Explain that among prostate cancer survivors, walking at a normal to brisk pace for at least 90 minutes a week appears to be associated with an almost 50% lower mortality risk.
A multivariable analysis showed that those men who reported any physical activity had a lower risk of all-cause mortality and prostate cancer-specific mortality.
Prostate cancer survivors can literally walk themselves to a lower risk of dying of the disease -- with some men achieving an almost 50% lower mortality risk, data from a large cohort study showed.
The study, involving more than 2,000 survivors of nonmetastatic prostate cancer, found those who walked at a normal to brisk pace for at least 90 minutes a week had a 46% lower mortality hazard -- and three or more hours of vigorous physical activity each week lowered the hazard to 49%, according to Stacey A. Kenfield, ScD, of the Harvard School of Public Health, and colleagues.
Walking had a nonsignificant but inverse relationship with prostate cancer-specific mortality, whereas three hours of vigorous activity was associated with a statistically significant 61% reduction in the hazard, Kenfield and co-authors wrote online in the Journal of Clinical Oncology.
"Our results suggest that among men with prostate cancer, moderate physical activity may improve overall survival, whereas a grater amount of activity is necessary to improve prostate cancer-specific survival," the authors concluded.
"Mechanistic studies and randomized trials of physical activity interventions are needed in prostate cancer survivors to determine whether physical activity reduces prostate cancer progression and what regimens are optimal," they added.
The current findings add to data from a previous report from the same group, showing an association between vigorous physical activity and a significant reduction in the diagnosis of advanced prostate cancer (Arch Intern Med. 2005;165:1005-1010).
That association led the team to hypothesize that vigorous physical activity might also reduce the risk of prostate cancer-specific and overall mortality in survivors of the disease, the most frequently diagnosed form of cancer among U.S. men.
To test their hypothesis, Kenfield and colleagues analyzed data from 2,705 men who participated in the Health Professionals Follow-Up Study. All participants had a diagnosis of nonmetastatic prostate cancer and were followed from 1990 to 2008. Follow-up included assessment of leisure-time activity every two years.
The questionnaire required the men to characterize the type, frequency, and duration of physical activity, using descriptions provided by the investigators. Each type of activity listed on the questionnaire had an associated metabolic equivalent task (MET) value. Self-reported activity was validated by one-week activity diaries that the men provided four times during follow-up.
During follow-up, 548 of the 2,705 men died, including 112 deaths resulting from prostate cancer. The median follow-up from first post-diagnosis assessment was 9.7 years for survivors and 7.8 years for men who died.
Walking accounted for 36% of total weekly MET-hours and 52% of total physical activity time. Heavy outdoor work accounted for 22% of weekly MET-hours and bicycling for 10%. Vigorous activity (MET value ≥6) contributed 37% of total MET-hours and 24% of total physical activity time.
A multivariable analysis showed that men who reported any physical activity had a lower risk of all-cause mortality (P<0.001) and prostate cancer-specific mortality (P=0.04).
Men who walked at least 90 minutes a week at a normal to brisk pace had a significant reduction in the all-cause mortality hazard (HR 0.54, 0.41 to 0.71) compared with men who walked shorter durations at a more leisurely pace.
Walking at a normal or brisk pace reduced the hazard for prostate cancer-specific mortality by 23% to 56%, depending on total walking time -- but the differences between leisurely or no walking at all did not reach statistical significance.
Vigorous physical activity modestly increased the overall-survival benefit observed with walking (HR 0.51, 0.36 to 0.72 versus ≤1 hour) and also reduced the hazard for prostate cancer-specific mortality as compared with one hour or less of vigorous activity (HR 0.39, P=0.03).
Kenfield and co-authors cited several limitations to the study, including that activity was self-reported and limited to a subset of common activities, a study cohort that was homogenous by profession, and their assessment of physical activity was a better measure of vigorous activity than of nonvigorous activity.
Even with those limitations, the group wrote that they "still observed a significant trend with increasing nonvigorous activity for all-cause mortality."
The study was supported by NIH, the Charles A. King Trust, and the Prostate Cancer Foundation.
The authors had no relevant disclosures.
Primary source: Journal of Clinical Oncology
Source reference:
Kenfield SA et al. "Physical activity and survival after prostate cancer diagnosis in the Health Professionals Follow-Up Study." J Clin Oncol. 2011;doi:10.1200/JCO.2010.31.5226.