According to the results of a study presented at the 2007 annual meeting of the American Association for Cancer Research (AACR), breastfeeding may lessen the increased risk of breast cancer that comes from having a late age at first birth.
Breast cancer is diagnosed in over 200,000 women annually in the United States alone. Due to its prevalence, researchers have focused on evaluating environmental factors with potential links to the risk of breast cancer. Factors such as diet, exercise, age at menarche (first menstrual period), age at first childbirth, and breastfeeding appear to influence the likelihood of breast cancer. The effects of these factors on breast cancer risk, however, may be different for estrogen receptor-positive (ER-positive) and estrogen receptor-negative (ER-negative) breast cancers.
To evaluate the relationships among several reproductive factors and ER-positive and ER-negative breast cancer, researchers conducted a study among 995 women with breast cancer and 1,498 women without breast cancer. All women were age 55 or older.
- An early age at first birth (first birth before the age of 25) reduced the risk of ER-positive breast cancer but did not reduce the risk of ER-negative breast cancer.
- Breastfeeding reduced the risk of both ER-positive and ER-negative breast cancer. Importantly, breastfeeding appeared to reduce the increased risk of breast cancer experienced by women who had a later age at first birth (first birth after the age of 25).
In a prepared statement, Dr. Giske Ursin, one of the study authors, noted, “We suspect that women can reduce the increased risk that comes with later childbearing by choosing to breastfeed.”
Reference: Lord SJ, Bernstein L, Johnson K et al. Parity, breastfeeding and breast cancer risk by hormone receptor status in women with late age at first birth-a case-control study. Presented at the 2007 meeting of the American Association for Cancer Research, Los Angeles, CA, April 14-18, 2007. Abstract 2610.