"We found a beneficial effect on survival for exercise undertaken in the year before diagnosis, particularly among women who were overweight or obese near the time they were diagnosed with breast cancer," Dr. Page E. Abrahamson of the Fred Hutchinson Cancer Research Center in Seattle told Reuters Health.

The finding is encouraging, Abrahamson and colleagues note in the journal Cancer, because few modifiable lifestyle factors for improving a breast cancer prognosis have been identified.

Although survival rates for breast cancer generally are improving due to earlier detection and better treatments, "breast cancer patients are eager to know what they can do to enhance their survival," Abrahamson said.

Abrahamson and a multicenter U.S. team investigated the ties between prediagnosis physical activity and survival in 1,264 women, between 20 and 54 years old, who were diagnosed with breast cancer between 1990 and 1992.

Within several months of diagnosis, the women were asked about their average frequency of moderate and vigorous physical activity at age 13 years, age 20 years, and during the 12 months before diagnosis.

Two hundred ninety women died during the 8 to 10 years they were followed.

Data analysis showed that women reporting the lowest levels of activity had consistently lower survival rates throughout follow-up.

After accounting for stage of disease and income level, the researchers observed a modest overall reduced death risk of 22 percent among women in the highest quartile of activity in the year before their diagnosis compared with women in the lowest quartile of activity.

High activity levels were associated with a 30-percent reduction in the risk of death among women who were overweight or obese at the time of diagnosis.

No relationship was observed between mortality risk and physical activity levels among women who were underweight or at their ideal weight at the time of diagnosis. Physical activity at age 13 or age 20 also had no impact on survival in this study.

While exercise has been shown to be a significant factor in preventing breast cancer, this study is one of only a handful to look at the impact of physical activity on breast cancer survival. "More research in this area is warranted," Abrahamson said.

"If future research confirms that physical activity improves survival among women with breast cancer, programs and policies to promote such activity for this purpose may be adopted," she added.

SOURCE: Cancer, October 15, 2006.