Fasting C-peptide levels and death resulting from all causes and breast cancer: the health, eating, activity, and lifestyle study.
OBJECTIVE
To examine the association between serum C-peptide, a marker of insulin secretion, measured 3 years after a breast cancer diagnosis, and death resulting from all causes and breast cancer.


METHODS
This was a prospective, observational study of 604 women enrolled onto the Health, Eating, Activity, and Lifestyle (HEAL) Study who were diagnosed with local or regional breast cancer between 1995 and 1998 and observed until death or December 31, 2006, whichever came first. The hazard ratio (HR) for all deaths and deaths owing to breast cancer and 95% CIs for the HR were estimated using multivariable stratified Cox regression analyses.


RESULTS
Among women without type 2 diabetes, fasting C-peptide levels were associated with an increased risk of death resulting from all causes and from breast cancer. A 1-ng/mL increase in C-peptide was associated with a 31% increased risk of any death (HR = 1.31; 95% CI, 1.06 to 1.63; P = .013) and a 35% increased risk of death as a result of breast cancer (HR = 1.35; 95% CI, 1.02 to 1.87, P = .048). Associations between C-peptide levels and death as a result of breast cancer were stronger in certain subgroups, including women with type 2 diabetes, women with a body mass index less than 25 kg/m(2), women diagnosed with a higher stage of disease, and women whose tumors were estrogen receptor positive.


CONCLUSIONS
Treatment strategies to reduce C-peptide levels in patients with breast cancer, including dietary-induced weight loss, physical activity, and/or use of insulin-lowering medications, should be explored.
Yale School of Public Health, P.O. Box 208034, New Haven, CT 06520-8034, USA. melinda.irwin@yale.edu
Melinda L
ML
Irwin
Catherine
C
Duggan
Ching-Yun
CY
Wang
Ashley Wilder
AW
Smith
Anne
A
McTiernan
Richard N
RN
Baumgartner
Kathy B
KB
Baumgartner
Leslie
L
Bernstein
Rachel
R
Ballard-Barbash
D001943:Breast Neoplasms / Q000097:blood* / Q000401:mortality* / Q000473:pathology; D002096:C-Peptide / Q000097:blood*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000209:etiology / Q000473:pathology; D005215:Fasting / Q000097:blood; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism; D007333:Insulin Resistance / Q000502:physiology; D000078790:Insulin Secretion; D008019:Life Style; D008875:Middle Aged; D009043:Motor Activity; D011379:Prognosis; D011446:Prospective Studies; D012307:Risk Factors
D002096:C-Peptide; D007328:Insulin