Colorectal Cancer Awareness Month: Surgeon talks prevention, screening

This Colorectal Cancer Awareness Month, we’re celebrating.

We’re celebrating 940,000 lives saved between 1975 and 2020, thanks to more screening and better treatments for colorectal cancer.

Overall, rates of colorectal cancer have been decreasing since the 1980s.

Still, there is work to do. Colorectal cancer remains the third most common cancer diagnosed in both men and women. For men, it is the third most common cause of cancer death, and for women, it is the fourth most common cause of cancer death. And rates of colorectal cancer have been increasing among adults under 50.

Thomas Curran, M.D., a colorectal cancer surgeon, sat down for a Q&A on the latest in colorectal cancer screening, diagnosis and prevention.

Q: Let’s start with the basics. Why is it important to get screened for colorectal cancer?

A: Really, there are two pieces of information. One is that colorectal cancer is quite common. Relatively recent figures from the American Cancer Society suggest that over the course of an American's lifetime, the likelihood of being affected by colon or rectal cancer is around 4%, or one out of 25. So it is pretty common.

The next thing is that it is a disease that, unfortunately, may not cause symptoms until it is quite advanced. That's where screening comes into play because many people may not know they have it, and if you wait until the development of symptoms – you're seeing blood in your stool or you're having unintentional weight loss or abdominal pain – at that point, the cancer may be advanced and treatment options may be more limited.

Q: So what are the screening options?

A: From the point of view of the United States Preventive Services Task Force, they embrace what they refer to as a “menu of options,” and that, broadly speaking, has three categories of tests.

One: endoscopic tests like colonoscopy. Two: stool-based tests like Cologuard or something called FIT testing, which is fecal immunohistochemical testing. And third is imaging-based tests.

Age to begin screening (average-risk individual): 45

Types of Colon Cancer Screening

Colonoscopy: every 10 years
Uses endoscope to look inside the colon.

Fecal immunochemical test (FIT): annually
Uses antibodies to look for hidden blood in the stool.

Multi-targeted stool DNA test: Every three years
Looks for changes to the DNA.

Colonoscopy has the highest sensitivity and specificity, meaning it's the most accurate for detecting colorectal cancer. It is the test against which all other tests are measured.

It also is by far the best test to identify precancerous lesions – to find polyps before they can become a cancer and remove them. So it has this kind of elevated place among the screening options because it is the most accurate for cancer. It is the most accurate by far for precancerous lesions, and it is the only test that has the ability to remove precancerous lesions to prevent the development of cancer.

Stool-based tests are also quite accurate for detecting cancer. They also make colorectal cancer screening more accessible – you don’t have to do the bowel prep that you have to do with colonoscopy, and you don’t have to take a day off work, drive to a facility and then have someone drive you home afterward because of the anesthesia.

For average-risk patients, stool-based tests should be done every one to three years, depending on the particular test, and colonoscopies every 10 years. Some people will get recommendations for more frequent screening depending on their individual situations.

CT colonography is a noninvasive approach that uses a CT scanner to get images of the large intestine. You do need to do bowel prep and come into the facility, although you won’t need anesthesia. We usually recommend this method only for people who aren’t a good fit for either colonoscopy or stool-based tests.

Q: What about other screening methods? Is there anything new?

A: The use of blood tests as screening for colorectal cancer has been looked at as a kind of Holy Grail for years. As I mentioned before, there are some inconveniences and challenges with colonoscopy, whereas a blood test is going to be quite a bit more convenient for most people.

In summer of 2024, there was a publication of a very large clinical trial in the New England Journal of Medicine on a blood test to detect the presence of colorectal cancer. They looked at almost 8,000 people who gave a blood specimen and then had a colonoscopy, and they found that the sensitivity (how effective the blood test was in identifying colon cancer) was high, 83%, and false positives were pretty low.

That test, called Shield, was FDA-approved in 2024. I think it is something that is on the horizon as an exciting technology that perhaps could play a big role in reaching more people for colorectal cancer screening.

Now, the drawback is that it is not so effective at finding precancerous lesions, or polyps. It had only 13% sensitivity for detecting advanced precancerous lesions. So it is very good at finding cancer, but it is a less useful tool for preventing cancer.

Q: We’ve heard a lot about an increase in colorectal cancer in younger adults. What can you tell us about that?

A: The age to begin colorectal cancer screening was historically 50. But in response to the trends that we’ve observed in the last 10 to 15 years of younger adults being diagnosed, the age to begin screening was changed to 45. To put a number on it, we have observed a 15% increase in colorectal cancer for patients in their 40s from the early 2000s to the 2010s.

We still do see that there are some people who develop colorectal cancer even earlier than the screening age. It remains uncommon, but it is much more common than it used to be, so I think it has truly changed the way that we practice.

Fifteen years ago, if someone in their 20s or early 30s came into the office and said they're seeing blood with their bowel movements, most of the time, people would just say, ‘OK. That's probably just hemorrhoids. Don’t worry about it.’

But more recently, in light of these trends that we've seen, we take those complaints very seriously and will frequently evaluate them with colonoscopy.

Q: Is there anything else of interest happening in the field of colon cancer detection?

A: There are some exciting technologies on the horizon. An interesting one is the role of artificial intelligence to augment colonoscopy. There are some tools that can be used during a colonoscopy where the AI in real time will draw attention to areas that it thinks look like a polyp.

This is a newer technology, and it’s still being improved, but it's something that I think we're going to see more and more of – this augmentation of our existing tools to perform screening more effectively.

I do colonoscopies both at MUSC and at the VA (Ralph H. Johnson VA Health Care System), and I have used it at the VA. I would say it's a technology that is in evolution. There's a lot of potential. As to whether it truly moves the needle on saving more lives and identifying more cancers, I think time will tell that.

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