Low-Dose Aspirin Use and the Incidence of Colorectal Cancer
Low-Dose Aspirin Use and the Incidence of Colorectal Cancer
Background Considerable evidence suggests that aspirin has a chemopreventive effect on colorectal cancer (CRC). However, optimal dose and treatment duration have not been defined, and data on the effects of low-dose aspirin are contradictory.
Aim To determine if the incidence of CRC in patients with low-dose aspirin use was lower than in those without aspirin use.
Method From Taiwan's National Health Insurance research database, aspirin users (n = 1985) were defined as adults (age ≥20 years) with at least 3.5 years of regular low-dose aspirin use (50–150 mg per day) between 1998 and 2002. Non-users (n = 7940) were those who did not use aspirin and were matched 4:1 with the user group by age, gender, date of ambulatory care (index date), and presence of known risk factors for cardiovascular disease (including hypertension, diabetes mellitus and hyperlipidaemia). Follow-up of the two study groups was made until the end of 2010, and incidences and hazard ratios of colorectal cancer were determined.
Results During a median follow-up period of 8.9 years, 129 non-users and 14 users developed CRC, corresponding to incidence rates of 180.43 and 79.42 per 100 000 person-years respectively. Duration of aspirin use among users ranged from 3.5 to 12.6 years (mean 8.7 years). The multivariate-adjusted hazard ratio for CRC was 0.5 (95% confidence interval 0.28–0.87) among users as compared with non-users.
Conclusions Long-term use of low-dose aspirin appears to be associated with a lower incidence of CRC in patients with high cardiovascular risk. Further randomised clinical trials are necessary to confirm these findings.
The incidence rates of colorectal cancer (CRC) are steadily increasing in East Asia, even though they have decreased or stabilised in Western countries. CRC is the second most commonly diagnosed cancer and the third leading cause of cancer-related death in Taiwan.In addition to promoting population-based screening using faecal occult blood testing (FOBT) combined with colonoscopy or flexible sigmoidoscopy, chemoprevention has been extensively investigated as a means of primary prevention of CRC.
Considerable evidence from clinical trials and epidemiological observational studies of various populations suggests that regular aspirin use reduces CRC risk. However, the efficacy of low-dose aspirin (50–160 mg) remains controversial because of inconsistent findings in clinical trials and observational studies. Earlier observational studies suggested that higher doses (300–325 mg per day) may be required. Two randomised trials – the Women's Health Study and the Physicians' Health Study – failed to demonstrate a protective effect of low-dose aspirin on CRC risk among women or men respectively. However, a meta-analysis of four randomised trials and one case-control study found that 75 mg of aspirin per day may be beneficial. The heterogeneity of results regarding low-dose aspirin use may be partly due to differences among the study populations and methodological issues, including study design and the sample size of specific populations.
No observational study has assessed the role of low-dose aspirin in modifying CRC risk in an Asian population and therefore we conducted a nationwide population-based hybrid study of a cohort with comparison group to investigate association between low-dose aspirin use and subsequent risk of CRC.
Abstract and Introduction
Abstract
Background Considerable evidence suggests that aspirin has a chemopreventive effect on colorectal cancer (CRC). However, optimal dose and treatment duration have not been defined, and data on the effects of low-dose aspirin are contradictory.
Aim To determine if the incidence of CRC in patients with low-dose aspirin use was lower than in those without aspirin use.
Method From Taiwan's National Health Insurance research database, aspirin users (n = 1985) were defined as adults (age ≥20 years) with at least 3.5 years of regular low-dose aspirin use (50–150 mg per day) between 1998 and 2002. Non-users (n = 7940) were those who did not use aspirin and were matched 4:1 with the user group by age, gender, date of ambulatory care (index date), and presence of known risk factors for cardiovascular disease (including hypertension, diabetes mellitus and hyperlipidaemia). Follow-up of the two study groups was made until the end of 2010, and incidences and hazard ratios of colorectal cancer were determined.
Results During a median follow-up period of 8.9 years, 129 non-users and 14 users developed CRC, corresponding to incidence rates of 180.43 and 79.42 per 100 000 person-years respectively. Duration of aspirin use among users ranged from 3.5 to 12.6 years (mean 8.7 years). The multivariate-adjusted hazard ratio for CRC was 0.5 (95% confidence interval 0.28–0.87) among users as compared with non-users.
Conclusions Long-term use of low-dose aspirin appears to be associated with a lower incidence of CRC in patients with high cardiovascular risk. Further randomised clinical trials are necessary to confirm these findings.
Introduction
The incidence rates of colorectal cancer (CRC) are steadily increasing in East Asia, even though they have decreased or stabilised in Western countries. CRC is the second most commonly diagnosed cancer and the third leading cause of cancer-related death in Taiwan.In addition to promoting population-based screening using faecal occult blood testing (FOBT) combined with colonoscopy or flexible sigmoidoscopy, chemoprevention has been extensively investigated as a means of primary prevention of CRC.
Considerable evidence from clinical trials and epidemiological observational studies of various populations suggests that regular aspirin use reduces CRC risk. However, the efficacy of low-dose aspirin (50–160 mg) remains controversial because of inconsistent findings in clinical trials and observational studies. Earlier observational studies suggested that higher doses (300–325 mg per day) may be required. Two randomised trials – the Women's Health Study and the Physicians' Health Study – failed to demonstrate a protective effect of low-dose aspirin on CRC risk among women or men respectively. However, a meta-analysis of four randomised trials and one case-control study found that 75 mg of aspirin per day may be beneficial. The heterogeneity of results regarding low-dose aspirin use may be partly due to differences among the study populations and methodological issues, including study design and the sample size of specific populations.
No observational study has assessed the role of low-dose aspirin in modifying CRC risk in an Asian population and therefore we conducted a nationwide population-based hybrid study of a cohort with comparison group to investigate association between low-dose aspirin use and subsequent risk of CRC.