Importance of screening for early-onset colorectal cancer

RESEARCH into early-onset colorectal cancer (CRC) has found unique subgroups among younger patients and has outlined risk factors and prevalence of additional diseases, such as microsatellite instability. The researchers believe that this study could be used to improve the screening process in detection of this cancer.

There are clinical and genetic distinctions in early-onset CRC and standard CRC. A review of 36,000 patients demonstrated unique subgroups in younger patients with CRC and found that patients with early-onset CRC were more likely than those with standard CRC to have synchronous metastatic disease, microsatellite instability, and distal primary tumours (p=0.0090, p=0.0380, and p<0.0001, respectively); however, they were less likely to have BRAF V600 mutations (p<0.0010).

Dr Scott Kopetz, University of Texas Health Science Center, Houston, Texas, USA said: “Physicians should recognise that the traditional risk factors for colorectal cancer do not appear to apply in early-onset disease.” He also outlined how the biology of these diseases differs and suggested an association between early-onset CRC and worse outcomes. Early-onset CRC is more prevalent in the rectum and descending colon, more common in Hispanic patients, and most highly diagnosed in patients without CRC in their family history.

Within the study, the researchers made distinctions between concerning consensus molecular subtypes (CMS): CMS1 was the most common, CMS2 had stable prevalence across age groups, and CMS3 and CMS4 were uncommon in early-onset CRC. They also found that early-onset patients <30 years of age had higher prevalence of signet ring histology and a lower chance of adenomatous polyposis coli mutations than patients aged 30–49 years of age.

Further study is needed into patients aged 18–29 years and patients displaying a predisposition to medical conditions including inflammatory bowel disease. The researchers said that screening has resulted in a reduction of both CRC incidence and associated mortality in patients >50 years of age. However, prevalence of early-onset CRC has increased 1–3% in those aged <30 years. There is a recommendation for screening to begin at 45 years of age.

Dr Kopetz concluded: “With additional studies, this work can be used to better guide screening efforts. For example, the higher prevalence of the disease in the left side of the colon and rectum could allow screening tests other than colonoscopy that may be less invasive or resource intensive.