Challenges around diagnosis of early onset colorectal cancer, and the case for screening.

Background: Colorectal cancer (CRC) is the third most diagnosed cancer in the world, with an estimated 1.93 million cases diagnosed in 2020. While the overall CRC incidence in many countries is falling there has been a dramatic increase in CRC in those aged under 50 (early onset colorectal cancer, EOCRC). The reason for this increase in EOCRC is unknown. As the best predictor of survival is stage at diagnosis, early diagnosis is likely to be beneficial and population screening may facilitate this.

Methods: A narrative review of the literature was undertaken.

Results: Improving time to diagnosis in symptomatic patients is beneficial. However, by the time symptoms develop, over a third of patients already have metastatic disease. Screening asymptomatic patients (with Faecal Immunochemical test (FIT) and colonoscopy) has been proved to be effective in older patients (>60 years). In younger populations, the decreasing incidence rates of CRC previously made cost effectiveness, compliance and therefore benefit questionable. Now, with the increasing incidence of CRC in those under 50 years of age, modelling suggests screening with FIT and colonoscopy is cost effective from 40 years of age. There is evidence that some countries screening below 50 have prevented the rise in EOCRC incidence. Additionally the use of new and novel non-invasive biomarkers may also be able to improve the accuracy of screening asymptomatic patients.

Conclusion: Diagnosis of EOCRC once symptoms develop is often too late, and screening patients from age 40 is the best way to improve outcomes in this group.