Women who reported the highest levels of physical activity in the year before they were diagnosed with breast cancer may have higher survival, according to a new study.
Published in the October 15, 2006 issue of CANCER, a peer-reviewed journal of the American Cancer Society, the study found that obese and overweight women who had higher levels of moderate or vigorous recreational physical activity within one year before diagnosis tended to have better five-year survival patterns compared to other groups. Women of ideal body weight did not experience survival benefits from exercise; more remote histories of physical activity also had no impact on survival.
Identifying factors in cancer patients that predict outcome (i.e., prognosis) is important for physicians planning patient management and patients understanding their disease. In breast cancer, clinical indicators, such as tumor size, regional lymph node involvement, and estrogen-receptor status, have been shown to influence outcome. Other lifestyle factors, such as weight, may also predict disease course. While these factors are statistically associated with outcome to some degree, they may not explain all the variation which has lead researchers to search for additional prognostic factors, such as physical activity.
While exercise has been shown to be a significant factor in preventing breast cancer, its role in prognosis after diagnosis remains unclear but has also been infrequently studied. Page E. Abrahamson, Ph.D. now at the Fred Hutchinson Cancer Research Center in Seattle, led researchers while at the University of North Carolina, Chapel Hill to investigate the relationship between pre-diagnosis physical activity and survival in 1264 women with breast cancer.
The authors report that pre-diagnosis exercise did improve disease outcome. Survival modestly increased among women with body mass index (BMI) greater than 25 who reported highest levels of physical activity within one year of diagnosis. There was no benefit for women with BMI less than 25. Also, physical activity in adolescence or early adulthood had no impact on survival.
"Given that obesity is relatively well established as a poor prognostic factor in breast cancer," conclude the authors, "it is hopeful that activity may provide an opportunity to improve survival in this sub-population."