Conclusions: Making Decisions About Use and Dose
Medscape: When a decision is made that a patient should be taking aspirin, what dose is appropriate for primary prevention? The trials seem to use different doses.
Dr Hennekens: The risk of aspirin increases with the dose, but the Antithrombotic Trialists' Collaboration showed that there is no significant difference in the risks between 75 mg and 325 mg, and there is the same benefit. We have assumed that the lowest dose is the best because the side effects might be less. That complicates the situation more for the clinician because randomized trial evidence that used 325 mg suggests that aspirin prevents colon polyps from developing, and as secondary prevention in people with colon cancer, it reduces subsequent colon cancer risk.[28,29,30,31]
Medscape: At the ESC Congress, there was a question about how to evaluate the accumulating evidence for aspirin as protection again cancer, particularly colorectal cancer, and incorporate that with current recommendations in primary prevention of CVD.
Dr Hennekens: My position on cancer is the same as on CVD. I wouldn't want to see people so enthused about the early findings as to start giving people aspirin to prevent cancer, and then later on realize that the findings are not so conclusive. I believe that the cancer findings are not nearly as conclusive as they are in CVD, because the trials were not designed a priori to test cancer.
Medscape: Presumably we will also learn more about aspirin in cancer prevention in the coming years. The ASPREE trial, also looking at nonfatal cancer as a secondary endpoint, and a couple of other trials, including AspECT (Aspirin Esomeprazole Chemoprevention Trial), are focused on cancer prevention. Until then, mightn't physicians be tempted to give aspirin to people who are at increased risk for cancer, especially colorectal cancer?
Dr Hennekens: I would certainly consider it, but I would consider the cancer evidence as adjunctive to the CV evidence, not in isolation.
Medscape: For primary care providers, do you think it will be possible to produce a general guideline combining the benefits and risks of aspirin in preventing CVD and cancer?
Dr Hennekens: I have said—and I believe this to be over the course of decades—that guidelines for the use of aspirin in primary prevention are premature until we have the evidence. We don't have evidence yet for CVD, let alone in cancer, to, in my view, warrant routine guidelines. So I don't think we're helping clinicians at all to give them guidelines, let alone give them several that are not consistent with each other. Leave it up to individual clinical judgment.
Medscape: So would you advise clinicians to ignore current guidelines?
Dr Hennekens: The key thing about the guidelines is that we don't yet have a sufficient totality of evidence. Even when the totality of evidence is complete, guidelines should inform but not dictate the actions of clinicians.
Medscape: But we may expect to get evidence in a few years' time?
Dr Hennekens: Exactly. At present, let's just accept the uncertainties, and in a few years' time there is likely to be a more complete totality of evidence on aspirin in primary prevention. Until then, to paraphrase Voltaire, "Let's not let the perfect be the enemy of the possible."
Medscape Family Medicine © 2014 WebMD, LLC
Cite this: Does Aspirin Prevent Cardiovascular Disease and Cancer? Ignore the Guidelines - Medscape - Oct 29, 2014.