Colorectal Cancer: Symptoms and Risks
Cancer develops when abnormal cells grow out of control. These cells may invade nearby tissues and, in some cases, spread to other parts of the body.
Colorectal cancer is cancer that begins in the colon or rectum. The colon makes up most of the large intestine, while the rectum is the final part of the large intestine before the anus.
Excluding skin cancers, colorectal cancer is one of the most commonly diagnosed cancers in the United States. It affects both men and women, and the risk increases with age. Certain medical conditions, inherited conditions, family history, and lifestyle factors can also increase your risk.
Possible symptoms of colorectal cancer include blood in or on the stool, a persistent change in bowel habits such as diarrhea or constipation, a feeling that the bowel does not empty completely, ongoing abdominal pain or cramping, unexplained weight loss, and iron-deficiency anemia. Some people have no symptoms, especially in the early stages.
Many of these symptoms can be caused by conditions other than cancer. However, new or persistent symptoms should be discussed with your doctor, especially if you have other risk factors.
For adults at average risk, regular colorectal cancer screening should generally begin at age 45. Most adults should continue screening through age 75. People at increased risk may need to start earlier, be screened more often, or use a particular type of test.
Screening is intended for people who do not have symptoms. If you have possible symptoms of colorectal cancer, you should be evaluated rather than waiting for your next routine screening test.
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What increases the risk of colorectal cancer?
The exact cause of most colorectal cancers is not known, but several factors can increase the likelihood of developing the disease.
Some risk factors cannot be changed.
Age
The risk of colorectal cancer increases as you get older. However, colorectal cancer can also occur in younger adults, so concerning or persistent symptoms should not be ignored based on age alone.
Family and personal history
Having a close relative with colorectal cancer or certain colorectal polyps can increase your risk, particularly if that relative was diagnosed at a younger age.
Your risk may also be higher if you have previously had colorectal cancer or certain types of polyps.
Inflammatory bowel disease
Long-standing inflammatory bowel disease, such as Crohn's disease or ulcerative colitis, can increase the risk of colorectal cancer.
Inherited conditions
Certain inherited conditions can substantially increase colorectal cancer risk. These include Lynch syndrome and familial adenomatous polyposis, or FAP.
If you have a strong family history of colorectal cancer or an inherited cancer syndrome, your doctor may recommend earlier or more frequent screening.
Some risk factors can be changed.
Diet
A diet high in red and processed meats may increase colorectal cancer risk. Eating a balanced diet that includes fruits, vegetables, whole grains, and other sources of fiber may help support overall health.
Excess body weight
Being overweight or having obesity is associated with a higher risk of colorectal cancer. Maintaining a healthy weight may help lower your risk.
Physical inactivity
Regular physical activity may help reduce colorectal cancer risk. Aim to be active regularly based on your health and fitness level.
Smoking
Tobacco use increases the risk of several cancers, including colorectal cancer. If you smoke, quitting can improve your overall health and lower your cancer risk.
Alcohol
Drinking alcohol is associated with an increased risk of colorectal cancer. Limiting alcohol can help reduce this risk.
When should I see my doctor?
Contact your doctor if you develop possible symptoms of colorectal cancer, particularly if they are new, unexplained, or persistent.
Symptoms can include:
- Blood in or on the stool
- A change in bowel habits, such as persistent diarrhea or constipation
- Feeling that your bowel does not empty completely
- Ongoing abdominal pain or cramping
- Unexplained weight loss
- Unusual tiredness or weakness
- Iron-deficiency anemia
These symptoms are common and often have causes other than cancer, but they should still be evaluated.
Seek prompt medical attention for significant rectal bleeding, black or tarry stools, severe or worsening abdominal pain, dizziness or fainting, or other symptoms that suggest substantial bleeding or serious illness.
What will my doctor do?
Your doctor will ask about your symptoms, medical history, medications, and any personal or family history of colorectal cancer or polyps.
They may examine your abdomen and may perform a digital rectal exam.
Blood tests may be ordered to look for anemia or other abnormalities. Iron-deficiency anemia can sometimes occur when a colorectal cancer causes slow blood loss over time.
Depending on your symptoms and risk factors, your doctor may recommend additional tests. These may include a colonoscopy or imaging studies.
During a colonoscopy, a flexible tube with a small camera is used to examine the inside of the colon and rectum. If an abnormal area or growth is found, a tissue sample may be removed and examined under a microscope to determine whether cancer is present.
If colorectal cancer is diagnosed, additional testing may be needed to determine its stage, whether it has spread, and which treatments are most appropriate.
How is colorectal cancer treated?
Treatment depends on several factors, including whether the cancer begins in the colon or rectum, its stage, whether it has spread, the tumor's characteristics, your overall health, and your preferences.
Treatment may include:
- Surgery
- Chemotherapy
- Radiation therapy
- Targeted therapy
- Immunotherapy
Surgery is often the main treatment for early-stage colorectal cancer. It may involve removing the cancer along with a portion of the colon or rectum and nearby lymph nodes.
Chemotherapy uses medications to destroy cancer cells or stop them from growing. It may be given before or after surgery or used to treat cancer that has spread.
Radiation therapy uses high-energy radiation to destroy cancer cells. It is used more commonly for rectal cancer than for colon cancer.
Targeted therapies and immunotherapies may be options for some people, particularly when the cancer has spread or when testing shows that the tumor has specific genetic or molecular characteristics.
Treatment may aim to cure the cancer, reduce the chance that it will return, slow its growth, or relieve symptoms and improve quality of life.
Outlook varies widely and depends on factors such as the stage of the cancer when it is diagnosed, whether it has spread, the tumor's characteristics, overall health, and how well it responds to treatment. Colorectal cancer found at an earlier stage is generally easier to treat, which is one reason routine screening and evaluation of concerning symptoms are important.
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