Table 2.
Randomized Placebo-controlled Trials of Aspirin
| Study | Years conducted | Site | Participants | Study information | Results | Conclusions | References |
|---|---|---|---|---|---|---|---|
| CRC endpoint | |||||||
| British Doctors Aspirin Trial | 1978–1984 | United Kingdom | 5139 Male physicians, born on or after 1900 |
500 mg daily; no placebo; median treatment 6 years | significant decrease in CRC incidence with aspirin use (hazard ratio, 0.70) | decreases CRC incidence | 38 |
| UK-TIA Aspirin Trial | 1979–1986 | United Kingdom and Ireland | 2449 Older than 40 years, recent transient ischemic attack or minor ischemic stroke |
300 mg or 1200 mg daily, median treatment 4.4 years | no significant decrease in CRC incidence with aspirin use (hazard ratio, 0.82) | no decrease in CRC incidence | 38 |
| Physicians’ Health Study | 1982–1988 | US | 22071 male physicians 40–84 years old |
325 mg every other day, study terminated after mean follow-up of 5 years | after early study termination after 5 years due to a significant decrease in cardiovascular events seen in aspirin group, there was no significant reduction in CRC risk with aspirin use (relative risk, 1.15); in post-trial period, after 12 years of additional follow up, aspirin users still had no significantly decreased CRC risk (hazard ratio 1.03) | no decrease in CRC incidence | 41, 42 |
| SALT | 1984–1990 | Sweden | 1360 Recent transient ischemic attack |
75 mg daily, median treatment 2.7 years | no significant decrease in CRC incidence with aspirin use (odds ratio, 0.71) | no decrease in CRC incidence | 39 |
| Thrombosis Prevention Trial | 1989–1997 | United Kingdom | 5085 Men, ages 45–69 years old, at increased risk of vascular events |
75 mg daily, median treatment 6.9 years | significant decrease in CRC incidence with aspirin use (odds ratio, 0.61) | decreases CRC incidence | 39 |
| Women’s Health Study | 1992–2004 | US | 39876 Women health care professionals, 45 years or older |
100 mg every other day | during the trial there was no reduction in CRC risk with aspirin use (relative risk, 0.97); in post-trial period, after 8 additional years of follow up there was a significant decrease in CRC risk in aspirin users (hazard ratio, 0.58), producing overall risk reduction (hazard ratio, 0.80) | decreases CRC incidence | 36, 37 |
| CAPP2 | 1999–2007 | multiple | 861 Lynch syndrome, 25 years or older |
600 mg daily, median follow-up period, 29 months | initial post-trial analysis showed no reduced CRC risk with aspirin use (relative risk, 1.0); longer follow up of participants using aspirin for at least 2 years found reduced risk (hazard ratio, 0.41) | decreases CRC incidence | 55, 56 |
| ASPREE | 2010–2017 | US and Australia | 19114 70 years or older (65 years or older for blacks and Hispanics) |
100 mg daily, median follow up 4.7 years | participants using aspirin had an increased risk of developing colorectal cancer (hazard ratio, 1.77) | increases CRC incidence | 43 |
| Adenoma endpoint | |||||||
| CALGB | 1993–2000 | US | 517 30–80 years old, history of CRC who recently underwent curative resection |
325 mg daily, median time until colonoscopy exam is 12.8 months | aspirin reduced risk of adenoma (relative risk 0.65) and a longer time until an adenoma was detected (relative risk, 0.64), | decreases adenoma risk | 49 |
| CAPP1 | 1993–2003 | Europe | 133 10–21 years old, FAP with no prior colectomy |
600 mg twice daily, colonoscopy after 1 year and then annually | aspirin did not significantly reduce polyp count in the rectum and sigmoid (relative risk, 0.77); treatment for aspirin for more than 1 year significantly decreased the largest polyp size from 6mm to 3mm | does not decrease adenoma formation in FAP | 56 |
| Aspirin/Folate Polyp Prevention Study | 1994–2001 | US and Canada | 1121 21–80 years old with a history of a prior colonic adenoma |
81 mg or 325 mg daily, colonoscopy after approximately 3 years | after at least 1 year, 81 mg associated with lower risk of any adenoma (relative risk, 0.81), and advanced adenoma (relative risk, 0.59),; 325 mg of aspirin was not associated with reduced risk of adenoma | low-dose, but not high-dose aspirin, decreases risk of adenoma recurrence | 44 |
| APACC | 1996–2001 | France | 238 (1 year), 185 (4 years) 18–75 years old with a history of a prior colonic adenoma |
160 mg or 300 mg daily, colonoscopy after 1 and 4 years | after 1 year, aspirin users had decreased risk of having 3 or more adenomas (relative risk, 0.30) and at least 1 adenoma greater than 5mm (relative risk, 0.44); there was no significant differences in adenoma recurrence after 4 years | decreases adenoma risk after 1 year, but not 4 years | 45, 46 |
| UKCAP Trial | 1997–2005 | United Kingdom and Denmark | 853 younger than 75 years old with a history of a prior colonic adenoma |
300 mg daily, colonoscopy after approximately 3 years |
aspirin use was associated with a significantly decreased risk of a recurrent adenoma (relative risk, 0.79) and advanced adenoma (relative risk, 0.63) | decreases adenoma risk | 50 |
| Japan Colorectal Aspirin Polyps Prevention (J-CAPP) | 2007–2009 | Japan | 311 40–60 years old, prior endoscopically removed colonic adenoma or adenocarcinoma |
100 mg daily, colonoscopy after 2 years | aspirin use reduced risk of adenoma and CRC (odds ratio, 0.60), and produced lower risk in nonsmokers (odds ratio, 0.37); no reduced risk of adenoma or CRC in smokers taking aspirin | decreases adenoma and CRC risk, especially in nonsmokers | 47 |