Aspirin use and the incidence of breast, colon, ovarian, and pancreatic cancers in elderly women in the Iowa Women's Health Study

Few studies have evaluated the chemopreventive effect of aspirin on the cancer risk in elderly women. We examined associations between frequency, dose, and duration of aspirin use with incidence of 719 aspirin-sensitive cancers (cancers of colon, pancreas, breast, and ovaries) in the Iowa Women's Health Study (IWHS), a prospective cohort of women over 70 years old. Aspirin frequency, dose, and duration were self-reported in the 2004 IWHS questionnaire. Women were followed-up to 2011. Cancer cases were ascertained by linkage to the Iowa State Health Registry. Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95 % confidence intervals (CI). Among the 14,386 women, 30 % were nonusers of aspirin; 34 % used low-dose aspirin, and 36 % used regular- or high-dose aspirin. Compared with nonuse of aspirin, the HRs (95 % CI) for incidence of aspirin-sensitive cancers were 0.87 (0.72-1.06) for regular to high doses of aspirin use, 0.95 (0.80-1.13) for aspirin use 6+ times per week, and 0.93 (0.74-1.17) for aspirin use for 10+ years. For cumulative aspirin use, HR (95 % CI) was 0.87 (0.70-1.09) for > 60,000 mg of aspirin per year and 0.95 (0.75-1.21) for > 280,000 mg of aspirin in their lifetime, versus nonuse of aspirin. Results were similar for the all-cause cancer death as an endpoint, with a significant inverse association observed between lifetime aspirin dose and cancer mortality [< 95,000 mg vs nonuser HR 0.76 (0.61-0.95)]. These findings suggest that aspirin use may prevent incident breast, colon, pancreatic, and ovarian cancer in elderly women.