CORRESPONDENCE

RESPONSE: Re: Plasma Folate, Vitamin B6, Vitamin B12, Homocysteine, and Risk of Breast Cancer

Shumin M. Zhang, Walter C. Willett, Jacob Selhub, David J. Hunter, Edward L. Giovannucci, Michelle D. Holmes, Graham A. Colditz, Susan E. Hankinson

Affiliations of Authors: S. M. Zhang, Department of Epidemiology, Harvard School of Public Health, and Division of Preventive Medicine and Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA; W.C. Willett, D. J. Hunter, E. L. Giovannucci, Departments of Nutrition and Epidemiology, Harvard School of Public Health, and Channing Laboratory, Brigham and Women’s Hospital and Harvard Medical School; J. Selhub, Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston; M. D. Holmes, Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School; G. A. Colditz, S. E. Hankinson, Department of Epidemiology, Harvard School of Public Health, and Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston.

Correspondence to: Shumin M. Zhang, M.D., Sc.D., Department of Nutrition, Harvard School of Public Health, 665 Huntington Ave., Boston, MA 02115 (e-mail: shumin.zhang{at}channing.harvard.edu).

The authors thank Schroecksnadel et al. for their interesting comments in regard to the suggested role for homocysteine as a potential tumor marker among cancer patients. They suggest that this observation seems to contradict the results from our study (1) that showed no association between plasma homocysteine and breast cancer risk. However, our study did not specifically address the role of homocysteine as a tumor marker because the blood samples that we analyzed were drawn (on average) several years before diagnosis of breast cancer among women (1). Our study was designed to investigate whether prediagnostic plasma homocysteine status predicts the future risk of breast cancer. However, we did not observe a statistically significant association between plasma homocysteine and breast cancer risk at either the first 2 years of follow-up (multivariable relative risk [RR] = 1.18, 95% confidence interval [CI] = 0.49 to 2.88, for highest versus lowest quintile; unpublished data) or at the last 4 years of follow-up (multivariable RR = 0.85, 95% CI = 0.54 to 1.35, for highest versus lowest quintile) (1). Thus, if homocysteine is a tumor marker, our data would suggest that it does not appear early in the disease process.

REFERENCES

1 Zhang SM, Willett WC, Selhub J, Hunter DJ, Giovannucci EL, Holmes MD, et al. Plasma folate, vitamin B6, vitamin B12, homocysteine, and risk of breast cancer. J Natl Cancer Inst 2003; 95:373–80.[Abstract/Free Full Text]



             
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