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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.
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.
Numbers are from the trial as recorded here; see the source links in the table below. This is orientation, not medical advice: ask your team how closely the trial population matches you.
861 randomised.
40 cases · 58 cases
Source509 participants across both arms completed 2 years
Source95% CI 0.39 to 0.87, p 0.0085
Source| Endpoint | Arm | n | Value | HR (95% CI) | p | Source |
|---|---|---|---|---|---|---|
| Colorectal cancer over a mean of 10 years of follow-up (intention to treat)primary | Aspirin 600 mg daily | 427 | 9% | 0.65 (0.43 to 0.97) | 0.035 | link |
| Placebo | 434 | 13% | ||||
| Colorectal cancer, per protocol (at least 2 years of treatment) | Aspirin 600 mg daily | - | 509 participants across both arms completed 2 years | 0.56 (0.34 to 0.91) | 0.019 | link |
| Placebo | - | - | ||||
| Incidence rate ratio for colorectal cancer accounting for multiple primaries (intention to treat) | Aspirin 600 mg daily | - | 0.58 | - | - | link |
| Placebo | - | 1 |
Shares CAPP2: two years of aspirin cuts bowel cancer in Lynch syndrome by more than a third over 10 years, Aspirin for cancer prevention and adjuvant therapy, Mismatch-repair deficient (MSI-high) colorectal cancer.
Shares Aspirin, Mismatch-repair deficient (MSI-high) colorectal cancer.
Shares Aspirin, Mismatch-repair deficient (MSI-high) colorectal cancer.
Shares Aspirin, Aspirin for cancer prevention and adjuvant therapy.
Shares Aspirin, Aspirin for cancer prevention and adjuvant therapy.
Shares CAPP2: two years of aspirin cuts bowel cancer in Lynch syndrome by more than a third over 10 years, Aspirin for cancer prevention and adjuvant therapy.
Shares John Burn, CAPP2: two years of aspirin cuts bowel cancer in Lynch syndrome by more than a third over 10 years, Aspirin for cancer prevention and adjuvant therapy, Mismatch-repair deficient (MSI-high) colorectal cancer.
Shares Aspirin, Aspirin for cancer prevention and adjuvant therapy.