Body weight and risk of prostate cancer – the WCRF perspective

In this Oncology Central exclusive, Dr Kate Allen, Executive Director Science and Public Affairs, World Cancer Research Fund International, gives her perspective on the latest evidence from their Continuous Update Project, which has revealed that men who are overweight or obese are at a greater risk of developing advanced prostate cancers.

More than 40,000 men are diagnosed with prostate cancer in the UK each year and over 10,000 die from the disease. Furthermore, many men live with the disease and the side effects of treatment for a long time. UK prostate cancer sufferers account for nearly a fifth of all cancer patients 5 years after diagnosis. This is, therefore, a hugely important disease.

The latest evidence from World Cancer Research Fund’s Continuous Update Project (CUP) ‘Diet, nutrition, physical activity and prostate cancer’ report has, for the first time, found a strong link between being overweight /obese and advanced prostate cancer. We estimate that approximately 10% of advanced prostate cancer cases in the UK could be prevented, if men kept a healthy weight.

In primary care there are issues about how best to tackle the disease. Difficulties start with the screening process. There have been concerns that screening with PSA testing can do more harm than good. On the other hand, men are understandably concerned about their prostate cancer risk and often want to be tested, regardless of any issues that may exist around the screening process.

Many men live with, rather than die from, prostate cancer. It is critical therefore, to identify those at most risk of developing a prostate cancer type that is likely to do them real harm if not treated.

We know a family history of prostate cancer increases risk and that black men are at higher risk than white or Asian men. However, there is still uncertainty in primary care as to which ‘lifestyle factors’ are involved in the risk profile of patients. A better knowledge of risk factors should enable prostate cancer screening to be targeted at higher risk patients, while providing some reassurance to those at less risk.

In terms of the findings from our report, we considered 104 separate cohort studies. The studies followed up a cohort of men, who were initially free of prostate cancer, for a number of years. In relation to the link between body fat and advanced prostate cancer, we looked at 24 studies. In 23 of those 24 studies, involving more than 11,000 men diagnosed with advanced prostate cancer, a statistically significant 8% increased risk of advanced prostate cancer was found, per 5kg / m2 of body weight. For prostate cancer mortality this rose to 11% increased risk. It is the first time we have been able to strongly link overweight / obesity with an increased advanced prostate cancer risk.

We think this finding could help inform the debate about the risk factors to be taken into account when considering whether screening is necessary. The research might also inform primary care workers when advising patients about the benefits of maintaining a healthy weight and being physically active.

A less consistent picture emerged in the research in relation to food and prostate cancer risk. In our report the evidence linking diets high in calcium to an increased risk of prostate cancer was downgraded from ’strong’ to ’limited’. Additionally, evidence that foods containing lycopene (such as tomatoes) decrease the risk of prostate cancer was downgraded from ’strong’ to no conclusion possible. Evidence that a diet higher in dairy products increases risk remains limited.

Our conclusions on nutrition have changed because more research has emerged since our last review of prostate cancer research in 2007.

More studies are separating out fatal, advanced or aggressive and non-advanced cancers. And while this has clarified what we know about prostate cancer and body fatness, it has clouded our understanding of the relationship between prostate cancer and certain foods.

Recent years have seen real progress in the study of prostate cancer, but it will be important to continue to improve the design of prostate cancer studies in future. Research that is able to accurately separate out the different prostate cancer types will be particularly valuable.

For now we hope our CUP report findings will help inform the wider debate about the risk factors linked to advanced prostate cancer and be of value to primary care professionals in their ongoing work with patients.

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