Even Modest Exercise May Decrease Breast Cancer Risk

MedicalResearch.com Interview with:
Dr Sylvie Mesrine, Gynecologist, MD
Inserm, CESP Centre for Research in Epidemiology and Population
Health, U1018, Nutrition, Hormones and Women’s Health Team,
Villejuif, France.

Medical Research: What are the main findings of the study?

Answer: We wanted to disentangle the effect of recent physical activity (within the
previous four years) from the effect of past physical activity (5-9 years
earlier) on postmenopausal breast cancer risk. Our most important finding
was that recreational/transport physical activity (including walking,
cycling and engaging in other sports), even of modest intensity, seemed to
have a rapid impact on breast cancer risk: it was quite rapidly associated
with a decrease in breast cancer risk, which was however attenuated when
activity stops. To our knowledge, our study is the first to independently
assess the association between breast cancer risk and recreational physical
activity both 5 to 9 years earlier and within the previous 4 years.
Furthermore, the association of recent recreational physical activity and
breast cancer risk decrease was observed whatever the recent levels of
gardening or do-it yourself activities.

Medical Research: Were any of the findings unexpected?

Answer:  The literature regarding the protective effects of recreational physical
activity for postmenopausal breast cancer is rather consistent, with
decreasing breast cancer risk associated with increasing levels of physical
activity. The World Cancer Research Fund / American Institute for Cancer
Research consider the association as “probable”, while the evidence is
considered as only “limited” among premenopausal women. However, the optimal frequency, duration and intensity of activity needed to reduce the risk are
unknown: inconsistent results have been reported regarding these aspects.
Therefore, our study added knowledge about how rapidly the protective effect
of physical activity on breast cancer is observed after regular physical
activity is initiated, and for how long it lasts after exercise stops.

Medical Research: What should clinicians and patients take away from your report?

Answer:  The main take away is for women: if they already exercise, they must be
encouraged to continue in order to keep the benefit of physical activity
regarding decreased breast cancer risk. And for those who do not exercise,
it is worth starting: their risk of breast cancer may decrease rapidly. It
is not necessary to engage in vigorous or very frequent activities: even
walking 30 minutes per day is beneficial (which is consistent with the World
Cancer Research Fund recommendations).

A clear public health message could strengthen women motivation to engage in
regular physical activity. So, it seems important that physicians and medias
could emphasize these messages.

Medical Research: What recommendations do you have for future research as a result of this study?

Answer:  One of the “provocative questions” identified by the National Cancer
Institute (http://provocativequestions.nci.nih.gov/ ) is “How does the
level, type, or duration of physical activity influence cancer risk and
prognosis?”. Indeed, regarding breast cancer, the World Cancer Research Fund
/ American Institute for Cancer Research consider the protective effect of
physical activity as “probable”, while the evidence is considered as only
“limited” among premenopausal women. Thus studies are still needed to
determine what features or types of physical activity are most important in
achieving these benefits, and what is the mechanism underlying these


Postmenopausal breast cancer risk decreases rapidly after starting regular
physical activity

A. Fournier, G. Dos Santos, G. Guillas, J. Bertsch, M. Duclos, M.-C. Boutron-Ruault, F. Clavel-Chapelon, S. Mesrine. Recent Recreational Physical Activity and Breast Cancer Risk in Postmenopausal Women in the E3N Cohort. Cancer Epidemiology Biomarkers & Prevention, 2014; DOI: 10.1158/1055-9965.EPI-14-0150