{"entity":{"id":"capp2","kind":"trial","name":"CAPP2","aka":["CAPP 2","Colorectal Adenoma/Carcinoma Prevention Programme 2"],"tldr":"CAPP2 followed people with Lynch syndrome, an inherited condition that carries a very high risk of bowel cancer, for ten years after two to four years on aspirin or placebo: those who took aspirin developed about a third fewer bowel cancers, which is why daily aspirin is now offered to people with the syndrome.","summary":"CAPP2 was a double-blind randomised placebo-controlled trial in which 861 carriers of Lynch syndrome from 43 international centres were assigned to 600 mg aspirin daily or placebo, with treatment lasting a mean of 25 months, and cancer outcomes followed for at least ten years (up to 20 years through registries in England, Finland and Wales). The primary endpoint was colorectal cancer.\n\nOver a mean of ten years, 40 of 427 aspirin participants (9 percent) developed colorectal cancer against 58 of 434 on placebo (13 percent), a hazard ratio of 0.65 by intention to treat and 0.56 among those who completed two years of treatment. Non-colorectal Lynch cancers were not significantly reduced and adverse events during treatment did not differ. The trial is the evidence for daily aspirin in Lynch syndrome on the corpus's mismatch-repair-deficient colorectal cancer page, and the CaPP3 dose-finding trial followed it.","status":"positive","asOf":"2026-09-22","links":[{"label":"ISRCTN59521990","url":"https://www.isrctn.com/ISRCTN59521990"}],"tags":["soc-trials"],"related":[],"cancers":["msi-high-colorectal"],"sections":[],"technologies":["aspirin-cancer-prevention"],"targets":[],"drugs":["aspirin"],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":["paper-capp2-aspirin-lynch-syndrome-10-year-burn-lancet-2020"],"journals":[],"dependsOn":[],"notes":[],"nct":"ISRCTN59521990","phase":"3","setting":"People with Lynch syndrome at 43 centres worldwide: 600 mg aspirin daily or placebo for up to four years (a resistant starch factorial arm was reported separately), with colorectal cancer as the primary endpoint over a planned ten years of follow-up","sponsor":"Newcastle University (CAPP2 Investigators)","result":"Colorectal cancer in 9 percent of participants on aspirin against 13 percent on placebo over ten years (hazard ratio 0.65, p 0.035); hazard ratio 0.56 among those who completed two years of treatment.","yearReported":2020,"enrolled":861,"enrolledBasis":"randomised","enrolledNote":"CAPP2 has no ClinicalTrials.gov record; the figure is the 861 participants randomised in the Lancet 2020 report (427 aspirin, 434 placebo) of 937 who started treatment; the trial is registered as ISRCTN59521990.","outcomes":[{"endpoint":"Colorectal cancer over a mean of 10 years of follow-up (intention to treat)","primary":true,"unit":"%","arms":[{"name":"Aspirin 600 mg daily","n":427,"value":9,"note":"40 cases"},{"name":"Placebo","n":434,"value":13,"note":"58 cases"}],"hr":0.65,"ci":[0.43,0.97],"p":"0.035","source":"https://doi.org/10.1016/S0140-6736(20)30366-4"},{"endpoint":"Colorectal cancer, per protocol (at least 2 years of treatment)","unit":"%","arms":[{"name":"Aspirin 600 mg daily","note":"509 participants across both arms completed 2 years"},{"name":"Placebo"}],"hr":0.56,"ci":[0.34,0.91],"p":"0.019","source":"https://doi.org/10.1016/S0140-6736(20)30366-4"},{"endpoint":"Incidence rate ratio for colorectal cancer accounting for multiple primaries (intention to treat)","arms":[{"name":"Aspirin 600 mg daily","value":0.58,"note":"95% CI 0.39 to 0.87, p 0.0085"},{"name":"Placebo","value":1}],"source":"https://doi.org/10.1016/S0140-6736(20)30366-4"}]},"route":"/trials/capp2/","neighbours":{"cancer":[{"id":"msi-high-colorectal","kind":"cancer","name":"Mismatch-repair deficient (MSI-high) colorectal cancer","route":"/cancers/msi-high-colorectal/"}],"technology":[{"id":"aspirin-cancer-prevention","kind":"technology","name":"Aspirin for cancer prevention and adjuvant therapy","route":"/technologies/aspirin-cancer-prevention/"}],"drug":[{"id":"aspirin","kind":"drug","name":"Aspirin","route":"/drugs/aspirin/"}],"paper":[{"id":"paper-capp2-aspirin-lynch-syndrome-10-year-burn-lancet-2020","kind":"paper","name":"CAPP2: cancer prevention with aspirin in Lynch syndrome, 10-year follow-up and registry-based 20-year data","route":"/key-papers/paper-capp2-aspirin-lynch-syndrome-10-year-burn-lancet-2020/"}]}}