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Breast Cancer Risk and Hormone Receptor Status in Older Women by Parity, Age of First Birth, and Breastfeeding: A Case-Control Study
Ist Teil von
Cancer epidemiology, biomarkers & prevention, 2008-07, Vol.17 (7), p.1723-1730
Ort / Verlag
Philadelphia, PA: American Association for Cancer Research
Erscheinungsjahr
2008
Quelle
MEDLINE
Beschreibungen/Notizen
Background: Early age at first birth and multiparity reduce the risk of estrogen receptor-progesterone receptor (ERPR)–positive
breast cancer, whereas breastfeeding reduces the risk of both ERPR-positive and ERPR-negative cancers.
Methods: We used multivariable logistic regression analysis to investigate whether age at first birth (<25 or ≥25 years) and
breastfeeding (ever/never) modify the long-term effect of parity on risk of ERPR-positive and ERPR-negative cancer using 1,457
incident breast cancer cases and 1,455 controls ages ≥55 years who participated in the Women's Contraceptive and Reproductive
Experiences Study.
Results: Women who gave birth before age 25 years had a 36% reduced risk of breast cancer compared with nulligravida that
was not observed for women who started their families at an older age ( P heterogeneity = 0.0007). This protective effect was restricted to ERPR-positive breast cancer ( P heterogeneity = 0.004). Late age at first birth increased the risk of ERPR-negative cancers.
Additional births reduced the risk of ERPR-positive cancers among women with an early first birth ( P trend = 0.0001) and among women who breastfed ( P trend = 0.004) but not among older mothers or those who never breastfed. In women with a late first birth who never breastfed,
multiparity was associated with increased risk of breast cancer.
Conclusions: These findings suggest that the effect of parity on a woman's long-term risk of breast cancer is modified by
age at first full-term pregnancy and possibly by breastfeeding. (Cancer Epidemiol Biomarkers Prev 2008;17(7):1723–30)