“Prostate cancer is the second most commonly diagnosed cancer in men worldwide after lung cancer and a leading cause of cancer death. But there is no evidence-based advice that we can give to men to reduce their risk,” says Dr. Ruth Travis, an Associate Professor, and Ellie Watts, a Research Fellow, both based at the University of Oxford. “We were interested in studying the levels of two hormones circulating in the blood because previous research suggests they could be linked with prostate cancer and because these are factors that could potentially be altered in an attempt to reduce prostate cancer risk.”
Participants were part of the UK Biobank Project, were not taking any hormone therapy and were free of cancer when they were enrolled in the study. Blood samples were taken to test for levels of testosterone and IGF-1; and a subset of 9,000 men provided blood additional samples at a later date to help account for natural fluctuation in hormone levels. Participants were followed for on average 6-7 years in which 5,412 cases and 296 deaths from the disease occurred.
Those with higher concentrations of the two hormones in their blood were found to be more likely to be diagnosed with prostate cancer; for every increase in IGF-1 concentration per litre of blood men were 9% more likely to develop prostate cancer, and for every increase of 50 picomoles of free testosterone per liter of blood there was a 10% increase in risk for prostate cancer. As a population whole findings correspond with a 25% increased risk in men with the highest levels of IGF-1, and men with the highest levels of free testosterone levels have an 18% increased risk of prostate cancer.
According to the researchers because the blood samples were taken many years before they developed prostate cancer it is likely that hormones levels are what is leading to the increased risk of prostate cancer as opposed to the cancers leading to the increased levels. The large size of the study allowed for the consideration of other factors that could also influence the risk of cancer including BMI, diabetes, and socioeconomic status.
“This type of study can’t tell us why these factors are linked, but we know that testosterone plays a role in the normal growth and function of the prostate and that IGF-I has a role in stimulating the growth of cells in our bodies. What this research does tell us is that these two hormones could be a mechanism that links things like diet, lifestyle and body size with the risk of prostate cancer. This takes us a step closer to strategies for preventing the disease,” explains Travis.
“These results are important because they show that there are at least some factors that influence prostate cancer risk that can potentially be altered. In the longer term, it could mean that we can give men better advice on how to take steps to reduce their own risk.This study also shows the importance of carrying out very large studies, which are only possible thanks to the thousands of men who agreed to take part,” said Professor Hashim Ahmed, chair of NCRI’s prostate group and Professor of Urology at Imperial College London.
