Study adds evidence in favor of physical activity
Normally sedentary breast cancer survivors who completed an exercise
program reduced the levels of insulin in their blood, revealing a likely
link between physical activity and better outcomes, researchers from
Dana-Farber Cancer Institute in Boston reported at the annual meeting of
the American Society of Clinical Oncology in Chicago.
Although it was previously demonstrated that women who lost weight
and became more active could lower their risk of breast cancer
recurrence, scientists couldn't explain how it worked.
Jennifer Ligibel, MD, of Dana-Farber, and her colleagues' research
findings support the hypothesis that exercise lowers levels of the
hormone insulin in the bloodstream. Studies have found an association
between relatively high levels of insulin — often seen in obese and
sedentary people — and an increased risk of breast cancer recurrence and
breast cancer-related death.
"We know that women who are overweight at the time of breast cancer
diagnosis have a higher risk of recurrence than lean women, but the
reasons for this have not been clear," said Ligibel, of the Breast
Oncology Center at Dana-Farber. The association with insulin has emerged
from recent observations.
In the new study, researchers measured insulin and blood glucose
levels in 101 women as well as their weight, body composition, and
circumference of the waist and hips. Half were assigned to a 16-week
regimen of mixed cardiovascular and strength training, while the other
half had normal care.
At the end of the experiment, the women who exercised had lowered
their insulin measurements by an amount that approached statistical
significance. There was also a statistical trend to improved insulin
sensitivity (how the body responds to insulin) in the exercise group.
The more-active women had a reduction in hip circumference as well.
"Our findings suggest that the effects of exercise on breast cancer
prognosis may be mediated, at least in part, through changes in insulin
levels and/or changes in fat mass or deposition," said Ligibel.
"Exercise has benefits all through treatment and afterwards. It's an
investment in a woman's health and hopefully will prove to lower her
risk of dying from breast cancer."
The study's senior author is Eric Winer, MD, of Dana-Farber. The
other authors include Nancy Campbell, MS, Wendy Chen, MD, Taylor
Salinardi, and Ann Partridge, MD, MPH, of Dana-Farber; and Christos
Mantzoros, MD, of Beth Israel Deaconess Medical Center.
Dana-Farber Cancer Institute (www.dana-farber.org)
is a principal teaching affiliate of the Harvard Medical School and is
among the leading cancer research and care centers in the United States.
It is a founding member of the Dana-Farber/Harvard Cancer Center
(DF/HCC), designated a comprehensive cancer center by the National