Hot Topic From RxSchool

New Guidelines for Aspirin Use

Darrell Hulisz, RPh, PharmD
Sarah Hallisy,

May 3, 2016

The United States Preventive Services Task Force (USPSTF) recently released new guidelines regarding the use of aspirin as a primary prevention for cardiovascular disease (CVD) and colorectal cancer (CRC). The previous recommendations for CVD and CRC prevention using aspirin were last published in 2009 and 2007, respectively. The USPSTF found adequate evidence to support aspirin use as a primary prevention method to reduce risk for cardiovascular events, such as myocardial infarction (MI) or stroke, as well as a reduction in the incidence in CRC after 5-10 years of consistent use. Risks of using aspirin include an increase incidence of GI bleeds and hemorrhagic stroke. This risk is minimized in patients below the age of 70, but safety is not fully established in patients over the age of 70 with respect to bleeding risk.

The primary risk factors for CVD include older age, dyslipidemia, hypertension, diabetes, male gender, race/ethnicity, and smoking status. The USPSTF used the American College of Cardiology & American Heart Association 10-year ASCVD risk calculator to determine the patient's risk for ASCVD and the potential benefit of aspirin therapy, and this calculator may be found at the following site: http://clincalc.com/Cardiology/ASCVD/PooledCohort.aspx.

The USPSTF utilized a micro-simulation model taking into consideration baseline risk factors and aspirin use to provide an estimate of cardiovascular event rates. This model allowed for the analysis of non-fatal MIs, ischemic strokes, and cases of CRC prevented with aspirin therapy stratified by risk score, sex, and age, while also looking at the rate of bleeding events in each group. It considered 11 randomized controlled trials to evaluate CVD benefit, and 3 primary and secondary trials of CVD prevention to establish a 40% reduction in CRC incidence with use of aspirin daily.

Based upon this research the following recommendations are made:

1. Patients age <50: Unable to evaluate benefits versus risks. No recommendation made.
2. Patients age 50-59: Highest benefit group for daily low-dose aspirin (81mg) if ASCVD risk is greater than 10%, as benefits outweigh the harms if they do not have any other factors that would predispose them to bleeding. In addition, this group is more likely to experience benefit for CRC prevention due to life expectancy if they are willing to comply with daily aspirin therapy.
3. Patients age 60-69: Likely to benefit from aspirin therapy if ASCVD risk score is 10% or higher, as they are still expected to have a favorable benefit versus risk outlook. However, this group is less likely to experience benefit in regards to CRC prevention.
4. Patients age 70 or greater: Unable to evaluate benefits versus risks. No recommendation made.
5. No gender-specific recommendations were supported with respect to the above.

In the case of CRC prevention, the benefit of aspirin has not been seen until it has been consistently used for approximately 5-10 years. Therefore, if aspirin is being used for the sole indication of CRC prevention, patients with a lower life expectancy will be less likely to experience benefit from aspirin and patients between the ages of 50-59 are more likely to receive the benefit or preventative therapy. In conclusion, the success of aspirin as a preventive measure is dependent on bleeding risk, patient preferences on taking aspirin long-term, ASCVD risk score, and age. As cardiovascular disease and cancer are leading causes of death in the US, it is important to consider the use of aspirin therapy, particularly in patients age 50-59, to reduce the risk of disease development or progression.