The incidence of colorectal cancer continues to decline for older Americans, but researchers have noticed a significant uptick in prevalence among young adults.
The incidence of colorectal cancer (CRC) continues to decline for older Americans, but researchers have noticed a significant uptick in prevalence among young adults. In one of the most striking findings, the age-specific risk of CRC for the youngest cohort is now as high as it was among those born a century earlier, circa 1890.
Using CRC incidence data from 1974 to 2013, researchers created birth cohort models to illustrate age-specific incidence and risk. The study, published in the Journal of the National Cancer Institute (JNCI), was the first since 1994 to assess CRC trends by time period and birth cohort.
Their findings pointed to improvements in older age groups but troubling patterns among young adults. For example, beginning in the mid-1980s, rates of colon cancer declined among those aged 55 or older, but increased by 1.0% per year in adults aged 30 to 39 years and by 2.4% for adults aged 20 to 29 years. The surge in rectal cancer incidence was even sharper, as it decreased by 2% per year for those aged 75 and older but increased by 4% annually for people in their 20s. The age-adjusted proportion of incident cases for those aged 55 and younger doubled from 14.6% in 1989-1990 to 29.2% in 2012-2013.
One of the most alarming findings was related to age-specific trends. The cohort born circa 1890 had double the age-specific risk of colon cancer and triple the risk of rectal cancer, compared with those born in 1950. These risks declined in the first half of the 20th century, then began to rise until the age-specific risk for the youngest cohort born circa 1990 was equivalent to that of the 1890 birth cohort.
These findings take on further urgency when considering the complexity of CRC and the scarcity of treatment options that successfully increase survival. At the annual meeting of the National Comprehensive Cancer Network, oncologist Alan P. Venook, MD, explained that while there have been improvements in CRC diagnosis, “a sum of all treatments that have been developed over the last decade finds that 10 months OS [overall survival] seems the most that has been achieved.”
The authors of the JNCI study noted that while overall screening and detection rates have increased over time, these trends likely do not account for the age-related trends as younger people are still less likely to be screened. Additionally, incidences of both early-stage and advanced-stage cancers have risen at about the same rate, indicating that screening was not a significant factor.
Instead, the researchers wrote, lifestyle changes are a likely culprit for the spike in CRC among young adults. Younger generations have lower levels of smoking and alcohol consumption, but are more likely to have excess body fat driven by unhealthy diets and sedentary lifestyles, which are known risk factors for the disease.
Additionally, younger adults are more likely to be uninsured and less likely to bring up cancer as a concern with their providers. Therefore, increased education about the risks of CRC for both patients and clinicians, along with expanded access to care and screening, could help reverse these trends among young people. The researchers also suggested evaluating the possibility of revising guidelines to recommend an earlier starting point for screening practices, such as age 45 years instead of 50.
“These results highlight the need for etiologic research to elucidate causes for the underlying increase in disease risk in young birth cohorts, as well as creative new strategies to curb the obesity epidemic and shift Americans toward healthier eating and more active lifestyles,” the study authors concluded. “Beyond awaiting scientific discovery and the widespread adoption of healthier living, meaningful action can be taken to mitigate premature morbidity and mortality from this disease through educational campaigns about the importance of timely follow-up of CRC symptoms, regardless of patient age, and age-appropriate screening.”