[Physical activity for primary prevention of prostate cancer. Possible mechanisms]

Physical Activity and Prostate Cancer: An Updated Review

Prostate cancer affects a major proportion of older men, and effective preventive measures are few. Earlier suggestions of 10-30% risk reduction from vigorous physical activity thus merit further analysis. This narrative review updates information on associations between physical activity and prostate cancer, seeking activity patterns associated with maximal risk reduction. Systematic searches of Ovid/MEDLINE and PubMed databases from 1996 to June 2016 have linked the terms prostate neoplasms/prostate cancer with occupation, occupational title, sedentary job or heavy work, exercise, physical activity, sports, athletes, physical education/training or aerobic fitness. Combining these searches with findings from earlier reviews, 85 analyses were captured, although three were repeat analyses of the same data set. Seven analyses reported increased risk, and a further 31 showed no clear relationship. However, 24 analyses found a trend to diminished risk, and 21 a significant decrease (10-30% or more) in at least some subject subsets. Benefit was seen more consistently in occupational than in leisure studies, usually with adolescence or the early 20 s as the optimal age for preventive activity. In general, benefit showed a dose-response relationship, with vigorous activity required for maximal effect. Furthermore, several recent observational studies have indicated that physical activity is beneficial in preventing disease recurrence and improving survival following the diagnosis and treatment of prostate cancer. Despite continued research, conclusive proof of an association between regular physical activity and a low risk of prostate cancer remains elusive. However, reports that exercise exacerbates risk are few, and despite issues around controls, covariates, and co-morbidities, an impressive number of studies have now found significant benefit, suggesting that regular physical activity is important in terms of disease development, progression, and therapy. Given also the many other health benefits of an active lifestyle, it can be recommended as a potentially useful measure in the prevention of prostate cancer.

Latest Evidence on the Impact of Smoking, Sports, and Sexual Activity as Modifiable Lifestyle Risk Factors for Prostate Cancer Incidence, Recurrence, and Progression: A Systematic Review of the Literature by the European Association of Urology Section of Oncological Urology (ESOU)

CONTEXT

Smoking, sexual activity, and physical activity (PA) are discussed as modifiable lifestyle factors associated with prostate cancer (PCa) development and progression.

OBJECTIVE

To evaluate the available evidence concerning the association of smoking, sexual activity, and sports and exercise on PCa risk, treatment outcome, progression, and cancer-specific mortality.

EVIDENCE ACQUISITION

A systematic review of studies published between 2007 and 2017 using MEDLINE (via PubMed), Cochrane Central Register of Controlled Trials, and Web of Science databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis statement criteria was conducted.

EVIDENCE SYNTHESIS

While data concerning the impact of smoking on PCa development remain conflicting, there is robust evidence that smoking is associated with aggressive tumor features and worse cancer-related outcome, which seems to be maintained for 10 yr after smoking cessation. Less convincing and limited evidence exists for the association of sexual activity with PCa risk. The findings related to PA and PCa support the inference that exercise might be a useful factor in the prevention of PCa and tumor progression, while it is not finally proved under which specific conditions PA might be protective against disease development.

CONCLUSIONS

Smoking is associated with aggressive tumor features and worse cancer-related prognosis; as this negative impact seems to be maintained for 10yr after smoking cessation, urologists should advise men to quit smoking latest at PCa diagnosis to improve their prognosis. As several studies indicate a positive impact of exercise on tumor development, progression, and treatment outcome, it is certainly reasonable to advocate an active lifestyle. Least convincing evidence is available for the interaction of sexual activity and PCa, and well-conducted and longitudinal studies are clearly necessary to evaluate whether the suggested associations between PCa risk and sexual behavior are real or spurious.

PATIENT SUMMARY

In this systematic review, we looked at the impact of smoking, sexual activity, and sports and exercise on prostate cancer risk and outcome after treatment. While the evidence for sexual activity is not overall clear, we found that smoking might lead to more aggressive cancers and result in worse treatment outcome. Physical activity might prevent prostate cancer and improve cancer-related outcomes as well. Hence, it is certainly reasonable to advocate an active lifestyle and advise men to quit smoking.

Prostate Cancer Risk Reduced by Physical Activity Even Among Men With Prolonged Sitting Time: A Study From Vietnam

Increasing prostate cancer incidence in the Asia-Pacific region may be related to a more sedentary lifestyle resulted from economic growth and rapid urbanization. The present case-control study of 640 men aged 64 to 75 years was conducted in Vietnam between 2013 and 2015 to ascertain the relationship between physical activity and prostate cancer risk, accounting for the duration of sitting time. Reduced prostate cancer risks were found for men engaging in medium (15.8-47.3 metabolic equivalent task [MET]-h/week) and high (>47.3 MET-h/week) physical activity levels, with the adjusted odds ratios being 0.52 (95% confidence interval = 0.35-0.77) and 0.27 (95% confidence interval = 0.14-0.49), respectively. This association was independent of sitting time. Analyses of joint association of physical activity and sitting time also found a reduction in the cancer risk for higher energy expenditure levels. Similar results were evident for both low-medium and high grade tumors. The findings are important for developing health strategies to prevent prostate cancer in Asian countries.

Current opinion on the role of testosterone in the development of prostate cancer: a dynamic model

BACKGROUND

Since the landmark study conducted by Huggins and Hodges in 1941, a failure to distinguish between the role of testosterone in prostate cancer development and progression has led to the prevailing opinion that high levels of testosterone increase the risk of prostate cancer. To date, this claim remains unproven.

PRESENTATION OF THE HYPOTHESIS

We present a novel dynamic mode of the relationship between testosterone and prostate cancer by hypothesizing that the magnitude of age-related declines in testosterone, rather than a static level of testosterone measured at a single point, may trigger and promote the development of prostate cancer.

TESTING THE HYPOTHESIS

Although not easily testable currently, prospective cohort studies with population-representative samples and repeated measurements of testosterone or retrospective cohorts with stored blood samples from different ages are warranted in future to test the hypothesis.

IMPLICATIONS OF THE HYPOTHESIS

Our dynamic model can satisfactorily explain the observed age patterns of prostate cancer incidence, the apparent conflicts in epidemiological findings on testosterone and risk of prostate cancer, racial disparities in prostate cancer incidence, risk factors associated with prostate cancer, and the role of testosterone in prostate cancer progression. Our dynamic model may also have implications for testosterone replacement therapy.