While discovery generated some excitement, “it wasn’t immediately clear how this would impact clinical practice,” says Ruth Langley, a professor of oncology and medical trials at University College London. It wasn’t obvious if the drug would have the same effect in humans, after all – meaning that the finding remained an obscure fascination rather than a potentially life-changing treatment.
A turning point came in 2010, when Peter Rothwell, a professor of clinical neurology at the University of Oxford in the UK, went back and re-investigated the much more abundant data on aspirin as a prevention of cardiovascular disease. In his analyses, the drug appeared to reduce both the incidence and spread of cancer, prompting renewed interest in both the power of aspirin to help fight the disease, and the reasons that it does so.
Proving that aspirin can prevent cancer in the general population is a challenge, however. In an ideal world, researchers would recruit a large sample of people. Half would take aspirin, while the rest would take a placebo pill – and you would then compare which had the highest rates of the disease. It can take many decades for cancer to occur in the first place, however, meaning that a randomised controlled trial would take a very long time to conduct at a huge expense. “It’s almost impossible, actually,” explains Anna Martling, a professor of surgery at the Karolinska Institute in Sweden.
For this reason, scientists have turned their attention to specific groups, such as those who have already had cancer or those who are genetically susceptible to developing it.
Mounting evidence
It is here that John Burn’s study of patients with Lynch Syndrome, which vastly increases the risk of colorectal and other forms of cancer, enters the picture. In 2020, Burn published the results of a landmark randomised controlled trial of 861 patients with the condition. Following the participants for 10 years, his team discovered that people who had taken a daily 600mg dose of aspirin for at least two years effectively halved their risk of colorectal cancer.
