Aspirin

In the myeloproliferative neoplasms, low-dose aspirin is given to almost everyone with polycythaemia vera and to low-risk and high-risk essential thrombocythaemia, because activated platelets cause both the microvascular symptoms (erythromelalgia, headache) and the arterial clots that drive mortality; the ECLAP trial in polycythaemia vera showed fewer combined cardiovascular events with aspirin. In prevention, the CAPP2 trial in Lynch syndrome found that 600 mg of aspirin a day for at least two years roughly halved colorectal cancers over the following decade, and long-term follow-up of cardiovascular trials suggested fewer colorectal cancer deaths. Against that, ASPREE, a trial in healthy adults over 70, found more cancer deaths on aspirin than placebo, so aspirin is not recommended for cancer prevention in older people without a specific indication. The Add-Aspirin trial is testing aspirin after treatment for breast, colorectal, gastro-oesophageal and prostate cancer. Its harms are bleeding, especially in the gut, and it must be avoided in essential thrombocythaemia with acquired von Willebrand deficiency.