return. This test can help doctors diagnose a recurrence long before it shows up in an imaging exam.
Leading-Edge Advancements
As one of the world’s largest cancer research centers, MD Anderson is a leading center for the investigation into new methods of colorectal cancer treatment and diagnosis. Through our clinical trials, this research can give patients access to treatments and procedures not found anywhere else.
And at MD Anderson you'll also be surrounded by the strength of one of the nation's largest and most experienced cancer centers. From support groups to counseling to integrative medicine care, we have all the services needed to treat not just the disease, but the whole person.
Be in touch with your body. If something feels new or weird, please don’t wait to see the doctor.
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