Image: A scanning electron photomicrograph (SEM) of prostate cancer cells (Photo courtesy of Prostate Cancer UK).
Prostate cancer affects more than 170,000 men each year in the USA, of who almost 30,000 die from the disease. While it is not yet known what causes the condition, a number of risk factors have been identified, such as age, ethnicity, and genetic mutations.
Male hormones, or androgens, such as testosterone are known to promote tumor cell growth in men with prostate cancer. Lowering or blocking testosterone levels in the body is the standard treatment for prostate cancer because androgens help the prostate cancer cells to grow.
A team of scientists led by those at University of Oxford (UK) examined 20 prospective studies including more than 19,000 men, 6,933 of who had prostate cancer and 12,088 of who were examined as healthy controls. Participants were aged between 34 and 76 years old, and their blood was collected for analysis between 1959 and 2004. The scientists grouped the men into 10 categories according to their testosterone level. These ranged from those with the lowest blood levels of the androgen to those with the highest.
The team reported that the men in the lowest testosterone group were considerably less likely to develop prostate cancer. In fact, they had a 20% reduced likelihood of developing the disease. Surprisingly, however, the study also found that if these men do end up developing the disease, they are 65% more likely to have an aggressive form of the condition. In the other nine groups of varying testosterone levels, the team found no association with prostate cancer risk.
Tim Key, BVM&S, MSc, DPhil, a professor and co-study author, said, “This is an interesting biological finding that could help us understand how prostate cancer develops and progresses. Until now, we didn't have a clear idea of the role testosterone played in prostate cancer risk. This is the first population study to support the theory that risk is lowered below a certain threshold of the hormone.” The study was presented at the National Cancer Research Institute (NCRI) Cancer Conference, held November 5-8, 2017, in Liverpool, UK.
University of Oxford