Red Meat and Breast Cancer

November 16, 2006 — Red meat intake increases the risk for hormone receptor–positive breast cancer in premenopausal women, according to the results of a prospective study reported in the November 13 issue of the Archives of Internal Medicine.

"The association between red meat intake and breast cancer is unclear, but most studies have assessed diet in midlife or later," write Eunyoung Cho, ScD, of the Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School in Boston, Massachusetts, and colleagues. "Although breast tumors differ clinically and biologically by hormone receptor status, few epidemiologic studies of diet have made this distinction."

In the Nurses' Health Study II, red meat intake and breast cancer risk were evaluated among premenopausal women aged 26 to 46 years. A food frequency questionnaire was administered in 1991, 1995, and 1999, and follow-up through 2003 determined self-reported breast cancers, which were confirmed by review of pathologic reports.

During 12 years of follow-up of 90,659 premenopausal women, 1021 cases of invasive breast carcinoma were documented. Greater intake of red meat was significantly associated with increased risk for estrogen- and progesterone-receptor–positive (ER+/PR+) breast cancers (n = 512), but not of estrogen- and progesterone-receptor–negative (ER-/PR-) cancers (n = 167).

Compared with women eating 3 or fewer servings per week of red meat, women eating more servings of red meat had higher multivariate relative risks for ER+/PR+ breast cancer. Relative risks were 1.14 (95% confidence interval [CI], 0.90 - 1.45) for more than 3 to 5 or fewer servings per week, 1.42 (95% CI, 1.06 - 1.90) for more than 5 servings per week to 1 or fewer servings per day, 1.20 (95% CI, 0.89 - 1.63) for more than 1 to 1.5 or fewer servings per day, and 1.97 (95% CI, 1.35 - 2.88) for more than 1.5 servings per day (P =.001 for trend).

For ER-/PR- breast cancer, the corresponding relative risks were 1.34 (95% CI, 0.89 - 2.00), 1.21 (95% CI, 0.73 - 2.00), 0.69 (95% CI, 0.39 - 1.23), and 0.89 (95% CI, 0.43 - 1.84), respectively (P for trend = .28). Higher intakes of several individual red meats were also strongly associated with elevated risk for ER+/PR+ breast cancer.

"Higher red meat intake may be a risk factor for ER+/PR+ breast cancer among premenopausal women," the authors write. "Because hormonal risk factors are more strongly related to hormone receptor–positive cancers, meat intake may operate through hormonal pathways.... Cooked or processed red meat is a source of carcinogens, such as heterocyclic amines, N-nitroso-compounds, and polycyclic aromatic hydrocarbons, that increase mammary tumors in animals and have been hypothesized to increase breast cancer risk."

Study limitations include lack of data on methods of preparation of red meat and possible errors in dietary assessment.

"Given that most of the risk factors for breast cancer are not easily modifiable, these findings have potential public health implications in preventing breast cancer and should be evaluated further," the authors conclude.

The National Institutes of Health supported this study. The authors have disclosed no relevant financial relationships.

Arch Intern Med. 2006;166:2253-2259.