Aspirin & cancer survival

Introduction

This is the third week in a row where I’ll declare an interest. I have met four of the authors on this week’s paper. The lead author, Professor Peter Elwood, was an examiner when I defended my PhD. Professor Elwood presided over one of the most well-known epidemiological studies – the Caerphilly Cohort study, which started in 1979 (Ref 1). I thought I was doomed with my findings that there was no evidence against total or saturated fat but he had found the same at the time. We both concluded that dietary fat guidelines had been introduced without evidence.

I met Janet Pickering with Peter once when we jointly explored the Caerphilly data to see if any other dietary associations could be observed. We concluded at the time that they couldn’t. I have met John Watkins a couple of times, as he and his wife are close friends of our neighbours. I also contacted John early in the epidemiology part of my PhD for advice, as he has worked in this field all his life. I met Christine Delon at the Public Health Collaboration conference in 2019 and we have emailed each other about research a few times since.

Peter has had many interests over many years, culminating in over 700 publications with his name on. He officially retired in 1995 but he was granted an honorary chair at Cardiff University, where he still goes to work. Peter quotes Archie Cochrane (founder of the Cochrane institute and his predecessor as Director of the MRC epidemiology unit) as saying “To treat a disease is an admission of failure, Prevention is the ultimate aim of medicine.” For over 50 years Peter’s research has been focused on the prevention of disease.

Alongside dietary fat and heart disease, another of Peter’s great interests has been aspirin. The summary description issued for a talk which Peter gave in March 2018 explained “Forty years ago a randomised controlled trial of aspirin in the prevention of heart attacks showed a 25% reduction in deaths and brought aspirin to the notice of cardiologists. Ten years later benefit was confirmed in one of the first ‘overviews’ conducted in medicine. In 2011 a series of follow-up studies of randomised trials showed a 40% reduction in cancer deaths and brought aspirin to the notice of oncologists. A reduction by aspirin in deaths and in the spread of cancer has been confirmed in numerous overviews.

But, aspirin is highly controversial. Its benefits in both vascular disease and cancer are widely acknowledged, but its dangers in increasing stomach bleeds are held by many to outweigh the benefits” (Ref 2).

Peter is an enthusiastic recipient of the Monday note and he invited me to review one of his recent publications (July 2021) entitled “Aspirin and cancer survival: a systematic review and meta-analysis of 118 observational studies of aspirin and 18 cancers” (Ref 3).

The title tells us so much already – it’s a huge study. It’s the best kind of evidence – a systematic review to find all the studies and then pooling them together in meta-analysis. It’s also looking at survival – which is what I would want to know had I had a cancer diagnosis. With the bizarre sense of evaluating the evaluator – here goes.