There has been an alarming increase in the rate of colorectal cancer in young patients in the United States, most of whom don’t fall under the current colorectal cancer screening recommendations. In contrast to older patients, cancers in younger patients are more commonly located on the left side of the colon and in the rectum.

Colorectal cancers that are not due to hereditary syndromes are typically caused by genetic mutations or the addition of methyl groups to DNA, which in turn can lead to silencing of tumor suppressor genes. Colon cancers due to such genetic changes tend to be right-sided. Such methylation levels are thought to increase with age.

The authors studied the cancers of 57 patients under 50 years of age with colorectal cancer and compared these to 440 cancers in patients over the age of 50. They found that none of the young patients had “hypermethylated” cancers in contrast to 22% of older patients. Additionally, this percentage increased with increasing age, being 42% in those over 80 years old vs 5% in those aged 51–60 years old. As expected, 81% of cancers in young patients were located in the left side of the colon, in contrast to patients over 50 where more than half of the cancers were on the right side of the colon. Dr. Chouhan sais, “This study has confirmed our impression that genetic changes associated with hypermethylation are uncommon in young patients with colorectal cancer.” These findings may explain the increased finding of left-sided and rectal cancers in this young group of patients.

The authors point out at least two important implications from these results:

1. The changing biology of colorectal cancers by age suggests that research into cancer risk factors and targeted therapy of the tumors themselves can have different targets according to the ages of the patient groups concerned. One size does not fit all.

2. The different locations of cancers according to age means that approaches to endoscopic screening can differ according to the age of the patients. Colonoscopy is increasingly important as you get older while flexible sigmoidoscopy is more appropriate in the young.