Reference
Williams PT. Significantly greater reduction in breast cancer mortality from post-diagnosis running than walking. Int J Cancer. 2014;135(5):1195-202. Epub 2014 Feb 28.
Design
Cox proportional hazard analyses were used prospectively to compare breast cancer mortality to baseline exercise energy and to determine whether postdiagnosis running and walking differ significantly in their association with breast cancer mortality.
Participants
Data used in this analysis came from 272 runners and 714 walkers from the National Runners’ and Walkers’ Health Studies who were previously diagnosed with breast cancer. Diagnosis occurred (mean±standard deviation) 7.9±7.3 years before baseline. Forty-six women (13 runners and 33 walkers) died from breast cancer during the 9.1-year mortality surveillance.
Study Medication and Dosage
Metabolic equivalents (METs) per hour per day were calculated based on survey data.
Outcome Measures
Breast cancer–related mortality
Key Findings
When data from runners and walkers were evaluated together, the risk for breast cancer mortality decreased an average of 24% per MET hours per day of exercise, where 1 MET hour equals a little less than a mile of brisk walking or about two-thirds of a mile of running.
The possibility that such a simple intervention will prove useful in the long run is certainly intriguing.
When the runners and walkers were analyzed separately, there was significantly lower mortality in the runners. The runners’ risk for breast cancer mortality decreased over 40% per MET hour per day. Runners who averaged more than 2.25 miles per day were at 95% lower risk for breast cancer mortality than those that did not meet current exercise recommendations. In contrast, the walkers’ risk for breast cancer mortality decreased a nonsignificant 5% per MET hour per day.
Practice Implications
For the past half dozen years, we have strongly encouraged breast cancer patients to walk rigorously almost daily based on data from Irwin et al that suggested a possible 45% reduction in death rate.1 It was not clear back then that more exercise would be better. Based on this new paper by Williams, it seems we should be encouraging more rigorous exercise—running in fact, even suggesting an optimal distance of 2.25 miles per day.
Almost a quarter of women diagnosed with invasive breast cancer die within 15 years of diagnosis.2
Physical activity may improve survival in women diagnosed with breast cancer, but the evidence is mixed. A number of other studies have already shown that physical activity significantly reduces breast cancer mortality.1,3-7 Several other studies have not demonstrated a significant reduction.8-12 Still, when data are combined via meta-analyses, there is stronger evidence for improved survival with greater physical activity. For example data from 13,302 breast cancer survivors of the After Breast Cancer Pooling Project suggest that meeting the current physical activity recommendations is associated with a 25% reduction in breast cancer mortality.13 These recommendations for physical activity suggest that
all healthy adults aged 18 to 65 years need moderate-intensity aerobic (endurance) physical activity for a minimum of 30 min on five days each week or vigorous-intensity aerobic physical activity for a minimum of 20 min on three days each week.14
Two other meta-analyses reached similar conclusions. Patterson et al found a 29% reduction (including both physical activity measured for lifetime and at diagnosis),15 and Ibrahim et al found a 34% reduction16 in breast cancer mortality with postdiagnosis physical activity when various study results were combined.
There are aspects of this study that will be criticized—in particular the self-reporting of activity by the participants, absence of information on cancer stage at diagnosis, type of breast cancer participants had, and which treatment(s) the women underwent.
There is low risk of harm from encouraging more physical activity and encouraging greater exercise intensity in women who have been diagnosed with breast cancer. The possibility that such a simple intervention will prove useful in the long run is certainly intriguing. We now have reason, at least for the moment, to encourage these patients to take up running.
