By 2030, nearly 10 percent of colon cancers and nearly 25 percent of rectal cancers will be diagnosed in patients younger than the traditional screening age. This growing public health problem is underscored by data trends among 20- to 34-year-olds in the U.S., among whom the incidence of colon and rectal cancer (CRC) is expected to increase by 90% and 124.2%, respectively, by 2030.

Nearly 137,000 people will be diagnosed with
colon and rectal cancer
in the U.S. this year, and more than 50,000 will die of the disease.
colon and rectal cancer
is the third most common cancer among men and women, and the third leading cause of cancer death.

The retrospective cohort study analyzed Surveillance, Epidemiology, and End Results (SEER) data on more than 393,000 patients with histologically confirmed CRC between 1975 and 2010, examining age at diagnosis in 15-year intervals starting at age 20.

The findings build on prior studies of
colon and rectal cancer
trends but go a step further by providing quantitative estimates of exponentially increasing risk for
colon and rectal cancer
among patients who fall under 50, the age at which
colon and rectal cancer
screening becomes recommended for the general public.

The authors point to lifestyle and behavioral factors such as obesity, lack of physical activity and a Western diet as major risk factors for  colon and rectal cancer, though the exact causes of the predicted increases are not known.

"This is an important moment in cancer prevention," said principal investigator George J. Chang, MD, MS, associate professor, Departments of Surgical Oncology and Health Services Research. "We're observing the potential real impact of CRC among young people if no changes are made in public education and prevention efforts. This is the moment to reverse this alarming trend." 

Researchers observed that the annual incidence rate for CRC diagnosed in patients under age 34 is increasing across all stages of disease: localized (confined to the colon or rectum), regional (contiguous and adjacent organ spread, such as to the lymph nodes, kidney and pelvic wall) and distant (referring to remote metastases). The trends indicate that:

• By 2020 and 2030, the incidence rate of colon cancer will increase by 37.8% and 90%, respectively, for patients 20-34. By 2030, this represents a 131.1% incidence rate change of colon cancer in younger patients compared to patients older than 50 years of age.

• Similarly, by 2020 and 2030, the incidence rates for rectosigmoid and rectal cancers are expected to increase by 49.7% and 124.2%, respectively, for the same age group – a 165% incidence rate change compared to patients older than 50 years for these cancers by 2030.

• Among patients 35-49, incidence rates are anticipated to increase 27.7% for colon cancer and 46% for rectal cancer in the same timeframe.

An opposite trend was observed in older patients largely thanks to screening and prevention efforts. There has been a steady decline in the incidence rate of CRC in patients 50 and older, with the most notable declines in regional and distant disease. Based on the predictive model, the researchers anticipate this trend will continue, with incidence declining by 21.2% and 37.8% in 2020 and 2030 for colon, respectively; and 19.0% and 34.3% in 2020 and 2030 for rectum, respectively. The largest decrease is expected for patients older than 75 years.

Lack of screening and risk factors such as obesity and physical inactivity are known contributors to CRC. The authors encourage reduced consumption of processed and fast food and more vegetables and fruits to reduce risk. While the researchers note that the findings do not suggest revisiting screening guidelines at this time, Christina E. Bailey, M.D., MSCI, surgical oncology fellow and the study's first author, added that physicians should be on the lookout for CRC symptoms that might otherwise be dismissed in younger people and only identified as cancer after the disease has progressed.

"While our study observations are limited to CRC, similar concerns are being raised about breast cancer, as we see incidence increasing among younger women," said Chang. "Identifying these patterns is a crucial first step toward initiating important shifts in cancer prevention."