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Insulin Resistance Linked to Increased Breast Cancer Risk

Insulin Resistance Linked to Increased Breast Cancer Risk

SAN FRANCISCO—Insulin resistance, as determined by C-peptide levels,
appears to be linked to increased breast cancer risk, Celia Byrne, PhD, said at
the 93rd Annual Meeting of the American Association for Cancer Research
(abstract 1179). In a study of 1,226 women, those who developed breast cancer
were more likely than controls to have elevated concentrations of C-peptide,
considered an indication of insulin secretion.

"Women with the highest levels of C-peptide (in the highest quintile)
had a risk of breast cancer that was 68% greater than that of women with the
lowest levels of C-peptide (in the lowest quintile)," said Dr. Byrne,
instructor in medicine, Harvard Medical School and the Channing Laboratory of
Brigham and Women’s Hospital, Boston.

Nurses Health Study

Dr. Byrne and her colleagues at Harvard and McGill University identified 463
women diagnosed with breast cancer and 763 controls, matched for age,
menopausal status, time of blood collection, and fasting status, from the
32,826 participants in the Nurses Health Study.

All of the women were between 43 and 69 years of age when they gave a blood
sample in 1989 or 1990. The breast cancer cases were diagnosed within a 5-year
period following the collection of blood samples.

C-peptide levels increased with age, body mass index, and postmenopausal
status, and decreased with greater alcohol intake and physical activity. The
increased risk of breast cancer associated with elevated C-peptide levels
appeared somewhat stronger among women who were premenopausal when they gave
the blood sample, Dr. Byrne said.

"In general, C-peptide levels increased slightly with age, and they
increased quite dramatically with a higher body mass index," Dr Byrne
said. "Women who were physically active tended to have lower levels of
C-peptide, which may add to the evidence that physical activity lowers breast
cancer risk."


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