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To Reduce Breast Cancer Recurrence Risk, Exercise—A Lot!

For protection against breast cancer recurrence, one recently reported study can best be described as “good news, bad news.”

At the American Association for Cancer Research Annual Meeting, researchers reported a statistically significant dose response for the effects of physical activity on breast cancer recurrence. The catch is that the effect was seen only among the most active tertile: women who exercised at least 20 hours a week.

Teresa Lehman, PhD, Chief Scientific Officer, Bio­Serve Technologies, Ltd, Beltsville, MD (a molecular biology service company with a repository of 600,000 tissue specimens), presented the study of 2435 patients surveyed and 215 who experienced a breast cancer recurrence.

“There is reasonable evidence that increased physical activity is associated with a reduced risk of breast cancer, but its role in the recurrence of breast cancer has not been established,” Dr Lehman said.

The study was a secondary analysis of data from the Global Epidemiological Study, a multinational study that assesses disease risk factors and is linked to this biorepository. Patients provided their personal history, including age, body mass index, and information on diet and physical activity. The study examined the association between physical activity and breast cancer recurrence.

Although the sample size was “relatively small,” Dr Lehman acknowledged, a significant effect was nevertheless observed.

Substantial Reduction in Recurrences

“On the univariate analysis, physical activity had a significant impact on recurrence, and on the multivariate analysis, after adjusting for age, body mass index, and cancer stage, the effect was even greater,” Dr Lehman said.

Subjects in the highest tertile of physical activity, who reported brisk walking and other moderate exercise for at least 20 hours a week, were 39% less likely to have a breast cancer recurrence, compared with women reporting no exercise (odds ratio [OR] = 0.61; 95% CI, 0.40-0.93). In the multivariate analysis, they were 45% less likely (OR = 0.55; 95% CI, 0.34-0.89). The dose-response relationship was statistically significant (P = .05), Dr Lehman reported.

Patients in the second tertile, who exercised 1 to 20 hours a week, actually had no reduction in recurrence risk (OR = 1.13 on the univariate analysis and 1.24 on the multivariate analysis). In the first tertile, the reference, women reported no brisk exercise.

Dr Lehman acknowledged that 20 hours of exercise is a challenge for most women. “You have to really make an effort to do this,” she said.

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