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Colorectal Cancer

Updated: Nov 19, 2023

Dr. Ken D. Nguyen is a gastroenterologist at Pacifica Digestive Health. He is also the President and was one of the co-founders of Pacifica Digestive Health. His clinical interests include screening and management of gastric cancer in Asian patients, viral hepatitis (including hepatitis B and hepatitis C), advanced liver disease and cirrhosis, colon cancer screening, and international medicine.

Pacifica Digestive Health Patient Education - Colorectal Cancer

What is Colorectal Cancer?

Colorectal cancer, which is also referred to as large bowel cancer, rectal cancer or colon cancer, affects the colon and the rectum. A cancer is an abnormal growth and in this case, it is located in the colon or rectum. It is more common as individuals get older. Just as with other cancer infections, it is best that you seek treatment as soon as it is recognized. Early treatment will prevent the cancer from reaching other areas of your body. Luckily, it is one of the few cancers that we have effective screening tests for which can pick up early cancer. Some tests are even able detect and remove the growths (polyps) before they turn into cancer. With the the recent changes in diet and lifestyle in recent decades in developed countries, there has been an increase in cancer cases.

What Are the Signs and Symptoms of Colorectal Cancer?

There are a number of signs and symptoms for colorectal cancer including changes in your bowel habits, diarrhea, constipation, fecal staining with blood, as well as pain and bloating in the abdomen. In addition, a feeling of being full even though you have not eaten, fatigue even after working very little, as well as unexplained weight loss may be signs of cancer. In the event that these signs and symptoms persist, it is best that you seek medical assistance quickly.

What Are Possible Causes and Risk Factors for Colorectal Cancer?

There are a few possible causes of colorectal cancer. First, the genes that may increase your risk for colorectal cancer may be inherited. Those with a family history of colorectal cancer cancer, as well as other cancer, may have an increased risk of having colorectal cancer. This is especially true if you have first-degree relatives (parents or siblings) who developed cancer before the age of 60 or if you have multiple distant relatives with colorectal cancer. If this is true, you should undergo a screening colonoscopy earlier than most people.

Other possible causes include eating poor diet and living an unhealthy lifestyle with lack of exercise. Eating unhealthy foods that have high fat content are have been linked to higher risk of colorectal cancer. Regular exercise and physical activities have been linked to a decreased risk of colorectal cancer. Therefore, it is recommended that you eat a healthier diet that is low on fat content as well as rich in green leafy vegetables and high fiber foods. Your diet should include whole grain foods, cereals, and healthy beverages such as fresh juices. A healthy and balanced diet may reduce your risk of developing colorectal cancer. Having regular exercise and staying physically active may reduce your chance of developing colorectal cancer.

There are several other known risk factors. Age is a known risk factor for colorectal cancer, especially those who are older than 50-years-old. African-American people also have a higher tendency to develop colorectal cancer. Having chronic inflammation of your colon, such as from longstanding inflammatory bowel disease (IBD) also increases your risk for colon polyps and colon cancer. And finally, men are more likely than women to develop colorectal cancer during their lifetime.

When Should You Start Screening for Colorectal Cancer?

For Average-Risk Patients

Most people are consider average-risk if they do not a family history of with colorectal cancer or any other risk factor, such as having IBD. For those with average-risk, there are currently multiple screening tests available that can detect colorectal cancer early and screening should started at the age of 50. If you are African-American, it is recommended that you start screening sooner at the age of 45. However, there has been new recommendations from various medical societies, including the American Cancer Society, that colorectal cancer screening should starting at age 45 for average-risk patients because of higher incidence of colorectal cancer in young people below the age of 50 being detected in recent years.

For High-Risk Patients

Family history of colorectal cancer: If you have a family history of colorectal cancer in a first-degree relative (i.e. mother, father, siblings) or in multiple second-degree relatives, you are considered to be high-risk. It is recommended that you undergo colorectal cancer screening 10 years before the age at which your relative was diagnosed with colorectal cancer. Colonoscopy is the screening method that is recommended for those with a family history of colorectal cancer. After a normal screening colonoscopy, you should continue to have a screening colonoscopy every 5 years.

Inflammatory bowel disease: Youare also considered to be high-risk if you have long-standing IBD, especially if you have pancolitis, which is inflammation of the entire colon. This is especially true if your colitis has been poorly controlled and difficult to manage. It is therefore recommended for you to undergo a screening colonoscopy starting 8 years after first being diagnosed with colitis. And if you have ulcerative colitis (UC) that has been complicated by primary sclerosing cholangitis (PSC), which is inflammation and scarring of the large bile ducts, colorectal cancer screening should be started immediately.

What Are the Screening Options for Colorectal Cancer (for Average-Risk Patients)?

Colonoscopy is a method of screening for colorectal cancer where the colon is directly visually using a colonoscope after it is cleaned out by a bowel prep. One possible benefit of colonoscopy compared to other screening test is that polyps can be detected and removed before they can progress towards cancer. And if you have an abnormal test using another screening method, you will eventually need a full colonoscopy. If you have average-risk and your colonoscopy exam is normal, you do not have to repeat it for another 10 years. If there were polyps found on your exam, you may need to have it repeated within 1 to 5 years depending on the type, size, and amount of polyps you had. Colonoscopy is the preferred screening method when available.

Fecal Immunochemical Test (FIT) and Fecal Occult Blood Test (FOBT) are both simple screening tests that can be done at home. They are both sensitive tests that can detect small amounts of blood in your stool, which may be a sign of colorectal cancer. If you have a abnormal FIT or FOBT test, you will need to undergo a diagnostic colonoscopy. If your test is normal then you will need to repeat the test annually.

Cologuard®, or stool DNA testing, is another at-home stool test similar to FIT or FOBT, but is only available by prescription. When your doctor orders it, it is mailed direct to you from the lab. You collect the stool sample and mail the test back to the lab. This test detects colorectal cancer by picking up genetic mutations in cancerous cells that are shed by colon cancer. Cologuard® is more sensitive than FIT and FOBT. Similar to FIT and FOBT, you will need to undergo a diagnostic colonoscopy if you have an abnormal Cologuard® test. Cologuard® is generally done every 3 years if the results remain normal.

What is the Treatment for Colorectal Cancer?

Treatment of colorectal cancer varies depending on the location in the colon where it is found, the size, and if it's spread beyond the colon to lymph nodes or other organs. In general, the treatment involves a combination of surgery and chemotherapy.


In conclusion, the rate colorectal cancer has increased over the last few decades in developed country due in part to poor diet and lifestyles changes. However, it's also one of the few cancers that has effective screening tests to detect early cancer which can be treated and possibly even cured. Colonoscopy is one of the screening tests that allows direct vision of the colon and removal polyps which may grow to cancer if left intact, and thus is the preferred screening method.

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