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Authors Kenfield SA, Stampfer MJ, Giovannucci E, Chan JM.
Review Date Jun 2011
Citation Journal of Clinical Oncology 2011;29:726-732
Physical activity has been shown to be associated with a lower incidence of advanced prostate cancer and has been linked to reduced cancer-specific and overall mortality in breast and colon cancer. Given that many men live for years after a prostate cancer diagnosis, the possible survival benefit of physical activity following diagnosis is of considerable interest.
To determine whether higher physical activity after prostate cancer (PCa) diagnosis decreases risk of overall and PCa-specific mortality.
This study evaluated physical activity in relation to overall and PCa mortality among 2,705 men in the Health Professionals Follow-Up Study diagnosed with nonmetastatic PCa observed from 1990 to 2008. Proportional hazards models were used to evaluate physical activity and time to overall and PCa-specific death. Multivariable analysis adjusted for age, age at diagnosis, months since diagnosis, clinical stage, Gleason score, treatment, parental history of myocardial infarction at age 60 or younger, high blood pressure, high cholesterol, diabetes status, smoking, body mass index, alcohol intake, and co-morbidities measured prior to physical activity measure.
Among men who lived at least 4 years after their post-diagnosis physical activity assessment, 548 deaths were documented – 112 (20%) were a result of PCa. The median time from diagnosis to first physical activity assessment was 18 months. Median duration of follow-up time from first post-diagnosis physical activity assessment to either death, or censoring in January 2008, was 9.7 years for survivors and 7.8 years for men who died.
In multivariable analysis, men who were physically active had lower risk of all-cause mortality (P(trend) < 0.001) and PCa mortality (P(trend) = 0.04). Both nonvigorous activity and vigorous activity were associated with significantly lower overall mortality. Those who walked ≥ 90 minutes per week at a normal to very brisk pace had a 46% lower risk of all-cause mortality (hazard ratio [HR] 0.54; 95% CI, 0.41 to 0.71) compared with shorter durations at an easy walking pace. Men with ≥ 3 hours per week of vigorous activity had a 49% lower risk of all-cause mortality (HR, 0.51; 95% CI, 0.36 to 0.72).
For PCa-specific mortality, brisk walking at longer durations was suggestively inverse but not statistically significant. Men with ≥ 3 hours per week of vigorous activity had a 61% lower risk of PCa death (HR, 0.39, 95% CI, 0.18 to 0.84; P = .03) compared with men with less than 1 hour per week of vigorous activity. Men exercising vigorously before and after diagnosis had the lowest risk.
In men with PCa, physical activity was associated with lower overall mortality and PCa mortality. A modest amount of vigorous activity such as biking, tennis, jogging, or swimming for ≥ 3 hours a week may substantially improve PCa-specific survival.
Points to Note
- The authors tried to exclude reverse causation (that is, undiagnosed metastatic PCa causing men to reduce physical activity) as an explanation for the results by excluding men with metastases at diagnosis and up to 2 years after their first post-diagnostic physical activity assessment, men who died within 4 years of this assessment, and by using activity information 4 to 6 years before death (median time from metastases to death was 2 years).
- The limitations of the physical activity measure were that it was self-reported and included only a sub-set of common activities. However this measure has detected other well established activity-disease relationships so the authors believe it is valid.
- Intervention studies in men following a prostate cancer diagnosis are needed to determine whether physical activity reduces prostate cancer progression, hence leading to better survival, and what exercise regimens are optimal.