Although the incidence of colorectal cancer has decreased in recent years among older adults in the United States, it is on the rise among younger ones, according to a new study from the American Cancer Society (ACS).
From the late 1980s to the early 2000s, the average age of diagnosis was 72, but by 2016 (the year for which the most recent statistics are available), that age had dropped to 66. That means half of all Americans diagnosed each year with colorectal cancer (cancer of the colon or rectum) are aged 66 or younger.
Older people — those aged 65 and up — still make up the majority of cases of colorectal cancer, but new diagnoses are occurring faster among younger adults than among older ones.
The downward shift in age is driven in large part by a dramatic increase in colorectal cancer cases among people under the age of 50.
The report, which was published in CA: A Cancer Journal for Clinicians, also found “striking” racial and ethnic disparities in both the incidence and death rates for colorectal cancer.
“Although overall colorectal cancer incidence and mortality continue to decline, this progress is increasingly confined to older age groups and is marred by vast disparities,” said Rebecca Siegal, the lead author of the report and scientific director of surveillance research at the ACS, in a released statement.
“More timely diagnosis among younger patients remains critical while we await answers to why [colorectal cancer] incidence is rising in young and middle-aged adults,” she added.
Excluding skin cancers, colorectal cancer is the third most common type of cancer diagnosed in both men and women in the United States and the second most common cause of cancer death. This year, about 148,000 Americans will be diagnosed with the disease, and 53,000 will die from it.
About 18,000 of those diagnoses (12 percent) will be among people under the age of 50 — the equivalent of 49 new cases per day. In addition, about 3,600 of those deaths (10 per day) will be in this age group.
Colorectal cancer has been linked to inherited genetic conditions. More than half of all cases are attributable, however, to five modifiable risk factors — smoking, an unhealthy diet, excess weight, physical inactivity and high alcohol consumption — and are thus considered preventable. Appropriate screening, which looks for precancerous signs of the disease as well as for the cancer itself, can also help lower the risk of developing and dying from the disease.
Most health organizations in the U.S. advise people to begin colorectal screening at age 50, although the ACS lowered that age to 45 in its most recent recommendations.
Specific age trends
To compile the new report, Siegal and her colleagues used data collected by various government agencies, including the National Cancer Institute and the Centers for Disease Control and Prevention.
Their analysis of that data revealed difference trends among different age groups.
For people aged 65 and older, the incidence of colorectal cancer fell rapidly during the 2000s, a trend believed to be the result of more widespread early detection and screening. During the most recent years for which data is available — 2011-2016 — the incidence rate for this age group dropped an average of 3.3 percent per year.
For people aged 50 to 64, the incidence rate also declined during the 2000s, but it then increased at an average of 1.0 percent per year between 2011 and 2016.
A sign of the shift: the median age of diagnosis has dropped from age 72 in the early 2000s (or 2001-2002) to 66 during 2015-2016
For people younger than 50, the incidence rate has been increasing since the mid-1990s. It rose rapidly, however — at an average rate of 2.2 percent per year — between 2011 and 2016.
These increases reflect higher risk among generations born since the 1950s — a risk that is carried forward with those generations as they age, say the researchers.
Younger adults are also more likely to be diagnosed with late-stage colorectal cancer. The report found that 26 percent of people aged 50 and younger have late-stage disease when they are diagnosed compared to 19 percent of people aged 65 and older.
Researchers aren’t sure why the incidence of colorectal cancer is rising among younger people. But because the increase has occurred within a relatively short timeframe, they believe the causes are more likely to be environmental — eating an unhealthful diet, not exercising regularly and being overweight — than the result of any genetic changes.
The growing incidence of colorectal cancer among younger adults is being primarily driven by rising rates among non-Hispanic whites, although rates among other groups, particularly Alaska Natives, are also climbing rapidly.
In 2012-2016, the incidence rate for people of all ages was lowest for people with Asian and Pacific Islanders ancestry (30 cases per 100,000 people), followed by whites (38.6 cases per 100,000), blacks (45.7 cases per 100,000) and Alaska Natives (89 per 100,000).
The racial disparities associated with colorectal cancer are even starker when death rates are considered. For example, blacks are 18 percent more likely to develop the disease, but 38 percent more likely to die from it than non-Hispanic whites. And the death rates among Alaskan Natives are double those among blacks.
Some level of those disparities can be found in Minnesota, where blacks are 17 percent more likely than whites to develop colorectal cancer (43.7 vs. 38.1 per 100,000) and almost 10 percent more like die from it.
Poor access to high-quality health care, including screening, is a major cause of these disparities, the researchers note.
“One in three people 50 and older is not up-to-date on screening, [and] many of them have never been screened at all,” said Siegal. “We could save countless lives by increasing access to screening in rural and other low-income areas, especially in Alaska, and incentivizing primary care clinicians to ensure that all patients 45 and older are screened, as well as facilitating healthier lifestyles in our communities.”
FMI: The study can be found and read in full on the website for CA: A Cancer Journal for Clinicians. To learn how to recognize the signs and symptoms of bowel cancer, go to the American Cancer Society website.