Reference
Guy DE, Vandersluis A, Klotz LH, et al. Total energy expenditure and vigorous-intensity physical activity are associated with reduced odds of reclassification among men on active surveillance. Prostate Cancer Prostatic Dis. 2018;21(2):187-195.
Design
Retrospective comparison study
Objective
To examine the association between vigorous physical activity and disease progression in men on active surveillance for prostate cancer.
Participants
This study combines data from 2 cohorts of men. One group was recruited from the Sunnybrook Health Sciences Centre in Canada (SHSC) and the second group from the Royal Marsden Hospital in the United Kingdom (RMH). The SHSC group consisted of 131 men with favorable-risk prostate cancer and the RMH group consisted of 112 men with similar favorable-risk prostate cancer.
These 2 groups were divided into 2 subgroups: a) those who were undergoing active surveillance and b) those who were initially managed with active surveillance but were later reclassified to higher risk disease and subsequently underwent radical treatment. Those from either hospital whose cancer progressed and who were switched to radical treatment were “reclassified.”
Study Parameters Assessed
Physical activity was assessed by questionnaires. Association of physical activity was examined as a variable for risk of reclassification of status from surveillance to treatment. Demographic and lifestyle covariates were also analyzed to assess potential confounding and modification of exercise effect.
Key Findings
Total physical activity (recreational exercise plus work-related exercise) was inversely associated with odds of reclassification while on active surveillance (P trend=0.027). The trend for inverse association observed with recreational physical exercise alone did not reach statistical significance (P trend=0.30). Men who participated in weekly vigorous physical activity were significantly less likely to be reclassified than those who did not (odds ratio [OR]: 0.42; 95% confidence interval [CI]: 0.20-0.85). These inverse associations with total exercise were significant only when the data from both hospital cohorts were added together. If each cohort was examined separately the associations were only strong trends. Vigorous, high-intensity physical activity was significantly associated with a reduction in odds of reclassification in both cohorts.
Practice Implications
For men diagnosed with prostate cancer with low risk of progression it is now increasingly common to delay radical treatments (radiation or surgery) and instead just wait and watch to see if the disease progresses, a strategy known as active surveillance.1 This study is the first to look at the benefits of exercise for men with prostate cancer who are under active surveillance, and the results provide good reason to assume they will benefit from exercise. Prostate cancer often defies our educated guesses as to what will or will not provide benefit, so we prefer not to make assumptions based on other cancer types.
The bottom line that we want these patients to hear and remember is that men who exercise vigorously each week have a 58% lower risk of disease progression than men who don’t.
Based on this study we should encourage men under active surveillance to engage in exercise and these results suggest vigorous exercise provides greater benefit.
Several mechanisms have been suggested to explain the effects of exercise on prostate cancer progression.2 Increased physical activity reduces the availability of androgens and insulin-like growth factors.3,4 These hormones stimulate the androgen receptors on prostate tumor cells and trigger cell proliferation and cancer progression.5 There is also evidence that physical activity reduces the number of androgen receptors present on tumor cells.6
This was not a perfect study. It was retrospective and relies on patient recall for exercise intensity, duration, and frequency. It also relies on patient recall to adjust for possible confounders, in particular, other lifestyle factors, such as smoking or diet, that might impact risk. Yet until disproven by larger, more carefully performed studies, this is our only data that looks specifically at exercise and prostate cancer progression risk in the active surveillance population.
The bottom line that we want these patients to hear and remember is that men who exercise vigorously each week have a 58% lower risk of disease progression than men who don’t. Rounding those numbers for the sake of simplicity, one could say, “Exercise cuts your risk of disease progression by more than half.”
