Breast-feeding Reduces Risk for Basal-like Breast Cancer
Posted on May, 2008

Women with an early menarche, high adiposity, and multiple births who do not breast-feed face an increased risk for developing the basal subtype of breast cancer compared with other subtypes, a US study has found.

(Breast Cancer Research and Treatment, May, 2008)

In the Carolina Breast Cancer Study, risk factors for the newly identified “intrinsic” breast cancer subtypes: luminal A, luminal B, HER2-overexpressing, & basal-like, were determined. Immunohistochemical markers were used to subtype 1,424 cases of invasive & in situ breast cancer, and case subtypes were compared to 2,022controls.

The researchers found that:

• Luminal A, the most common subtype, exhibited risk factors typically reported for breast cancer in previous studies, including inverse associations for increased parity & younger age at first full-term pregnancy.
• Basal-like cases exhibited several associations that were opposite to those observed for luminal A, including increased risk for parity & younger age at first term full-term pregnancy.
• Longer duration breastfeeding, increased number of children breastfed, and increasing number of months breastfeeding per child were associated with reduced risk of basal-like breast cancer, but not luminal A.
• Women with multiple live births who did not breastfeed & women who used medications to suppress lactation were at increased risk of basal-like but not luminal A breast cancer.
• Elevated waist-hip ratio was associated with increased risk of luminal A in postmenopausal women, and increased risk of basal-like breast cancer in pre- & postmenopausal women.
• The prevalence of basal-like breast cancer was highest among premenopausal African-American women, who also showed the highest prevalence of basal-like risk factors.
• The researchers estimate that up to 68% of basal-like breast cancers in young African American women, and over half of cases in the general population, could be prevented by promoting breastfeeding & reducing abdominal adiposity.