A Trial of Omeprazole and Low Dose Aspirin to Identify Colorectal Biomarkers of Preventive Efficacy

Inclusion Criteria: * Age 18-75 * Individuals who are due for a standard of care colonoscopy. * Have a prior history of colorectal neoplasia including any ONE of the following: * Multiple (\>=5) colorectal adenomas on most recent colonoscopy * Multiple (\>=5) sessile serrated polyps on most recent colonoscopy * Adenomatous polyps meeting criteria for colon polyposis of unknown etiology (\> 20 lifetime adenomas) * Serrated polyps meeting criteria for serrated polyposis syndrome * History of incompletely resected colorectal polyp(s) (adenoma or sessile serrated polyp) on most recent colonoscopy * Willing to avoid taking non-steroidal anti-inflammatory drugs that are not provided by the study in the 30 days prior to Visit 1 and while on study. * Willing to avoid taking proton pump inhibitors that are not provided by the study in the 30 days prior to Visit 1 and while on study. * Women of child-bearing potential must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) for the duration of study participation since endoscopy is not recommended during pregnancy. * Demonstrate adequate organ and marrow function obtained within the last 60 days as defined below: * Absolute neutrophil count ≥1,000/microliter * Platelets ≥100,000/microliter * Total bilirubin ≤ 1.5 fold of the institutional upper limit of normal Note: Higher total bilirubin levels (≤ 3 mg/dL) can be allowed if due to known benign liver condition such as Gilbert…