Keeping insulin in check important in breast cancer

By Megan Rauscher

NEW YORK (Reuters Health) - Women with breast cancer and elevated insulin levels face a significantly higher risk of death than their counterparts with lower insulin levels, research suggests.

Study investigator Dr. Melinda L. Irwin, from Yale University's School of Public Health, New Haven, Connecticut, urges breast cancer survivors to talk to their doctor about how to lower their insulin levels. "Breast cancer patients should take proven steps to lower their blood insulin levels, including exercise and eating a diet rich in fruits and vegetables and low in fat," she said.

The findings of the study were reported at the American Association for Cancer Research's Sixth International Conference on Frontiers in Cancer Prevention in Philadelphia.

Insulin is known to stimulate the growth of breast cancer cells in the laboratory, but few studies have examined the link between insulin levels and breast cancer prognosis.

To investigate, Irwin and colleagues examined data 689 for women who were enrolled in the Health, Eating, Activity and Lifestyle (HEAL) study at the time they were diagnosed with breast cancer. None of the women had diabetes at the outset. At study enrollment and over several years or until death, researchers analyzed blood levels of C-peptide -- a marker of how much insulin the body is producing.

They found that women with the highest C-peptide levels at the time of breast cancer diagnosis had almost twice the risk of death compared to women with lower C-peptide levels.

For women with invasive breast cancer -- meaning the cancer has spread throughout the breast tissue or to surrounding tissues -- the risk of death was three times higher in those with high C-peptide levels compared with women with low C-peptide levels.

The risk of death associated with higher C-peptide levels was particularly high among women in their 40s. "The higher death rate among younger women suggests that these women may have had more aggressive tumors, possibly related to tumor genetics or family history, Irwin noted in a statement.

"Our findings clearly show that C-peptide and most likely insulin, in and of itself, is a marker for breast cancer prognosis," she added.

Dr. Craig B. Thompson, director of the Abramson Cancer Center at the University of Pennsylvania, who moderated a press conference that detailed the study results, said the study illustrates the importance of controlling insulin levels in women with breast cancer.