NEW ORLEANS — Greater physical activity before and after cancer diagnosis significantly decreased risk for prostate cancer-specific mortality, according to an analysis of the Cancer Prevention Study II Nutrition Cohort presented at the American Association for Cancer Research Annual Meeting.
Results also showed a decreased mortality risk among men whose only physical activity was walking.
“The American Cancer Society recommends adults engage in a minimum of 150 minutes of moderate or 75 minutes of vigorous physical activing per week,” Ying Wang, PhD, senior epidemiologist at the Epidemiology Research Program of the American Cancer Society, said in a press release. “These results indicated that following these guidelines might be associated with better prognosis.”
Wang and colleagues sought to investigate the relationship between exercise and prostate cancer-specific mortality before and after diagnosis of nonmetastatic prostate cancer.
The analysis included data from 10,067 men enrolled in the Cancer Prevention Study II Nutrition Cohort who received a nonmetastatic prostate cancer diagnosis from the time they entered the cohort (1992 or 1993) until June 2011.
Men self-reported the amount of time they were engaged in physical activity — which included walking, dancing, bicycling, aerobics, jogging or running, lap swimming, tennis or racquetball — and the amount of time spent sitting.
Researchers calculated metabolic equivalent (MET) activity hours per week based on the self-reported data.
Six hundred men died of prostate cancer during follow-up through 2012.
Overall, men who reported more than 17.5 MET activity hours per week — which is equivalent to 5 hours of walking and twice the minimum of physical activity recommendations — experienced a reduction in mortality risk compared with men who reported 3.5 or fewer MET activity hours per week. Specifically, 17.5 MET activity hours per week prior to cancer diagnosis conferred a 30% reduction in risk for prostate cancer-specific mortality (HR = 0.7, 95% CI, 0.54–0.92) and 17.5 MET activity hours per week after diagnosis conferred a 34% decreased risk (HR = 0.66, 95% CI, 0.46-0.93).
Forty percent of men in the cohort reported walking to be their only form of exercise.
Men who reported 4 to 6 hours of walking each week prior to their cancer diagnosis demonstrated a 33% lower risk for prostate cancer-specific mortality (HR = 0.65, 95% CI, 0.46-0.91) and men who reported more than 7 hours of walking each week demonstrated a 37% lower risk (HR = 0.6, 95% CI, 0.41-0.88). However, this association did not persist when researchers evaluated walking after diagnosis.
The researchers also studied the impact of sitting time and found that it was not associated with prostate cancer-specific mortality.
Wang and colleagues acknowledged the self-reported nature of the data as a possible limitation. Also, the study did not adjust for vigorous exercise vs. leisure exercise, despite past research suggesting vigorous exercise is associated with lower prostate cancer-specific mortality risk.
“Our results support evidence that prostate cancer survivors should adhere to physical activity guidelines, and suggest that physicians should consider promoting a physically active lifestyle to their prostate cancer patients,” Wang said. – by Nick Andrews
Wang Y, et al. Abstract 1736. Presented at: American Association for Cancer Research Annual Meeting; April 16-20, 2016; New Orleans.
April 23, 2016