Daily Aspirin Use and Cancer Mortality in a Large US Cohort

Eric J. Jacobs; Christina C. Newton; Susan M. Gapstur; Michael J. Thun

Disclosures

J Natl Cancer Inst. 2012;104(16):1208-1217. 

In This Article

Abstract and Introduction

Abstract

Background A recent pooled analysis of randomized trials of daily aspirin for prevention of vascular events found a substantial reduction (relative risk [RR] = 0.63, 95% confidence interval [CI] = 0.49 to 0.82) in overall cancer mortality during follow-up occurring after 5 years on aspirin. However, the magnitude of the effect of daily aspirin use, particularly long-term use, on cancer mortality is uncertain.
Methods We examined the association between daily aspirin use and overall cancer mortality among 100 139 men and women with no history of cancer in the Cancer Prevention Study II Nutrition Cohort. Cox proportional hazards regression models were used to estimate multivariable-adjusted relative risks (RRs) and 95% confidence intervals (CIs).
Results Between 1997 and 2008, 5138 participants died from cancer. Compared with no use, daily aspirin use at baseline was associated with slightly lower cancer mortality, regardless of duration of daily use (for <5 years of use, RR = 0.92, 95% CI = 0.85 to 1.01; for ≥5 years of use, RR = 0.92, 95% CI = 0.83 to 1.02). Associations were slightly stronger in analyses that used updated aspirin information from periodic follow-up questionnaires and included 3373 cancer deaths (for <5 years of use, RR = 0.84, 95% CI = 0.76 to 0.94; for ≥5 years of use, RR = 0.84, 95% CI = 0.75 to 0.95).
Conclusion These results are consistent with an association between recent daily aspirin use and modestly lower cancer mortality but suggest that any reduction in cancer mortality may be smaller than that observed with long-term aspirin use in the pooled trial analysis.

Introduction

A recent pooled analysis of randomized trials of daily aspirin for prevention of vascular events by Rothwell et al.[1] reported a statistically significant 15% reduction in overall cancer mortality during an intervention period of up to 10 years. The overall reduction in cancer mortality was mostly attributable to an estimated 37% reduction in cancer mortality during follow-up occurring after 5 years on aspirin (relative risk [RR] = 0.63, 95% confidence interval [CI] = 0.49 to 0.82; 92 cancer deaths in the aspirin group compared with 142 in the control group). Similar effects were observed for lower doses, mostly 75–100mg/day, and higher doses (≥300mg/day).

In contrast to the pooled analysis of trials of daily aspirin,[1] two very large randomized trials of alternate-day aspirin observed no effect on overall cancer mortality,[2,3] raising questions about the frequency of aspirin use needed to reduce cancer risk. The Physicians' Health Study tested 325mg of aspirin every other day for 5 years and reported a relative risk of 1.16 (95% CI = 0.84 to 1.61, 79 cancer deaths on aspirin compared with 68 on placebo).[2] The Women's Health Study tested a lower dose (100mg every other day) for 10 years and reported a relative risk of 0.95 (95% CI = 0.81 to 1.11, 284 cancer deaths on aspirin compared with 299 on placebo).[3] Three large observational studies of aspirin use and cancer mortality reported mixed results,[4–6] although none of these studies examined aspirin use that was both long term and daily.

Results from the pooled trial analysis[1] potentially have very important implications. If these results are accurate and generalizable, people who begin a long-term regimen of daily low-dose aspirin and continue use for 5 years could reduce their subsequent risk of dying from cancer by more than a third. However, uncertainty remains about the magnitude of the effect of daily aspirin use, particularly long-term use, on cancer mortality. In the pooled trial analysis,[1] the relative risk estimate for cancer mortality occurring during follow-up after the first 5 years was based on limited numbers and therefore included a relatively wide confidence interval. In addition, the magnitude of the association with overall cancer mortality is larger than might have been expected, given the absence of apparent effects on cancer mortality in large trials of aspirin taken every other day[2,3] and results from observational studies suggesting that aspirin use does not strongly reduce risk of cancers other than colorectal, esophageal, and stomach cancers.[7]

The purpose of this analysis was to quantify the association between daily aspirin use, particularly long-term use, and overall cancer mortality in the Cancer Prevention Study II (CPS-II) Nutrition Cohort, making use of detailed information on aspirin use collected at multiple time points. Because of the notable 37% reduction in cancer mortality observed in the pooled trial analysis during follow-up occurring after 5 years on daily aspirin,[1] we were particularly interested in cancer mortality among individuals in our cohort with a comparable history of aspirin exposure, that is, current daily aspirin users who had used aspirin during the preceding 5 years (referred to as current daily users of ≥5 years).

Comments

3090D553-9492-4563-8681-AD288FA52ACE
Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.
Post as:

processing....