Men with higher levels of free (biologically active) testosterone and insulin-like growth factor-1 (IGF-1) in their blood are more likely to be diagnosed with prostate cancer, according to research presented by Travis et al at the 2019 National Cancer Research Institute (NCRI) Cancer Conference. The new study of more than 200,000 men is one of the first to show strong evidence of two factors that could possibly be modified to reduce prostate cancer risk.
The research was led by Ruth Travis, MSc, DPhil, Associate Professor, and Ellie Watts, a research fellow, both based at the University of Oxford.
Dr. Travis explained, “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.”
The researchers studied 200,452 men participating in the UK Biobank project. All were free of cancer when they joined the study and were not taking any hormone therapy.
The men gave blood samples that were tested for their levels of testosterone and IGF-1. The researchers calculated levels of free testosterone from measured total testosterone and binding protein concentrations. A subset of 9,000 of men gave a second blood sample at a later date, to help the researchers account for natural fluctuations in hormone levels.
The men were followed for an average of 6 to 7 years to see if they went on to develop prostate cancer. Within the group, there were 5,412 cases and 296 deaths from the disease.
The researchers found that men with higher concentrations of the two hormones in their blood were more likely to be diagnosed with prostate cancer. For every increase of 5 nanomoles in the concentration of IGF-1 per liter of blood (5 nmol/L), men were 9% more likely to develop prostate cancer. For every increase of 50 picomoles of free testosterone per liter of blood (50 pmol/L), there was a 10% increase in prostate cancer risk.
Looking at the population as a whole, the researchers say their findings correspond to a 25% greater risk in men who have the highest levels of IGF-1, compared to those with the lowest. Men with the highest free testosterone levels face a 18% greater risk of prostate cancer compared to those with the lowest levels.
The researchers say that because the blood tests were taken some years before the prostate cancer developed, it is likely that the hormone levels are leading to the increased risk of prostate cancer, as opposed to the cancers leading to higher levels of the hormones. Due to the large size of the study, the researchers were also able to take account of other factors that can influence cancer risk, including body size, socioeconomic status, and diabetes.
Dr. Travis said, “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-1 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.”
Disclosure: For full disclosures of the study authors, visit abstracts.ncri.org.uk.The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.