After decades of declining colon and rectal cancer rates, data published last week shows that these diseases have been increasing among young adults. Colon cancer rates have increased 2.4% annually among adults in their 20s and 1.0% among those in their 30s. For rectal cancer, the increase is even more dramatic: 3.2% among those in their 20s. For those born around 1990 the rates of colon cancer are more than two fold greater (2.4 times) than those born around 1950. Rectal cancer is over 4 fold greater (4.3 times) for those born around 1990 as compared to those born around 1950.
So the question, of course, is why the dramatic rise after decades of declining rates?
When I discuss colon and rectal cancer risks with patients, I often refer to two classic epidemiologic studies. The first study was done by Armstrong and Doll in 1975. It compared incidence and mortality rates for 27 cancers in 23 countries and correlated these with a variety of dietary habits and other variables. Dietary variables, particularly meat and animal protein consumption, was strongly associated with cancers of the colon and rectum. Further, these investigators confirmed prior data suggesting a protective effect of fiber consumption.
The second study to which I refer is actually an earlier study by Dennis Burkitt published in 1971. It was here that the idea that colon cancer could be linked to diet was first advanced. He reported that colorectal cancer was rare among rural Africans and this, he suggested, was because this population had little meat in their diet and instead ate a lot of fiber from fruits, grains, and vegetables.
Obesity and sedentary lifestyles are also associated with colorectal cancer, as are heavy alcohol use and chronic conditions like inflammatory bowel disease and Type 2 diabetes, all of which are on the rise. But experts are not entirely convinced these are the only reasons colorectal cancer is increasing among young people. “It is not surprising that the timing of the obesity epidemic parallels the rise in colorectal cancer because many behaviors thought to drive weight gain, such as unhealthy dietary patterns and sedentary lifestyles independently increase colorectal cancer risk,” the authors wrote.
Of particular concern with rising rates among those in their 30s and 40s is the fact that screening by colonoscopy is only recommended beginning at age 50 for people who are at average risk. The risk is higher among African-Americans, and the American College of Gastroenterology recommends they begin screening at 45.
In terms of advice, I generally stress that maintenance of a healthy weight, reduction of animal protein consumption, limiting alcohol intake and an increase in dietary fiber would also reduce one’s risk. More recently, a 2016 USC study showed that moderate coffee consumption, between one to two servings a day, was associated with a 26 percent reduction in the odds of developing colorectal cancer. Moreover, the risk of developing colorectal cancer continued to decrease to up to 50 percent when participants drank more than 2.5 servings of coffee each day. The indication of decreased risk was seen across all types of coffee, both caffeinated and decaffeinated.
At Santa Monica Primary Care, I have long recommended for my patients 40 and older, an adjunct screening test with a fecal occult blood test kit in which a stool sample is collected at home and mailed back into the office. Whereas this does not replace a colonoscopy in terms of detection, it does represent a relatively non-invasive way in which to begin screening sooner and also between years of colonoscopies. Positive results can be followed up with a colonoscopy. Today there is even a ‘virtual’ colonoscopy which is as accurate as a traditional optical colonoscopy and can be performed at an outpatient imaging center and does not require any anesthesia. With one third of new colorectal cancer cases being diagnosed in those under the age of 55, early initiation of already effective screening techniques simply make sense. Caught earlier, treatment options for colorectal cancers are more effective.