A new study finds that both colon and rectal cancers are rising among young US adults, even as the rates fall among older adults.
When taking age 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 colorectal cancer risk was lowest. The study was published in the Journal of the National Cancer Institute.
Three in ten rectal cancer diagnoses are now in patients younger than age 55.
Overall, colorectal cancer rates have been declining in the United States since the mid-1980s, with screenings leading to the largest drops in the most recent decade. Recent studies have reported increasing colorectal cancer incidence in adults under 50, for whom screening is not recommended for those at average risk.
In this study, researchers used a modeling technique to separate factors that influence all ages, such as changes in medical practice, from those that vary by generation, typically due to changes in behavior. They reviewed incidence trends from 1974 through 2013 in nine Surveillance, Epidemiology, and End Results (SEER) program registries among all patients 20 years and older diagnosed with colorectal cancer. There were 490,305 cases included, which were analyzed by five-year-age groups.
The study found that after decreasing since 1974, colon cancer incidence rates increased by 1% to 2% per year from the mid-1980s through 2013 in adults ages 20 to 39. In adults 40 to 54, rates increased by a half to 1 percent 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 those in their 20s and from 1980 to 2013 in those in their 30s. In adults ages 40 to 54, rectal cancer rates increased by 2% per year from the 1990s to 2013. In contrast, rectal cancer rates in adults age 55 and older have generally been declining for at least 40 years, well before widespread screening.
The authors write that given these findings, screening before age 50 should be considered.
For lowering colorectal cancer risk through lifestyle, AICR research shows there several steps individuals can do. Daily exercise, staying a healthy weight, drinking alcohol moderately (if at all) and cutting processed meat are among the lifestyle factors that link to reduced risk of these cancers.
The JNCI study was funded by the Intramural Research Department of the American Cancer Society and the Intramural Research program of the National Institutes of Health/National Cancer Institute.
Source: Colorectal cancer incidence patterns in the United States, 1974-2013; J Natl Cancer Inst (2017) 109(8).
Published on March 7, 2017