Women with invasive breast cancer and high blood levels of C-peptide (a marker of insulin secretion often associated with obesity and overweight) face a risk of death from the disease that's nearly three times higher than women with lower blood levels of C-peptide.
The findings come from the Health, Eating, Activity and Lifestyle (HEAL) Study, a long-term, multi-center observation of breast-cancer patients. Dr. Anne McTiernan of the Public Health Sciences Division co-led the study, which involved more than 200 western Washington breast-cancer survivors.
Previous research has demonstrated that insulin stimulates the growth of breast-cancer cells in the laboratory, but few studies have examined the link between fasting insulin or C-peptide levels and breast-cancer prognosis.
The researchers found that women with invasive breast cancer — meaning the cancer had spread throughout the breast tissue or to surrounding tissues — faced the greatest risk from high C-peptide levels, but the association was detected in nearly all women studied, regardless of whether their cancer had spread. These findings were recently presented in Philadelphia at the American Association for Cancer Research's Sixth Annual International Conference on Frontiers in Cancer Prevention Research.
McTiernan said that based on these results it is important for breast-cancer patients to be aware of their insulin levels and, if they are elevated, to take steps to lower them through lifestyle factors such as regular physical activity, weight control, and eating a low-fat diet rich in nonstarchy vegetables and low in high-calorie foods such as sugared drinks.
The HEAL Study is a National Cancer Institute initiative designed to examine the links between diet, physical activity, body fat and breast-cancer prognosis. Patients enrolled in HEAL — including those participating in the study reported here — were diagnosed or treated at the Hutchinson Center, the University of New Mexico or the University of Southern California.
Between 1995 and 1998, the researchers followed 689 women enrolled in the HEAL program who were diagnosed with breast cancer, but who did not have type 2 diabetes. They monitored their health at periodic intervals beginning six months after diagnosis until September 2004 or the patient's death. From each patient, they collected a fasting blood sample — a common technique for measuring a baseline of insulin or C-peptide levels — and information on prognostic, demographic, and lifestyle factors, including weight and height.
To determine the relationship between C-peptide levels and prognosis, the researchers statistically adjusted the data they collected for confounding variables such as body-mass index, age, race, disease stage and therapy used in treatment. They found that, when arranged into three groups based on C-peptide levels, women in the top third of the group (highest levels) had twice the risk of death compared to women in the bottom third. When looking at just women with invasive breast cancer, the risk of death among women with high C-peptide levels was three times higher than among women with low C-peptide levels. The findings show that C-peptide and most likely insulin, in and of itself, is a marker for breast-cancer prognosis, according to McTiernan and colleagues.
[Adapted from materials provided by the American Association for Cancer Research.]
A clinical trial led by Dr. Anne McTiernan offers an opportunity for breast-cancer survivors to learn yoga while helping researchers study yoga's potential to treat cancer-related fatigue and weight gain and improve quality of life.
Recruiters for the Effect of Yoga on Weight, Quality of Life and Fatigue in Breast Cancer Patients Study seek 60 local, overweight female breast-cancer survivors (ages 21-75 years) who completed their primary treatment at least three months ago and do not currently practice yoga.
To learn more, call the Yoga Study information line at (206) 667-6818, e-mail firstname.lastname@example.org.