Purpose: Use of non-steroidal anti-inflammatory drugs (NSAIDs) may reduce the incidence of several cancers. A recent meta-analysis of randomized trials of aspirin reported a reduction in cancer mortality; however, few studies have investigated whether aspirin or other NSAIDs reduce overall cancer risk.
Methods: 64,847 residents of western Washington State, aged 50-76, completed a baseline questionnaire in 2000-2002 and reported on their use of individual NSAIDs over the past 10 years. Behavior was categorized as non-use, low (<4 days/week or <4 years), and high (≥4 days/week and ≥4 years). Over 7 years of follow-up, 5,946 incident invasive cancer cases were identified. Multivariable proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI).
Results: Relative to non-use, high 10-year use of regular-strength NSAIDs was inversely associated with total cancer risk in men (HR 0.88, 95% CI: 0.79-0.97) and not associated with risk in women (HR 1.10, 95% CI: 0.96-1.25; p interaction <0.01). Use of regular-strength NSAIDs was strongly and inversely associated with colorectal cancer risk in men and women, but differentially associated with sex-specific risk of shared cancer sites other than colorectal cancer (men: HR 0.83, 95% CI: 0.71-0.97; women: HR 1.18, 95% CI: 0.97-1.44; p interaction < 0.01).
Conclusions: Long-term use of NSAIDs was associated with a reduced risk of total cancer among men and colorectal cancer among both sexes. Our findings do not support NSAID use for overall cancer prevention among women. Additional high-quality studies with long-term follow-up for cancer among women are needed before a public health recommendation can be made.