Just over 95,000 patients are diagnosed with colorectal cancers ever year, according to the American Cancer Society (ACS), and that’s a lot. Cancers that begin in the colon or rectum are America’s third most common type of malignancy, but the second leading cause of cancer deaths.
Thankfully, an emphasis on pro-active screening has led to a significant decline in mortality rates, both among men and women, over the last 3 decades. For either gender, the ACS recommends getting a preventive colonoscopy beginning at age 50, and going in for follow-up screenings every 10 years.
Colon Cancer Is Becoming More Common In Younger People
That’s been the party line on colorectal cancer for years. It’s a disease for old people, and only older patients need to be checked for it. New research has shown that the prevailing understanding of this cancer used to be true, but the situation is changing drastically.
Every year between 1992 and 2005, the incidence of colorectal cancer in young women grew by 1.6%. In men, it grew by 1.5%. Every year. Those results, published in the journal Cancer Epidemiology, Biomarkers & Prevention, were enough to shock the ACS researchers who discovered the rise.
Scientists, who rarely go for sensationalism, are calling the increase “incredible.” Meeting in December at Georgetown University’s Ruesch Center for the Cure of Gastrointestinal Cancers, a group of experts gathered to discuss the issue.
The results of that discussion were reported by Medscape, but the first thing to note is that no one really knows what’s going on. There are theories, and we’ll cover them in a minute, but researchers are still unclear as to why more young people are developing these cancers.
Have We Been Missing Cancers All Along?
One problem is that colorectal cancers are extraordinarily likely to be misdiagnosed, at least when younger patients are concerned. One speaker, Stephanie Guiffre, said an initial misdiagnosis may occur in up to 50% of cases. She cited 2 reasons to explain this:
- Young patients don’t know how to recognize the symptoms of colorectal cancer, and are thus less likely to turn to doctors.
- Doctors aren’t looking for symptoms in young people, so they don’t see them as reliably.
When colorectal cancer (CRC) is diagnosed in a young person, it’s often associated with a pre-existing genetic syndrome. Doctors are usually tipped off to the cancer by Lynch syndrome, which isn’t hard to believe, since the only defining characteristic of Lynch syndrome is an increased risk for certain cancers. But less than 25% of young adults diagnosed with CRC actually have Lynch syndrome. The other 75% have no genetic predisposition for the cancer, and no family history of the disease.
That fact hasn’t made its way down to practicing physicians. Oddly, Lynch syndrome usually causes colorectal tumors that grow on the right side of a patient’s colon. But in young patients, ones without a hereditary syndrome that would increase their risk for CRC, the tumors generally grow on the left. Quite literally, doctors might just be looking in the wrong place.
Misdiagnosis is a major problem here, but it doesn’t change the fact that way more young patients are getting colorectal cancer now than just 20 years in the past. So why is it happening?
Why Are Young People Getting Colorectal Cancer?
In their meeting at Georgetown, the experts proposed a number of theories to explain the increase. Specifically, they noted a few worrying societal trends that seem parallel to the rise in colorectal cancer diagnoses.
Among young patients (defined here as under the age of 50), rates of obesity and diabetes have risen over the past 3 decades at an alarming rate. Is there a causal link between obesity and colorectal cancer? Maybe, maybe not. But surgeon Tom Weber, MD, who spoke at the conference, told Medscape the “correlation is just impossible to overlook.”
Another trend is even more surprising. According to Weber, young adults in the US have stopped drinking milk, at least from the gallon jugs that people who grew up in the 50s and 60s used to consume the stuff. Younger people are opting for sugary drinks instead, and losing out on calcium, believed to lower the risk for CRC, in the process.
Other possibilities are drawn from known risk factors for adults, like drinking alcohol and consuming processed meats. Whether or not young adults are drinking more alcohol, and consuming more processed meat, than 30 years ago is an open question, but trends like that could be involved in the skyrocketing CRC numbers.