- By Rita Rubin
If you’re one of the millions of Americans who take low-dose aspirin to protect against a heart attack or stroke, chances are you’re also reducing your risk of colorectal cancer.
That’s the conclusion of the U.S. Preventive Services Task Force (USPSTF), an independent panel of health care professionals that, after reviewing the scientific evidence, makes recommendations about steps Americans can take to minimize their risk of disease and dying. Such steps include getting screened for cancer and taking preventive medications.
The USPSTF on Monday posted the draft of new guidelines about the use of aspirin by people 50 and older. They are the first from any major organization to recommend aspirin to prevent both cardiovascular disease and cancer. The public has until Oct. 12 to submit comments about the guideline.
“What we tried to do on this was to integrate the evidence on cardiovascular disease and cancer prevention,” said task force member Dr. Douglas Owens, a general internist and health services researcher at Stanford University.
The Human Toll
Cardiovascular disease is responsible for 30 percent of all U.S. deaths, the guideline notes, while colorectal cancer is the third most common cancer in the country. In 2014, an estimated 137,000 Americans were diagnosed with the disease and 50,000 died.
In its previous statement on the matter, the task force in 2007 recommended against the routine use of aspirin to protect against colorectal cancer by people at average risk for the disease.
The guideline is not a recommendation to take aspirin for cancer prevention if you are at low risk of cardiovascular disease.
— Dr. Douglas Owens, Stanford University
“The change in approach reflects the accumulation of scientific evidence about aspirin and lower risk of colorectal cancer,” Eric Jacobs, strategic director for pharmacoepidemiology at the American Cancer Society, said in a statement about the new guidelines (Jacobs is not a USPSTF member).
“There is more evidence about aspirin and colorectal cancer than there is about any other cancer,” Jacobs said. “However, there is also good evidence that aspirin use also lowers risk of developing esophageal cancer … and fairly good evidence for lowered risk of stomach cancer as well.”
No Scientific Consensus
Jacobs noted that the cancer society conducted the first major study on aspirin and colorectal cancer risk, back in 1991. Currently, though, the organization recommends against using aspirin or other nonsteroidal anti-inflammatory medications (NSAIDs), such as ibuprofen, to prevent colon cancer.
How aspirin protects against colorectal cancer isn’t clear, Jacobs said. Relatively high doses of aspirin reduce inflammation, which can be associated with cancer.
But even daily use of a “baby aspirin” — too small a dose to reduce inflammation in a measurable way — appears to lower colorectal cancer risk, he said. That suggests aspirin reduces cancer risk the same way it does heart attack risk, by interfering with platelets, cells in the blood that are highly sensitive to low doses of the drug, Jacobs said.
Not for Everyone
Owens emphasized that the USPSTF is recommending aspirin to protect against cancer only in people who, while not known to have cardiovascular disease, are candidates to take the medication because their 10-year risk of having a heart attack or stroke is high.
“The guideline is not a recommendation to take aspirin for cancer prevention if you are at low risk of cardiovascular disease,” said Owens.
The new USPSTF guideline recommends low-dose aspirin for the prevention of a first heart attack or stroke in adults 50 to 69 who have at least a 10 percent chance of developing cardiovascular disease over the next decade and are expected to live at least that long.
In addition, they should not be at an increased risk of digestive tract bleeding from taking aspirin. Risk factors for bleeding include a history of digestive tract ulcers or pain, bleeding disorders, kidney failure, severe liver disease and a too-low platelet count, according to the guideline.
Estimating Heart Disease Risk
The task force used a calculator based on research by the American College of Cardiology and the American Heart Association to estimate cardiovascular disease risk. The calculator considers such factors as race, gender, age, total cholesterol, HDL (“good”) cholesterol, blood pressure, use of blood pressure medication, diabetes status and smoking status.
(The heart association and the American Stroke Association recommend routine use of aspirin in adults whose 10-year risk of cardiovascular disease is 6 percent to 10 percent.)
Aspirin is most beneficial for people 50 to 59, according to the task force. For people 60 to 69 who meet the criteria for taking aspirin to protect against cardiovascular disease, the decision to go on low-dose aspirin is an individual one, because their risk of bleeding is greater than that of people in their 50s, the new guideline says.
The task force concludes that there is not enough scientific evidence to assess the balance of benefits and harms of aspirin to prevent heart attacks and strokes and colorectal cancer in adults either younger than 50 or 70 and older.
That represents a shift from the previous USPSTF guideline on aspirin and prevention of cardiovascular disease, released in 2009. At that time, the task force recommended aspirin for men age 45 to 79 and women 55 to 79.
But medical science is always evolving, and the evidence now suggests no major differences between the sexes in the potential harms and benefits of taking aspirin, Owens said.