# CAPP2

Source: https://onco.cc/trials/capp2/  
OnCo record `capp2` (Trial). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

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.

Over 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.

## Fields

- Kind: Trial
- Status: positive
- Last checked: 2026-09-22
- Also known as: CAPP 2; Colorectal Adenoma/Carcinoma Prevention Programme 2
- Tags: soc-trials
- Registry id: 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)
- Enrolled: 861
- 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.
- Outcomes: Colorectal cancer over a mean of 10 years of follow-up (intention to treat): Aspirin 600 mg daily 9% vs Placebo 13%, HR 0.65; Colorectal cancer, per protocol (at least 2 years of treatment): Aspirin 600 mg daily vs Placebo, HR 0.56; Incidence rate ratio for colorectal cancer accounting for multiple primaries (intention to treat): Aspirin 600 mg daily 0.58 vs Placebo 1

## Sources

- ISRCTN59521990: https://www.isrctn.com/ISRCTN59521990

## Connected records

- cancers: [Mismatch-repair deficient (MSI-high) colorectal cancer](https://onco.cc/cancers/msi-high-colorectal/)
- technologies: [Aspirin for cancer prevention and adjuvant therapy](https://onco.cc/technologies/aspirin-cancer-prevention/)
- drugs: [Aspirin](https://onco.cc/drugs/aspirin/)
- key papers: [CAPP2: cancer prevention with aspirin in Lynch syndrome, 10-year follow-up and registry-based 20-year data](https://onco.cc/key-papers/paper-capp2-aspirin-lynch-syndrome-10-year-burn-lancet-2020/)

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