Are We Getting Closer to Molecular Population Screening for Colorectal Cancer?

Extract

The best methods to bring about a reduction in the incidence and mortality of colorectal cancer in the world have been the subject of much debate in recent years. Colorectal cancer is highly preventable through behavioral changes in diet and physical activity; still, much effort has been invested in developing efficient screening technologies for secondary prevention.

Public health theory stresses a number of requirements that must be met before screening for a disease can be initiated ( 1 ). This line of thought differs from the usual clinical situation in which symptomatic patients present themselves to the health system in search of medical help. The screening setting refers to very large populations that are usually symptom free and at a very low probability of having the disease of interest at any given round of screening. The disease of concern needs to be clinically significant in terms of incidence, prevalence, mortality, or suffering and have a natural history that can be influenced by a timely intervention. Screening technologies need to have proven and substantial efficacy. Specificity takes priority over sensitivity, contrary to the case when diagnosing symptomatic patients. Efficacy is best proven through randomized controlled trials that show disease-specific mortality reduction. Studies that are designed in a nonrandomized manner are prone to major biases, such as length bias, lead-time bias, and selection bias ( 1 ), all of which can seriously diminish the validity of the results in terms of the direction and the magnitude of the effect. The screening technology needs to be as simple as possible, easy to perform, cheap, and, most importantly, acceptable to the population, that is, noninvasive and with an overall balance of more benefit than harm.