Pregnancy-related factors and the risk of breast carcinoma in situand invasive breast cancer among postmenopausal women in the California Teachers Study cohort

Abstract

IntroductionAlthough pregnancy-related factors such as nulliparity and late age at first full-term pregnancy are well-established risk factors for invasive breast cancer, the roles of these factors in the natural history of breast cancer development remain unclear.MethodsAmong 52,464 postmenopausal women participating in the California Teachers Study (CTS), 624 were diagnosed with breast carcinoma in situ (CIS) and 2,828 with invasive breast cancer between 1995 and 2007. Multivariable Cox proportional hazards regression methods were used to estimate relative risks associated with parity, age at first full-term pregnancy, breastfeeding, nausea or vomiting during pregnancy, and preeclampsia.ResultsCompared with never-pregnant women, an increasing number of full-term pregnancies was associated with greater risk reduction for both breast CIS and invasive breast cancer (both P trend < 0.01). Women having four or more full-term pregnancies had a 31% lower breast CIS risk (RR = 0.69, 95% CI = 0.51 to 0.93) and 18% lower invasive breast cancer risk (RR = 0.82, 95% CI = 0.72 to 0.94). Parous women whose first full-term pregnancy occurred at age 35 years or later had a 118% greater risk for breast CIS (RR = 2.18, 95% CI = 1.36 to 3.49) and 27% greater risk for invasive breast cancer (RR = 1.27, 95% CI = 0.99 to 1.65) than those whose first full-term pregnancy occurred before age 21 years. Furthermore, parity was negatively associated with the risk of estrogen receptor-positive (ER+) or ER+/progesterone receptor-positive (PR+) while age at first full-term pregnancy was positively associated with the risk of ER+ or ER+/PR+ invasive breast cancer. Neither of these factors was statistically significantly associated with the risk of ER-negative (ER-) or ER-/PR- invasive breast cancer, tests for heterogeneity between subtypes did not reach statistical significance. No clear associations were detected for other pregnancy-related factors.ConclusionsThese results provide some epidemiologic evidence that parity and age at first full-term pregnancy are involved in the development of breast cancer among postmenopausal women. The role of these factors in risk of in situ versus invasive, and hormone receptor-positive versus -negative breast cancer merits further exploration.

Breast-feeding and benign breast disease

“…Among women with invasive BC, higher parity and the absence or short duration of breast-feeding were independently associated with triple-negative BC (Shinde et al 2010). Th erefore, even if parity is a known protective factor against BC in general (Yang et al 2011;Ma et al 2010), it seems to play a role, as well as lactation, in triple-negative BC and BBD development. In our opinion, a better understanding of the infl uence of pregnancy on those pathologies could give us more information on their aetiologies.…”

“…It is known that breast-feeding and pregnancy are protective against malignant breast disease and are risk factors for BBD (Ma et al 2010;Minami et al 1998). In the literature, it is not clarifi ed if there is a correlation between breast-feeding and its duration with BBD.…”

Assessment of Midwifery Student Preparation for Performing the Role of Breast Cancer Educator

“…Woman's hormonal system exerts a notable effect on breast cancer, the course of treatment, and the results of some therapeutical methods. Therefore, hormone characteristics, as well as their impact on some physiological phenomena, such as menstruation, pregnancy or lactation become very important (Freund et al, 2005;Cummings et al, 2009;Ma et al, 2010;Faupel-Badger et al, 2013).…”

“…The research suggests the breast feeding to be one of the simplest and at the same time an effective way of protection against breast cancer; however, no sufficiently valid proof of a protective effect of this factor has been found so far (Collaborative Group on Hormonal Factors in Breast Cancer, 2002;Lodha et al, 2011;do Carmo França-Botelho et al, 2012;Faupel-Badger et al, 2013). In a way, breast feeding may protect against breast cancer; still pregnancy proved itself to have a notably more protective effect (Freund et al, 2005;Ma et al, 2010;Kobayashi et al, 2012). The majority of the questioned Poles (94.7%), and above two thirds of Belgian students (71.7%) considers breast feeding as a protective means against the development of breast cancer.…”

Prevention of Breast Cancer Could Be a Consequence of Pregnancy: A Review

“…Epidemiological, clinical and pathological studies have uncovered novel aspects regarding the complexity of this disease [7][8][9]. We know that age at diagnosis and ethnicity are associated with a specific tumor type and tumor behavior, which in turn are influenced by a woman's age at the first pregnancy [10,11].…”