Can aspirin and fish oil reduce risk of bowel cancer? – results from the seAFOod trial

We asked Professor Mark Hull, from the University of Leeds, about the recently published seAFOod trial. Professor Hull gives us an overview of what the trial is, the key findings and what this means for people at higher risk of bowel cancer.

What is the seAFOod Trial?

The name seAFOod stands for ‘systematic evaluation of aspirin and fish oil’. The term relates to the fact that one of the substances we tested in the trial (EPA – an ‘omega-3’) is naturally found in fish.

seAFOod was a ‘polyp prevention trial’, in which we measured the number of bowel polyps (non-cancerous growths that can turn into cancer) as a marker of cancer risk. Patients, who had just undergone a colonoscopy (where a camera is used to look inside the bowel) and had several polyps removed, were randomly assigned to receive one of the following:

• EPA capsules (a daily dose roughly equivalent to eating about ten portions of oily fish like sardines or mackerel per week)
• a low-dose aspirin tablet
• both EPA and aspirin
• dummy capsules/dummy tablet (called a placebo)

The trial was blinded, which means none of the trial staff or the participants knew which treatment was being used by each individual.

What were the findings of the research?

Although EPA and aspirin did not decrease the number of patients with any bowel polyps, people who took EPA or aspirin were found to have fewer bowel polyps (between 10-20% less). We also found that EPA and aspirin work differently against different polyp types and depending on where the polyps were in the bowel.

On the whole both EPA and aspirin treatment were safe and well tolerated. EPA treatment caused a slight excess (about 10%) of mild abdominal symptoms including nausea and diarrhoea.      

What does this mean for people who have had polyps removed?

The results from this trial adds to what we already know about the potential benefits of taking aspirin for some people at higher risk of bowel cancer. This research suggests that aspirin (and to a lesser extent EPA) could reduce bowel cancer risk in patients who have already had multiple polyps removed and are at higher future risk of cancer.

What are the next steps for this research?

One important finding from the seAFOod trial is that the combination of EPA and aspirin together might be better than either alone. The seAFOod trial cannot give a definitive answer to this so another trial comparing combination treatment against aspirin on its own is needed. We will also be using samples collected during the trial to understand how EPA and aspirin work. We are also looking to develop a blood or urine test that could predict who is likely to gain most from taking EPA or aspirin. This may lead to even better ways of preventing bowel cancer.

• Find out more about the seAFOod trial (including a Participant Research Summary at the bottom of the page)
• Read the full academic research paper