EAU 2017: Special session of the Prostate Cancer Prevention Group - Risk factors and biomarkers for screening and triage: Dietary and lifestyle factors
Before delving into dietary association with prostate cancer, Dr. Key also mentioned the proven association of height to cancer in general. In regards to prostate cancer, the data has not been entirely clear. Data from the EPIC study showed no association between prostate cancer and height, after analysis of 7000 cases. There is significant heterogeneity by grade with taller men having a greater chance of having lethal disease.
In regards to body mass index (BMI) and prostate cancer, it was shown that men with higher BMI have a lower risk of prostate cancer. Similar to height, there is heterogeneity by grade with a higher risk for lethal cancer in men with high BMI. When looking at the association of height and BMI using the genetic field, no significant association to prostate cancer was seen.
Dr. Key also elaborated on the association of major food groups to prostate cancer. Through large datasets of patients it was found that meat, poultry and fish were not correlated to prostate cancer. Consumption of dairy product protein was found to possibly have a correlation to high risk prostate cancer. When looking at fruit and vegetables – little association was found with a small significant inverse relationship between fruit and prostate cancer, but not for vegetables. Both fruit and vegetables did not have grade heterogeneity.
There are nutritional biomarkers in the blood which are available and can be used to overcome some of the problems encountered with using questionnaires. An example he used was fatty acids derived from plants and long chain fatty acids, including Omega 3. All fatty acids including Omega 3, thought to protect from cardiovascular disease, were not found to have an association with prostate cancer.
Six types of carotenoids including Lycopene and their association to prostate cancer have been studied as well. No evidence of any protective role from prostate cancer was witnessed. However, with Lycopene an inverse association was noticed with higher levels correlated with lower risk of being diagnosed with prostate cancer. Alpha tocopherol (vitamin E) was found also to have an inverse association in advanced but not localized prostate cancer. However, randomized controlled trials did not show any association of prostate cancer to Alpha tocopherol.
In regards to Selenium – toe nails provide better information regarding tissue absorbed levels than blood samples. No association was found with prostate cancer when levels were measured in the blood, but an inverse relationship was demonstrated when correlated to levels measured in the toe nails. However, similar to Alpha tocopherol, randomized controlled studies (SELECT trial) did not find any benefit for Selenium.
Folate and vitamin B-12 do cause a small increase in the risk of prostate cancer. Similarly, randomized controlled trials of folate also found borderline significant increase in risk. With regards to insulin growth factor (IGF), 5 types were looked at with a strong association found with IGF-1. It is hypothesized that the more dairy products are eaten, the higher the level of IGF-1 is in the blood, and therefore dairy product protein might cause an in increase in the risk of prostate cancer, as mentioned before.
When looking specifically at vegetarian people who do not eat animal protein, there is some evidence to suggest they have a lower risk of prostate cancer.
To conclude, there is substantial evidence that obesity increases the risk of more aggressive disease. Suggestive protective associations for Lycopene, Alpha-tocopherol and selenium for advanced stage disease merit further study. Changes in diet composition such as reduction in dairy protein, might reduce IGF-1 and thus cancer risk. More data from genetic studies using Mendelian Randomization should help clarify causality of some associations.
Presented by: Timothy J. Key, Oxford (GB)
Written by: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto
Twitter: @GoldbergHanan
at the #EAU17 -March 24-28, 2017- London, England