from 7.9 to 12.9 cases in 2015 per 100,000 people. The reason for the increase isn’t well understood.
The findings were highlighted in a recent review article published online in the New England Journal of Medicine. “It’s a national phenomenon and it’s also occurring in other parts of the developed world. We’re used to seeing mostly older people who have this diagnosis. Now we’re seeing a lot of younger people with this disease. It’s rather alarming,” said author Frank Sinicrope, MD, a medical oncologist with Mayo Clinic, Rochester, Minn.
The trend contrasts with a decline in later-onset CRC likely attributable to increases in screening. As a result of the two trends, but especially the increased number of early-onset cases, the median age of diagnosis dropped from 72 in the early 2000s to 66 today.
“Although patients with early-onset colorectal cancer are more likely to have a hereditary syndrome than those who have later-onset disease, most cases are sporadic, with no identifiable cause. Furthermore, somatic mutational profiling of early-onset colorectal cancers has not revealed previously unidentified or actionable alterations to inform our understanding of the pathogenesis of these cancers or to guide treatment,” he wrote in the review.
“Early-onset colorectal cancers are most commonly detected in the rectum, followed by the distal colon; more than 70% of early-onset colorectal cancers are in the left colon at presentation,” he wrote in the review. Younger patients tend to be unfamiliar with CRC symptoms, which are often mistaken for benign conditions.
“We’ve moved the screening age down to 45, but that still is not going to capture a lot of these patients,” Dr. Sinicrope said. He estimates that 25% of rectal cancers and 10%-12% of colon cancers diagnosed in the next 10 years will be early onset.
Although the direct cause of the increased incidence isn’t clear, Dr. Sinicrope suggested it may reflect changing dietary habits and rising obesity among adolescents. “The sugar-containing beverages, the processed sugar and a lot of red meat in the diet and refined grains … reflect changes in the diet over the last 50 years. We may now be seeing the end result of many of these dietary changes that have occurred,” he said, calling for a greater emphasis on plant-based diets, which promote a healthier gut microbiome that may reduce CRC risk. Western-style diets can change the gut microbiome leading to inflammation which increases the risk of CRC.
Most patients with early CRC present with advanced disease in the left colon. And, pathogenic germline variants are present in one in six patients – half of which are associated with Lynch syndrome which increases the risk for CRC.
Dr. Sinicrope highlighted the need for more risk-based intervention, which in turn requires a better knowledge of family history.
“We need to do better job to risk stratify, and that will help us figure out who’s best to target our screening efforts toward,” Dr. Sinicrope said. He pointed out guidelines from the U.S. Multi-Society Task Force on Colorectal Cancer and the American Cancer Society that can help physicians identify patients who might benefit from earlier screening. The American Cancer Society recommends that CRC screening be conducted at 45 years for average-risk individuals.
“The best screening test is the one that the patient will do,” Dr. Sinicrope said.