Colon Cancer: We Must Do Better
New screening approaches combine better risk assessment, use of non-invasive testing, and more targeted colonoscopy.
Today, we look at a proposed shift in how we screen for colorectal cancer in the United States. I’ll start with the problem’s scope before turning to newer approaches to screening for colon and rectal cancer. Colon and rectal cancer are common and too often deadly. Your chances of getting colorectal cancer are influenced by your genetics and by environmental factors.
Risk factors are things that increase your chances of getting a disease such as cancer. They can be changeable or fixed (think family history). Risk factors that may be modified include:
- unhealthy diet (some say watch the processed foods and red meat; I say that we have only observational studies; at least two randomized trials show no increase in risk; I try to keep my red meat consumption modest)
These three factors alone may account for a third to a half of the colorectal cancer burden. Other factors include physical activity and heavy alcohol consumption. If you consume alcohol, the American Cancer Society recommends that you consume no more than one (for women) to two (men) standard drinks daily.
You cannot change factors include being older, having a personal history of colorectal cancer or polyps, ulcerative colitis or Crohn’s disease, a family history of colon cancer, or adenomatous polyps.
Also, if you have type 2 diabetes, you have an increased risk for colorectal cancer. On the plus side, such individuals appear to have a more favorable prognosis (on average) if they get colorectal cancer. Finally, emerging research points to a possible increase in risk among night shift workers.
There are significant differences in incidence by geography. Worldwide, colorectal cancer is the second most common cancer among women and the third most common among men. There are approximately 1.8 million cases annually, and over 850,000 deaths. In the United States, nearly 150,000 will be found with colon or rectal cancer this year, with just over two-thirds being in the colon (large bowel). The remainder starts in the rectum.
The global variation in colorectal cancer incidence is stunning, with regional variation over 10-fold. The risk appears highest in Australia, New Zealand, Europe, and North America. The lowest rates are in Africa and South-Central Asia.
It’s not just older folks
I noted that older age is a risk factor. Indeed, colon cancer is relatively uncommon before age 40. The incidence begins to rise with each decade beyond that. More recently, in the United States and some other Western countries, rates are rising for those under age 50.
In fact, in my home country of the USA, we have seen a two percent annual increase from 1995 through 2016. And while the incidence remains low for those 20 to 39, it may also be rising. The reasons for these disturbing trends remain unclear. While mortality is dropping overall here, it is growing among those 20 to 54. This increase appears limited to white individuals.
A growing body of evidence points to aspirin (and similar drugs) as protective against colon cancer. Regular use may drop risk by upwards of 20 to 40 percent. One example: The Prostate, Lung, Colorectal, and Ovarian screening trial found that aspirin use thrice-weekly dropped mortality from all causes (by a fifth) and colorectal cancer by nearly a third (29 percent). We don’t fully understand how it accomplishes this improvement, nor the minimal dose or duration. I would not start taking aspirin for colon cancer risk reduction without a dialog with your doctor.
Screening: We can do better
Colonoscopy is a gold standard for colorectal cancer screening. While effective, there is are associated issues. These include cost, access, and the fact that we fall short of screening the population. Currently, we do not test one-third of Americans.
Well, the American Gastroenterological Association (AGA) just fired a shot across the bow. It proposes a more targeted screening approach that better examines an individual’s risk of colorectal cancer. This newer way would use more non-invasive testing (such as stool testing) and more targeted colonoscopy referrals.
By taking this approach, we can increase compliance with screening, with a resultant increase in the number of lives saved. In my hospital, we put elective procedures such as colonoscopy on hold during the height of the Covid-19 pandemic. One study showed that the number of procedures dropped by 90 percent in America at the peak of the novel coronavirus crisis.
We must do better.
Here are the AGA’s changes in its white paper, “Roadmap for the Future of Colorectal Cancer Screening in the United States.” Publishing online, the expert panel proposes:
- Integration of alternative testing means to colonoscopy into organized screening programs.
- Rather than offering colonoscopy as the default for all, it should initially be provided only to those at high risk, increasing access for those who would benefit most.
- For those at lower risk, non-invasive screening (such as stool tests looking for blood) could be offered initially for those at average risk.
- Developing more accurate non-invasive tests.
The goal? Cheaper, accurate, and convenient testing, with test type based on an individual’s risk. We know that screening drops the odds of colon cancer death in the population by more than 50 percent.
I’m Dr. Michael Hunter. Thank you for joining me today.