Description of the Evidence
Cardiovascular Risks Associated With Celecoxib and Rofecoxib Dose/Drugs continued...
Four reports in 2007, 2010, 2011, and 2012 [57,62,63,64] have analyzed long-term follow-up of RCTs of daily ASA versus the control. The 2007 analysis reported on two RCTs with reliable follow-up of more than 20 years. This report found that the use of 300 mg or more of ASA per day for at least 5 years reduced the incidence of CRC after a latency of 10 years (RR at 10–19 years [0.60; 95% CI, 0.42-0.87]). The 2010 analysis analyzed long-term follow-up data from four RCTs, finding that allocation to ASA for 5 or more years reduced the 20-year incidence and mortality of proximal colon cancer (adjusted incidence HR = 0.35; 95% CI, 0.20–0.63; adjusted mortality HR = 0.24; 95% CI, 0.11–0.52) and also reduced the 20-year risk of rectal cancer (RR = 0.58; 95% CI, 0.36–0.92) but not distal colon cancer. There was no increase in benefit at doses more than 75 mg/day. The absolute 20-year risk reduction in fatal CRC was 1.76% (95% CI, 0.61–2.91).
The 2011 analysis examined data from eight RCTs, seven of which provided individual patient data and three of which provided 20-year follow-up data. In trials with allocation to ASA of at least 5 years, the 20-year HR for CRC mortality was 0.60 (95% CI, 0.45–0.81). Six RCTs, including five from the United Kingdom, were included in a meta-analysis in which patients were randomly assigned to receive either aspirin or placebo and mean scheduled duration of trial treatment was 4 years or more. Individual patient data for all in-trial cancer deaths were obtained. In the three United Kingdom trials, cancer deaths after completion of the trials were obtained via death certification and cancer registration, taking the follow-up to 20 years after randomization. Based on meta-analysis of odds ratios from each trial rather than on more sensitive actuarial analysis of the individual patient data, allocation to aspirin in the RCTs reduced the 20-year risk of death due to colorectal (and esophageal) cancer. Odds ratios for 'maximum aspirin use' were 0.55 for colorectal cancer risk (95% CI, 0.41–0.76) and 0.47 for esophageal cancer risk (95% CI, 0.27–0.81) and for 'any aspirin use' were 0.58 for colorectal cancer risk (95% CI, 0.44–0.78) and 0.51 for esophageal cancer (95% CI, 0.31–0.83).