MONDAY, March 11, 2019 (HealthDay News) — Onset of colorectal cancer (CRC) in adults younger than 50 years is distinct from onset in patients aged 50 years or older, according to a study published online March 11 in Cancer.

Alexandra N. Willauer, from the University of Texas MD Anderson Cancer Center in Houston, and colleagues examined clinical and molecular features that differentiate early-onset CRC with that seen in patients aged 50 years or older. Data were included for more than 36,000 patients with CRC.

The researchers found that compared with patients aged 50 years or older, early-onset patients were more likely to have microsatellite instability, synchronous metastatic disease, primary tumors in the distal colon or rectum, and fewer BRAF V600 mutations. Compared with other patients younger than 50 years, those aged 18 to 29 years had fewer adenomatous polyposis coli (APC) mutations and an increased prevalence of signet ring histology (odds ratios, 0.56 and 4.89, respectively). Consensus molecular subtype 1 (CMS1) was the most common subtype in patients aged younger than 40 years; CMS3 and CMS4 were uncommon. CMS2 was relatively stable across ages. The odds of mucinous or signet ring histology were increased, and odds of APC mutations were decreased in early-onset patients with inflammatory bowel disease (odds ratios, 5.54 and 0.24, respectively).

“These notable differences in very young patients with CRC and those with predisposing conditions highlight that early-onset CRC has unique subsets within the population of patients younger than 50 years,” the authors write.

One author disclosed financial ties to the pharmaceutical industry.

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