A study led by American Cancer Society researchers finds that new cases of colon cancer and rectal cancer are occurring at an increasing rate among young and middle-aged adults in the US. Once age is taken into account, those born in 1990 have double the risk of colon cancer and quadruple the risk of rectal cancer compared to people born around 1950, when risk was lowest.
The study was published February 28 in the Journal of the National Cancer Institute.
Overall, when all ages are combined, the rate at which new colon and rectal cancer cases are diagnosed has been dropping in the US since the mid-1980s. That decrease has been even steeper in the past decade, in large part due to screening – testing that can find colon or rectal cancer earlier, when it’s easier to treat. In some cases, screening finds growths called polyps that can be removed before they become cancer.
But the drop has been driven by older adults. During this same time, incidence rates have been increasing for adults under age 50, the age at which people at average risk are recommended to begin screening.
A closer look
The American Cancer Society researchers took a closer look at this trend by studying incidence rates by 5-year age groups and by year of birth. They looked at the records of almost 500,000 people 20 years and older who were diagnosed with colon or rectal cancer from 1974 through 2013. The data came from the Surveillance, Epidemiology, and End Results (SEER) program registries of people diagnosed with cancer. They included people born in 1890 through those born in 1990.
The study found that for adults ages 20 to 39, colon cancer incidence rates increased by 1% to 2% per year through 2013. In adults 40 to 54, rates increased by 0.5% to 1% per year from the mid-1990s through 2013.
Rectal cancer incidence rates have been increasing even longer and faster than colon cancer, rising about 3% per year from 1974 to 2013 in adults ages 20 to 29 and from 1980 to 2013 in adults ages 30 to 39. In adults ages 40 to 54, rectal cancer rates increased by 2% per year from the 1990s to 2013.
Rebecca Siegel, MPH, Strategic Director of Surveillance Information Services in the Intramural Research Department at the American Cancer Society says the increase in colon and rectal cancer among young age groups is concerning because it affects people during their most productive years.
“Trends in young people are a bellwether for the future disease burden,” said Siegel. “Our finding that colorectal cancer risk for millennials has escalated back to the level of those born in the late 1800s is very sobering. Educational campaigns are needed to alert clinicians and the general public about this increase to help reduce delays in diagnosis, which are so prevalent in young people, but also to encourage healthier eating and more active lifestyles to try to reverse this trend.”
The study also found a narrowing of the gap in colorectal cancer rates between those in their early 50s vs. late 50s. Both colon and rectal cancer incidence rates in adults ages 50 to 54 were half those in adults ages 55 to 59 in the early 1990s, but in 2012 to 2013, they were just 12.4% lower for colon and were equal for rectal cancer.
Signs and symptoms
Siegel says an important message to learn from the study is that young people can and do get colon and rectal cancer, so they should pay attention to signs and symptoms, and so should their doctors.
According to the study, people younger than 55 are 58% more likely to be diagnosed with late-stage disease than older people. The authors say this is “largely due to delayed follow-up of symptoms, sometimes for years, because cancer is typically not on the radar of young adults or their providers.
Siegel says health care providers should educate young patients about healthy lifestyle behaviors, and patients should be aware of colorectal cancer signs and symptoms and report any changes.
The most common signs and symptoms include:
- A change in bowel habits, such as diarrhea, constipation, or narrowing of the stool, that lasts for more than a few days
- A feeling that you need to have a bowel movement that is not relieved by doing so
- Rectal bleeding
- Dark stools, or blood in the stool
- Cramping or abdominal (belly) pain
- Weakness and fatigue
- Unintended weight loss
Because of growing evidence that colorectal cancer is increasing in people younger than age 55, the study authors propose that screening be considered before age 50.
Currently, the American Cancer Society recommends testing starting at age 50 for most people, with screening starting at a younger age for those with a family history of colon or rectal cancer.
Brawley says the risk of colorectal cancer is increasing for every generation born since the 1950s, likely due to the complex relationship between colorectal cancer and obesity, an unhealthy diet, and lack of physical activity.
You can lower your risk by:
- Eating lots of vegetables, fruits, and whole grains and less red meat (beef, pork, or lamb) and processed meats (hot dogs and some luncheon meats).
- Getting regular exercise.
- Watching your weight.
- Avoiding tobacco.
- Limiting alcohol. The American Cancer Society recommends no more than 2 drinks a day for men and 1 drink a day for women.