Linking Activity to Breast Cancer Survival
For post-menopausal breast cancer, there is strong evidence physical activity lowers the risk. Far fewer studies have looked at whether a lifetime of activity can help women once they are diagnosed with breast cancer. A new study led by former Marilyn Gentry Fellow Becki Cleveland, PhD, suggests it can.
An epidemiologist at the University of North Carolina at Chapel Hill, Cleveland's study looked at the activity patterns of approximately 1,500 women with breast cancer. Data was collected shortly after diagnosis, when the women reported all times they were active at least one hour per week for at least three months per year. After tracking the women for five years, the results are promising, says Cleveland.
Q: Your new study looks at the amount of recreational physical activity women did before a breast cancer diagnosis linked to longer survival. Can you explain what you mean as recreational physical activity?
A: Recreational physical activity is activity that is done for enjoyment or with the intention of exercise, outside of transportation, occupational or home obligations. Some examples are gardening, walking, golfing, dancing, bicycling, and tennis.
Q: Can you briefly describe the study?
A: Our study investigates how physical activity over the lifetime affects survival after a breast cancer diagnosis. We also wanted to examine whether there were particular periods within a woman's lifetime when physical activity is particularly beneficial in terms of protecting against death should she develop breast cancer.
Q: You looked at lifetime physical activity starting from early teenage years (after menarche) to diagnosis, correct? Why did you choose to start at menarche?
A: We chose to start at menarche because that is a time when there are a lot of hormonal changes taking place and it's when women begin to be exposed to higher levels of reproductive hormones, which are a key factor in breast cancer risk and survival. Several studies have shown that physical activity during adolescence can reduce the risk of breast cancer later. Physical activity is thought to delay puberty and decrease reproductive hormones, thereby reducing a woman's exposure to hormones over the lifetime.
Q: Can you describe/bottom line your findings? (Was it really *any amount of moderate activity over lifetime that linked to lower risk of death from any cause and breast cancer during the 5-year follow-up?)
A: Yes, we found that any amount of moderate regular exercise from menarche up to diagnosis reduced risk of both overall and breast cancer-specific death. We also saw a reduced risk for both pre- and postmenopausal women for engaging in any intensity of excercise, although for postmenopausal women this association was limited to physical activity that took place after menopause.
The risk reduction in mortality among the women who reported doing any pre-diagnostic recreational physical activity during their postmenopausal years compared to the women who did none was almost 40 percent.
Q: You also looked at how much activity women did 10 years prior to diagnoses and that also appears to lengthen survival. For women who didn't start exercising as teens/young adults, what did your findings show here?
A: For postmenopausal women in particular, it's not too late to start exercising to see benefits! We do see that a combination of more intense plus increased time spent exercising (>9 MET hrs/wk) leads to somewhat better survival than what we see for 0 to 9 MET hrs/wk, although survival is improved for that group too.
Q: What can women take away from your study, or is the research at too early of a stage to draw conclusions?
A: Our research findings are consistent with the few other studies showing improved survival with pre-diagnostic physical activity, and the message that women can take from our study in particular is very encouraging. We show that any amount of regular moderate recreational physical activity, particularly after menopause, will improve chances of survival after a breast cancer diagnosis. This means that in terms of breast cancer survival, women don't need to feel obligated to begin a high intensity and time-consuming exercise program to see benefits.
However, in order to fully benefit in terms of other chronic diseases such as heart disease and diabetes, women are still encouraged to engage in 2.5 hours of moderate of physical activity per week as recommended by the government [the Department of Health and Human Services].
A: Obesity is strongly linked to physical inactivity. In our previous research of obesity and breast cancer survival we found that there were specific time periods during the lifetime when obesity and weight gain were particularly associated with survival. So our next logical step was to evaluate the independent effects that physical activity has on survival over the lifetime as well. The results from both of these studies stress the importance of keeping a healthy body weight and engaging in moderate physical activity for reducing risk of death after a breast cancer diagnosis.
- Eur J Cancer Prev. 2011 Sep 22. [Epub ahead of print]
Influence of prediagnostic recreational physical activity on survival from breast cancer.
Cleveland RJ, Eng SM, Stevens J, Bradshaw PT, Teitelbaum SL, Neugut AI, Gammon MD.
- Read about Dr. Cleveland's previous work in an earlier issue of CRU.
- Watch video of Dr. Cleveland (right box #3)