Validation of Advanced Colorectal Neoplasm Risk Categories in a Prospective Cohort in Mexico

Worldwide, there are 1,361,000 new cases of colorectal cancers (CRC) annually, with 694,000 deaths. However, the incidence varies by up to a factor of 10x between high and low incidence countries (eg. USA vs Mexico, incidence rate of 42.54 vs 7.44 / 100,000 inhabitants). Mexico is considered a low-incidence country, with 8,651 new cases and 4,694 deaths annually.CRC is a preventable and detectable disease. Screening programs established in high-incidence countries have managed to reduce the incidence and mortality from this disease and it is considered a cost-effective strategy. In less developed countries where there are no screening programs for CRC, the highest number of deaths occurs despite having the lowest number of cases. It is recognized that a barrier to establishing a screening program in a country with low incidence and limited resources is cost-effectiveness.The prevalence of Advanced Colorectal Neoplasia (ACN) detected by screening colonoscopy in a Mexican cohort of 1172 INNSZ patients was 2.9%. In the US the prevalence is 7.6%. The number of colonoscopies to be performed to detect ACN was estimated at 34 for Mexico and 13 for the US, which suggests that the cost-effectiveness of screening colonoscopy could be 3 times lower in our country.In Mexico there is no national screening program for CRC. The eligible population (adults between 50 and 75 years old) for CRC screening is estimated in 20 million of Mexicans. It is recognized that Mexico does not have enough financial resources nor the infrastructure to screen the entire eligible population either by direct colonoscopy, or by FIT (fecal immunochemical test) followed by colonoscopy. With a 5% frequency of positive FIT, nearly 1,000,000 follow-up colonoscopies would be required annually in a population screening program.An alternative could be to offer screening based on risk, which means only offering screening to the highest-risk population.There are calculators to predict the risk of identifying ACN in a screening colonoscopy, however, none have been developed and validated in the Mexican population. The weight of the risk factors associated with ACN in the Mexican population could be different, so it is necessary to develop and validate an ACN risk calculator that allows the Mexican population to be stratified and to concentrate screening efforts on the population at highest risk.

Inclusion Criteria:Asymptomatic subjects between 50 and 75 years of age-eligible for CRC screening with or without registry at the institute.Note: concerning symptoms of CRC diagnosis will not be admitted: fresh blood in the stool, black stools, unexplained weight loss (>10% of usual body weight). Concerning symptoms of Functional Gastrointestinal Disorder (FGID) will be permitted: loss of appetite, diarrhea, constipation, abdominal pain or discomfort.Subjects who give their informed consent.Subjects who have completed the vaccination schedule against the SARS CoV-2 virus with any of the vaccines approved in Mexico, at least 4 weeks before the colonoscopy.Exclusion Criteria:Personal history of any type of cancer, except basal cell carcinoma or cervical cancer in situ.Personal history of colon polyps.Personal history of abdominal or pelvic radiation due to previous cancer.Relatives with familial adenomatous polyposis (FAP) or hereditary non-polyposis CRC.Inflammatory bowel disease (IBD).High anesthetic risk (ASA greater than 3 of the classification of the American Society of Anesthesiology).Any medical condition that limits life expectancy at the discretion of the investigator.Charlson index > 4.Presence of anemia in the last year according to the WHO definition: women <12 g/dl, men <13 g/dl.Previous colectomy.Colonoscopy in the previous 5 years.Sigmoidoscopy in the previous 3 years.A fecal occult blood test in the past year.CT colonography in the previous 10 years.Clinical data suggestive of CRC such as hematochezia, melena, weight loss greater than 10% of usual body weight in a 6 months period.