Exercise could lower breast cancer recurrence risk and insulin levels in survivors

Issue: April 10, 2008

Engaging in exercise could be related to a significant decrease in insulin levels and hip circumference in breast cancer survivors, according to recent data.

“There is probably a lot that happens when people begin to exercise that may influence cancer recurrence risks, and we are at the cusp of figuring out how something like physical activity impacts breast cancer recurrence risk,” Jennifer A. Ligibel, MD, instructor of medicine, Harvard Medical School, told HemOnc Today.

“We are a step away from an actual recommendation for patients with breast cancer. There are a lot of [data from] observational studies that suggest that physical activity is a good thing for women who have had breast cancer,” she said. (Click here to read more of HemOnc Today's interview with Dr. Ligibel.)

Most oncologists do not spend time talking to their patients about physical activity, according to Ligibel.

Researchers at the Dana-Farber Cancer Institute and Harvard Medical School indicated that the link between breast cancer prognosis and physical exercise could be mediated, partially by insulin level changes and/or fat deposition or body fat changes.

Researchers assigned 101 inactive and overweight breast cancer survivors to a 16-week cardiovascular and strength training exercise regimen or to a control group that was administered standard care. At both baseline and after 16 weeks, weight, circumference at the hip and waist, fasting insulin and glucose levels, and body composition data were accumulated.

In 82 patients with both baseline and 16-week measurements, fasting insulin concentrations were lowered by an average of 2.86 mcU/mL (P=.03) in the exercise arm, whereas a significant change was not reported in the control group (decrease of 0.27 mcU/mL; P=.65).

Though the researchers reported that the insulin level changes in the exercise arm appeared to be larger in the control arm, the assessment was not statistically significant.

A trend indicating improved insulin resistance in the exercise arm (P=.09) was reported, although fasting glucose levels did not change. Data showed that patients in the exercise arm had decreased circumference measurements (P=.02) though their body composition and weight did not change.

Ligibel said that the evidence until now that indicated lower recurrence has been observational.

“Eventually we will need to not only figure out what happens when people begin to exercise, but really show through randomized trials that it is exercise that is making the difference and not something else that these women are doing,” Ligibel said. – by Paul Burress

For more information:
Ligibel JA, Campbell N, Partridge A, et al. Impact of a mixed strength and endurance exercise intervention on insulin levels in breast cancer survivors. J Clin Oncol. 2008;26:907-912.