Open Accessibility Menu

Dr. Nathan Susnow: ‘Colorectal cancer is preventable.’

Dr. Nathan Susnow: ‘Colorectal cancer is preventable.’

Colorectal cancer (CRC) is a cancer that starts in the colon or rectum. Excluding skin cancers, it’s the third most common cancer diagnosed in men and women and the fourth leading cause of cancer-related deaths in the U.S. In Colorado, about 8,000 deaths from CRC are reported each year.

"Although CRC is common, and while it can be lethal, it is preventable in most cases.  Screening also helps find the cancer at an early stage, when treatment works best,” said gastroenterologist Nathan Susnow, MD with Gastroenterology of the Rockies during a free online health lecture. 

He explained factors that can increase the risk of colorectal cancer, lifestyle changes that can reduce the risk of colorectal cancer, and screenings that can detect and even prevent the cancer, including the latest advances in artificial intelligence (AI) technology using the GI Genius ™ to both increase detection and prevent cancer.


Watch "Colorectal cancer—The preventable killer"


Signs of CRC

Dr. Susnow recommends that if you notice symptoms or signs that are concerning you should consult with your primary care provider or a gastroenterologist. He noted that these could include:

  • changes in bowel habits,
  • blood in the stool,
  • changes in shape or character of the stool,
  • unexplained weight loss,
  • challenges with abdominal pain and/or
  • anemia (that may be noticed in your annual labs)–this is a low blood count that may be accompanied by fatigue.

How CRC develops 

“CRC develops from small pre-cancerous pieces of tissue. These are called polyps," said Dr. Susnow. 

Dr. Susnow described the progression of a polyp, also called an “adenoma,” from a small pre-cancerous bump to a larger polyp that may have some cancer and, finally, as the polyp progresses into deeper tissue to a true cancer. 

He noted, “This process takes about 10 to 15 years for a pre-cancerous polyp to advance to a cancerous stage, called the adenoma to carcinoma sequence."

CRC Risk Factors

Risk factors include:

  • Country of origin (as it relates to diet and genetics)
  • Age (screening starting at age 45)
  • Sex (men are at a slightly higher risk, although throughout a lifetime, with women living longer, the risk evens out)
  • Race/Ethnicity (this has evened out among race and ethnicity with rates increasing among younger patients)
  • Socioeconomic status (as it relates to diet)
  • Family history (if you’ve relatives that have experienced CRC your risk increases, and it may be necessary to be tested earlier and more frequently. A colonoscopy is the recommended procedure.)

Lifestyle factors also contribute to CRC:

  • Obesity
  • Low physical activity
  • Smoking
  • Alcohol—There’s no healthy amount recommended any more.
  • Diet 
    • Eating red meat (including pork) and/or processed meat 
    • Eating food low in fiber 
    • Not eating enough fruits and vegetables
    • Eating charred, broiled, and grilled foods
    • Eating ultra-processed foods

“All of these factors increase your risk of CRC,” said Dr. Susnow. He did add however, “Diet and lifestyle are two areas that we can adjust to reduce our risk of CRC. The most beneficial diets are the Mediterranean and plant-based diets. And of course, everything in moderation is a good rule to follow.”

When to start screenings

“The biggest risk factor for CRC is not having any type of screening and not starting at age 45,” said Dr. Susnow. “We now recommend that patients begin their screenings at age 45, and they continue to age 75 or 85. While CRC overall has decreased in the last 40 years for patients over 50, in part due to CRC screenings, it has increased in those who are younger than 50,” said Dr. Susnow. He added, “It is thought that this uptick in younger patients is related to diet, increased exposure to ultra processed foods, a more sedentary lifestyle and increasing rates of obesity."

Screening, prevention and early detection

“Ideally,” said Dr. Susnow, “we want to identify polyps and cancers as early as possible." He said there are three screening options:

  • Stool tests allow for early detection primarily of CRC and for some larger polyps. There are two types: 
    • The FIT (fecal immunochemical testing) test. This looks for blood in your stool. 
    • ColoGuard is a DNA test that detects cancer cells and/or blood in the stool.

      “If the test results from either of these tests are positive, your next step will be to get a colonoscopy,” said Dr. Susnow.
  • A colonoscopy is a 30-minute procedure. It uses a high definition (HD) colonoscope, inserted into the colon, to enable physicians to identify any abnormalities, remove polyps before they advance to a cancerous stage and to remove some more complex polyps.

    Dr. Susnow noted, “A colonoscopy is the most effective colorectal cancer prevention exam. It can find precancerous polyps that can be removed before they turn into cancer. As we look at polyps, we can often determine if they’re concerning or not, and we are able to easily remove them to prevent cancer from occurring."

    A colonoscopy:
    • detects 3x more advanced lesions than FIT exams,
    • 2x more advanced lesions than FIT-DNA (ColoGaurd) exams,
    • is the only test that includes polyp removal at the time of the exam,
    • risk is minimal, and
    • it needs to only be performed every 10-years intervals, significantly less often than other exams.

      “Gastroenterology of the Rockies is the first practice in Colorado and one of the first in the country to incorporate GI Genius/AI technology into their colonoscopy exam,” said Dr. Susnow. 

      He added, “GI Genius significantly improves polyp detection and improves cancer detection as well. In fact, with GI Genius we increased the rate of polyp detection by 6.5%. For every 1% percent increase in adenoma detection rate results in a 3% decreased risk of CRC.”
  • A computed tomography (CT) colonography is for selected patients who would not be a good fit for a colonoscopy, but it is not typically recommended. This is an image scan that doesn’t require a scope. It does still require colon prep, so you do still need to clean out your colon. Dr. Susnow, explained, “To make this test cost effective, small polyps are ignored that would typically be removed during a colonoscopy. Also, if the result is positive, you would still need a colonoscopy."
  • Flexible sigmoidoscopy is much like colonoscopy, but looks at only part of the colon and rectum. If polyps are found, they may be removed during the test, or you may need to have a colonoscopy later. Bowel prep may be required, but is not as extensive as the one used for colonoscopy. Most people do not need to be sedated during this test. If polyps or suspicious areas are seen, a colonoscopy will be needed to look at the rest of the colon. Flexible sigmoidoscopy must be done every 5 years and should be combined with FIT or FIT/DNA.

Schedule an Appointment

Call 720-853-3771 or visit to schedule a consultation with Dr. Susnow.

Click here to view/download Dr. Susnow's lecture slides.

Want to receive notification of special events and lectures?

Sign up to receive email notifications.