The incidence of colorectal cancer in adults younger than 50 years of age has increased in the US since 1970. A new study published early online in CANCER, a peer-reviewed journal of the American Cancer Society, found that the proportion of adults diagnosed with colorectal cancer under age 50 in the US has continued to increase over the past decade, and younger adults are diagnosed with more advanced disease.
To determine recent trends in colorectal cancer rates, Dr Boone Goodgame of The University of Texas at Austin, and his colleagues examined information from the National Cancer Database registry, which includes more than 70 percent of new cancer cases in the US. From 2004 to 2015 (the most recent year included in the database), 130,165 patients under age 50 and 1,055,598 patients over age 50 were diagnosed with colorectal cancer.
Among the major findings:
- The proportion of patients diagnosed with colorectal cancer under the age of 50 rose from 10 percent in 2004 to 12.2 percent in 2015.
- The proportion of young onset disease was higher in African American and Hispanic populations than non-Hispanic whites throughout 2004 to 2015.
- 51.6 percent of younger adults were diagnosed with more advanced stages of cancer (stage III/IV) versus 40 percent in those older than 50 years.
- Diagnoses in men under the age of 50 years rose only in non-Hispanic whites, while in women, Hispanic and non-Hispanic whites had an increase in younger diagnoses over time.
- Rates of colorectal cancer diagnosis in young adults increased over time regardless of income level. The highest proportion of young adult diagnoses occurred in the top income category.
- The proportion of colorectal cancers diagnosed in younger individuals rose in urban areas, but not in rural areas.
"Several studies have shown that the rates of colorectal cancer in younger adults have risen slowly in the US since the 1970s, but for practicing physicians, it feels like we are seeing more and more young people with colorectal cancer now than we were even 10 years ago," said Goodgame. "Until just last year, guidelines recommended colon cancer screening beginning at 50. Now many guidelines do recommend screening at age 45, but most physicians and patients don't appear to be following those recommendations."
The researchers noted that the cause of increasing rates of colorectal cancer in younger patients is unclear, but emerging research suggests that it may be a combination of increases in body weight and changes in gastrointestinal bacteria.
In an accompanying editorial, Dr Chyke Doubeni of the University of Pennsylvania, pointed to the need for additional research: "Because the number of colorectal cancer cases from inherited causes are much higher in younger individuals, it is unknown whether screening for sporadic cases in a group with such low disease rate can result in a favourable balance of harms and benefits. It is therefore imperative that the various hypotheses for increasing colorectal cancer incidence among people younger than 50 be rigorously tested to determine if changing the current screening age in people who are not at increased familial risk represents the most appropriate public health response."
The American Cancer Society's guideline for colorectal cancer screening recommends that average-risk adults aged 45 years and older undergo regular screening, either with colonoscopy or with alternatives such as faecal immunochemical tests and faecal occult blood tests.