The Women's Health Study - Aspirin vs Placebo in Cancer Prevention, JAMA (2005) [PubMed abstract]
  • The Women's Health Study enrolled 39,876 female healthcare professionals
Main inclusion criteria
  • Female ≥ 45 years old
  • No history of cancer (except nonmelanoma skin cancer), cardiovascular disease, or major chronic illness
Main exclusion criteria
  • Taking aspirin or NSAIDs more than once a week
  • Taking anticoagulants or corticosteroids
Baseline characteristics
  • Average age 55 years
  • Average BMI - 26
  • Current smoker - 13%
  • First-degree relative with breast, colorectal, or ovarian cancer - 18%
Randomized treatment groups
  • Group 1 (19,934 patients) - Aspirin 100 mg every other day
  • Group 2 (19,942 patients) - Placebo every other day
Primary outcome: Any cancer (excluding nonmelanoma skin cancer)

Duration: 10 years
Outcome Aspirin Placebo Comparisons
Primary outcome (any cancer) 7.2% 7.15% HR 1.01, 95%CI [0.94 - 1.08], p=0.87
Colorectal cancer 0.67% 0.68% HR 0.97, 95%CI [0.77 - 1.24], p=0.83
Lung cancer 0.45% 0.58% HR 0.78, 95%CI [0.59 - 1.03], p=0.08
Leukemia 0.19% 0.12% HR 1.54, 95%CI [0.92 - 2.57], p=0.10
Overall mortality 3.1% 3.2% HR 0.95, 95%CI [0.85 - 1.06], p=0.32
  • Aspirin did not significantly reduce the risk of any specific cancer
  • During the study, about 73% of patients were compliant with their assigned treatment [2]

Findings: Results from this large-scale, long-term trial suggest that alternate day use of low-dose aspirin (100 mg) for an average 10 years of treatment does not lower risk of total, breast, colorectal, or other site-specific cancers. A protective effect on lung cancer or a benefit of higher doses of aspirin cannot be ruled out.

  • Recommended dose is 81 mg once daily
  • *B - there is high certainty that the net benefit is moderate or there is moderate certainty that the net benefit is moderate to substantial; C - there is at least moderate certainty that the net benefit is small; I - insufficient evidence to recommend for or against
  • Increased risk of bleeding defined as dose of aspirin used, history of GI ulcers or upper GI pain, bleeding disorders, renal failure, severe liver disease, and thrombocytopenia. Other factors that increase risk include concurrent anticoagulation therapy or NSAID use, uncontrolled hypertension, male sex, and older age.
  • Reference USPSTF website
Aspirin for the primary prevention of cardiovascular disease and colorectal cancer
Age Recommendation
50 - 59 years Low-dose aspirin is recommended in patients who meet the following criteria:
  • 10-year risk of CVD of ≥ 10% (based on AHA risk calculator)
  • Not at increased risk of bleeding
  • Life expectancy of at least 10 years
  • Willing to take low-dose aspirin for at least 10 years
  • Grade B*
60 - 69 years
  • Decision should be individualized
  • Criteria for 50 - 59 year olds should be met
  • Grade C*
< 50 years or ≥ 70 years
  • Insufficient evidence to make recommendation
  • Grade I*

  • Reference [15]
AHA recommendations for daily low-dose aspirin in patients with a history of GI bleed/PUD
STEP 1 - Determine if patient has major risk factor for GI bleeding
  • Major risk factors include:
    • History of GI ulcers
    • History of GI ulcer complications (ex. bleeding)
      • If yes then patient should be tested for H. pylori infection and treated if indicated
    • History of GI bleeding
    • Patient taking dual antiplatelet therapy (Ex. aspirin + clopidogrel)
    • Patient also taking an anticoagulant (e.g. aspirin + warfarin)
STEP 2 - If any of the above are present, prescribe PPI with aspirin
  • Dose of aspirin should not exceed 81 mg a day
  • Enteric and buffered aspirin does not help (See enteric coated aspirin below)
STEP 3 - If none of the above are present, determine if other risk factors are present
  • Other risk factors include:
    • Age ≥ 60 years
    • Corticosteroid use
    • Stomach upset (dyspepsia) or GERD symptoms
STEP 4 - If two or more other risk factors are present, prescribe a PPI with aspirin
  • Dose of aspirin should not exceed 81 mg a day
  • Enteric and buffered aspirin does not help (See enteric coated aspirin below) [15]