Physical Activity After a Diagnosis of Breast Cancer

 

 

Behind the Cancer Headlines®

May 1, 2003

 

 

Women diagnosed with breast cancer are less physically active after diagnosis than prior to diagnosis, which may contribute to a poorer prognosis.

 

Findings in a recent NCI supported study published in the journal Cancer indicate that most women diagnosed with breast cancer exercise or engage in any sort of physical activity an average two hours a week less after diagnosis than before diagnosis, marking an 11% decrease.

 

Women who were already obese before diagnosis or who received the most intensive breast cancer treatment, including surgery, chemotherapy and radiotherapy, reported the most significant decline in physical activity after diagnosis.

 

The authors conclude that "decreases in physical activity with a diagnosis of breast cancer may lead to increases in body weight and body fat, which, in turn, may lead to a poorer breast cancer prognosis." The paper's lead author, Melinda Irwin, Ph.D., M.P.H., an assistant professor in the Department of Epidemiology and Public Health at Yale School of Medicine, conducted the research while a postdoctoral fellow at the Fred Hutchinson Cancer Research Center in Seattle. The study also involved researchers from the National Cancer Institute, the University of New Mexico and the University of Southern California.

 

The role of weight and body fat in the prognosis of breast cancer is important. A woman who is overweight with elevated body fat at the time of diagnosis has a poorer prognosis with increased risk of recurrence and poorer survival than a woman of normal body weight and body fat. Scientists hypothesize that because fat cells produce estrogens after a woman goes through menopause, having higher levels of body fat at breast cancer diagnosis or experiencing weight gain following diagnosis may be associated with a worse prognosis, since estrogens stimulate breast cancer cells. However, scientists know almost nothing about the role of weight gain on prognosis after a breast cancer diagnosis.

 

Weight gain and subsequent increased body fat affects more than 80% of women during the first year after breast cancer diagnosis. Multiple reasons for weight gain have been proposed but never proven, such as the therapy, increased caloric intake and decreased physical activity. Though treatment may have a negative impact on physical activity, studies show that even women undergoing intensive therapy for breast cancer are able to be physically active during this first year.

 

Irwin et al investigated how physical activity for 856 women changed for 4-12 months after breast cancer diagnosis compared to the year before diagnosis and whether there was any association with the severity of disease, the type of treatment, age and body mass index.

 

Most women reported being less physically active after diagnosis for all stages of breast cancer. On average women reported a 2.0-hour per week decline in all types of physical activity after diagnosis, representing an 11% decrease from pre-diagnosis levels. "This decrease in physical activity most likely explains some of the weight gain observed after cancer diagnosis," the authors note.

 

Women who were treated with the most intensive therapy (surgery, radiation and chemotherapy) reported a 50% decline in physical activity compared to a 24% decline among women treated with surgery only and a 23% decline among women treated with radiation only. Physical activity among obese women declined 41% after diagnosis compared to a 36% decline among overweight women and a 24% decline among women with a normal body mass index.

 

In designing a treatment program for cancer patients that includes exercise, efforts "should focus on maintenance of activity levels among previously active breast cancer survivors and increasing physical activity among inactive breast cancer survivors."

 

The authors conclude that the "data on physical activity levels among breast cancer patients provide valuable information for planning larger observational and intervention studies designed to evaluate how physical activity levels may improve prognosis and prolong survival."

 

 

SOURCE:

 

Cancer, April 1, 2003