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How to Detect Colon Cancer Early

Contributor James Cusack, MD
9 minute read
A doctor and patient discuss something displayed on a tablet screen.

Many people consider colon cancer to be a disease that affects older people. But it is becoming alarmingly more common in people younger than 50, even affecting those in their 20s and 30s. And younger adults are dying from the disease more often than in the past.

Adults of all ages should take steps to prevent colon cancer and detect it early. This makes treatment more effective, says James Cusack, MD, a Mass General Cancer Center surgical oncologist. Dr. Cusack is surgical director of the Center for Young Adult Colorectal Cancer. He implores younger adults to be more aware and proactive.

“As we get older, it’s important to recognize that we’re not invincible. And there’s an increasing likelihood of having a variety of different illnesses that are associated with increasing age. The concern is that these diseases — which we’ve typically associated with patients in their 50s or 60s or older — are now occurring in patients who are much younger,” he says. “Cancer is something that a young person is typically not prepared to even think about at such a young age. However, the reality is that colorectal cancer is increasing in incidence in young patients.”

Preventing colon cancer

You can take several steps to help prevent colon cancer and rectal cancer, collectively known as colorectal cancer, Dr. Cusack says. And these same lifestyle choices can also ward off many other types of disease:

  • Eat a healthful diet containing plenty of veggies, fruits, and whole grains.

  • Exercise regularly.

  • Limit or avoid alcohol.

  • Manage your weight so it stays in a healthy range.

  • Quit smoking — or better yet, don’t ever start.

  • Understand and follow the recommendations for cancer screening, which can detect cancer before you have symptoms or advanced disease.

The most important thing is to advocate on your own behalf if you have symptoms to make sure that your concerns are being addressed. If you have new symptoms, tell your primary care provider. You should have testing to diagnose any underlying condition and get treatment as early as possible.

James Cusack, MD
Surgical Oncologist
Mass General Cancer Center

Recognizing possible signs of colon cancer

Cancer is often a silent disease, and patients may not experience any symptoms until colorectal cancer progresses significantly from a polyp to an established tumor.

Dr. Cusack encourages people to report any changes in bowel habits to a health care provider:

  • Abdominal (belly) discomfort or cramping

  • Bleeding from your rectum or blood in your stool

  • Changes in the way stool looks or how often you move your bowels

  • Diarrhea, constipation, or a feeling that you can’t completely empty your bowel

  • Increased flatulence (gas)

  • Unexplained weight loss

“These symptoms are common, and they can be attributed to other things. Therefore, they may be ignored,” Dr. Cusack says. “The most important thing is to advocate on your own behalf if you have symptoms to make sure that your concerns are being addressed. If you have new symptoms, tell your primary care provider. You should have testing to diagnose any underlying condition and get treatment as early as possible.”

Colon cancer screening guidelines

Because colorectal cancer can occur in anyone and may not cause symptoms, everyone should be checked, Dr. Cusack emphasizes. Many medical societies and health care agencies have recently updated their recommendations to screen adults at younger ages.

According to the American Cancer Society, men and women should start screening to detect colorectal cancer at age 45 and continue through age 75. “After age 75, screening decisions should be made on a case-by-case basis, taking into consideration the overall health of the patient and life expectancy,” Dr. Cusack explains.

However, people with increased risk of colon cancer should be screened even earlier, as recommended by their health care providers. Risk factors include:

  • Family history of colorectal cancer

  • Hereditary colorectal cancer syndrome, such as Lynch syndrome (hereditary non-polyposis colon cancer or HNPCC)

  • Personal history of colorectal cancer, polyps, inflammatory bowel disease (for example, Crohn’s disease or ulcerative colitis)

  • Previous radiation to your abdomen or pelvis for prior cancer

But Dr. Cusack cautions that everyone must take screening seriously, not just those with risk factors.

“The majority of patients who are diagnosed with colorectal cancer do not have any preexisting personal risk factors or family history of colorectal cancer, so all individuals should be aware of colon cancer, including young adults,” he says. He recommends that you ask your doctor when to get a colonoscopy or other screening tests.

Colorectal cancer screening tests

Screening can identify precancerous polyps that may be removed before they become colon cancer. Early detection of cancer leads to a better prognosis. For people who are nervous about the tests, Dr. Cusack assures them that there are many options and improvements.

“We have invasive and noninvasive techniques for early detection of precancerous polyps and colon cancer. These include fecal occult blood test, colonoscopy, virtual colonoscopy, and DNA stool test. If you are concerned about discomfort, that should not deter you from getting some form of screening,” Dr. Cusack says.

Stool tests for colorectal cancer

Colorectal polyps and tumors tend to bleed, and the blood may be detected in stool. There is often not enough blood to see with the naked eye. But a simple test on a sample of feces can detect small traces of blood.

You can do a stool test at home or in a medical clinic. Your health care provider gives you items to collect a tiny sample of stool, such as a brush or tube. The sample is then tested in a lab. If the test detects any blood, you’ll need a more advanced test to find the source of the bleeding. Some tests also test stool samples for abnormal DNA that may indicate possible colon cancer.


Colonoscopy is a more invasive procedure. However, it is the most comprehensive means to detect and biopsy or remove colon polyps and cancer.

Before a colonoscopy, you have to prepare (clean) your intestines. This involves drinking a special liquid that empties all of the bowel contents. You also may need sedation for the procedure.

During the test, a health care provider inserts a tube into your anus and rectum, through your lower intestine and into your colon. The tube has a tiny light and camera on the end. Your health care provider can visualize polyps or tumors and remove polyps or take a sample of tissue.

“Colonoscopy is unsurpassed for screening of colorectal cancer,” Dr. Cusack says. “It is a very sensitive tool for the detection of small polyps and colon cancers and is the gold standard for screening.”

Other colon cancer testing options

Although colonoscopy is the most accurate, comprehensive option, some individuals may request noninvasive alternatives to detect colon cancer. Dr. Cusack suggests that they consider another screening option: virtual colonoscopy, also called CT colonography.

CT colonography is an advanced kind of computed tomography (CT) scan that produces three-dimensional images of your colon. It can be performed without bowel prep and avoids the discomfort that may be associated with colonoscopy. However, CT colonography is slightly less sensitive and does not permit removal of polyps or tissue sampling. If this test detects a polyp, your doctor will then recommend a colonoscopy to remove it.

Blood tests in conjunction with other colorectal cancer screening

New technologies are being developed that can detect tumor byproducts that may be present in stool or circulating in your blood. Tests to detect tumor DNA in stool are approved as alternatives to colonoscopy for colorectal cancer screening. The blood tests, often called biomarker tests, are currently approved for use along with other screening techniques such as colonoscopy.

Center for Young Adult Colorectal Cancer

In response to the alarming rise of colorectal cancers among younger adults, Mass General has created a specialized program. The Center for Young Adult Colorectal Cancer is dedicated to both research and clinical care.

Researchers work to understand the reasons behind this trend. Multidisciplinary teams address the unique concerns of younger adults diagnosed with the disease, including:

  • Advanced treatment options

  • Balancing parenting and work with a cancer diagnosis

  • Fertility concerns

  • Sexual health

Colorectal cancer is preventable and, in most cases curable, especially if it’s detected early, Dr. Cusack says. “Our biggest opportunity for saving patients’ lives and curing them is to detect colon cancer and treat it as early as possible.”


Surgical Oncologist