10 December 2015
By Dr Wendy Winnall - PCFA Research Team
A diagnosis with prostate cancer is often a life-changing moment. Men on active surveillance or those who've had an increase in PSA levels after radical prostatectomy live with the fear that their disease will progress. Exercise is a good way to improve your health, and some studies suggest that it reduces the risk of prostate cancer progression. The results of a recent small trial in Denmark support this idea.
The Danish study recruited men undergoing active surveillance as well as those with biochemical recurrence, defined as an increase in PSA levels after radical prostatectomy. These men performed 45 minutes of endurance training, three times a week for two years. They either ran, walked, rowed, swam or rode bicycles. After two years, they had lost an average of 3.6 kg, with improvements in fitness and reduction in body fat.
Since this was a small trial, with only 19 participants over two years, it wasn't possible to measure disease progression directly. Instead, the researchers used a measured called PSA doubling time as a 'surrogate marker' of prostate cancer progression. After only 6 months of endurance training, these men had a significant increase in PSA doubling time compared to those who did not train. This is a good outcome; it indicates that the exercise regime has slowed disease progression as the PSA levels are taking longer to increase.
An interesting finding from this study hints at the underlying biology of how exercise is increasing PSA doubling time. It was the VO2 max reading, not the loss of weight, that was associated with increased PSA doubling time. VO2 max, or maximal oxygen consumption, is a measure of physical fitness. This study therefore indicates that if you undergo endurance training and become fitter, but don't lose weight, this would still be beneficial. This is a small 'proof-of-principal' study that didn't compare the effects of different types or amounts of exercise. Much larger studies are necessary before physicians will know what type of exercise advice to give their prostate cancer patients.
This study, like most, has its own strengths and weaknesses. One of the strengths was the good study design. It was a 'prospective, randomised controlled trial' where the participants were randomly divided into endurance training and non-intervention groups then followed over time. This is an advantage, because you don't need to rely on the participants' memory of their past activity, they can fill in a daily logbook and undertake fitness tests during the study. Unfortunately the small number of participants made it difficult to detect more subtle differences between the groups, such as changes to absolute PSA levels. The small scale of the study also means it was not possible to directly test whether endurance training changed the risk of prostate cancer progression, they needed to use the PSA doubling time instead. The benefit of such studies is that they provide essential information that is needed for the design and funding of the larger, definitive trials.
There are now many small studies indicating the benefit of exercise for preventing prostate cancer, and for slowing the progression of the disease after diagnosis. While large studies are needed to define exactly what type of exercise to recommend, the evidence in favour of exercise to reduce the risk of prostate cancer progression is promising. If you've done little endurance training in the past, starting an intensive training regime later in life such can lead to injuries and other complications, so it's best to discuss your exercise plans with your doctor first.