By Paula Moyer
CHICAGO, IL -- June 8, 2007 -- Women who survive breast cancer and who were previously sedentary have lower insulin levels when they complete a prescribed exercise program, according to investigators who presented their findings here at the 43rd American Society of Clinical Oncology Annual Meeting (ASCO).
"We know that women who are overweight at the time of breast cancer diagnosis have a higher risk of recurrence than lean women," said principal investigator Jennifer Ligibel, MD, instructor of medicine, Harvard Medical School, and researcher, Breast Oncology Center, Dana-Farber Cancer Center, Boston, Massachusetts, United States.
Although the reasons are unclear, the findings suggest that physical activity has the potential to mediate breast cancer prognosis, she said.
Dr. Ligibel and her coinvestigators conducted their study to begin to elucidate the relationships by which body weight and physical activity influence breast cancer outcomes. Previous studies had shown that the high levels of insulin typical of obese and sedentary individuals are associated with an increased risk of breast cancer recurrence and breast cancer-related death. Dr. Ligibel and her team wanted to know whether exercise reduces insulin levels among breast cancer survivors.
For their study, they recruited 101 women with early-stage breast cancer who had completed adjuvant treatment, and who described themselves as being physically inactive. The women were randomised to a 16-week exercise intervention consisting of mixed cardiovascular and strength training exercises or to a standard care control group.
The target exercise goals included 2 supervised strength training sessions and 90 minutes of unsupervised cardiovascular exercise each week.
Participants' fasting insulin and glucose levels, as well as a measurement of their weight and body composition and the circumference at the waist and hip were collected at baseline and after 16 weeks.
Although the baseline insulin levels were similar in the 2 groups, they decreased by 2.86 mcIU/mL in the exercise group, a change that was statistically significant (P =.03), Dr. Ligibel said in her presentation on June 2nd. The controls' insulin levels decreased by 0.27 mcIU/ml, which was not statistically significant (P =.65).
When the investigators compared the changes in insulin levels across time, the differences between the groups approached statistical significance (P =.07).
The investigators also detected a trend toward improvements in insulin sensitivity in the exercise group (P =.09), although they detected no change in fasting glucose levels.
[Presentation title: Impact of Physical Activity on Insulin Levels in Breast Cancer Survivors. Abstract 555]
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