Abstract
Several reproductive factors are known to be associated with risk of breast cancer; however, relationships between these factors with risk of second primary asynchronous contralateral breast cancer (CBC) have not been widely studied. The Women’s Environmental, Cancer, and Radiation Epidemiology (WECARE) Study is a population-based case-control study of 1521 CBC cases and 2212 individually matched controls with unilateral breast cancer. Using multivariable conditional logistic regression models, we examined associations between reproductive factors and CBC risk, and whether associations differed by estrogen receptor (ER) status and menopausal status of the first breast cancer. Older age at menarche was inversely associated with CBC risk (≥14 vs. ≤11 years risk ratio (RR) = 0.82, 95 % confidence interval (CI) 0.65–1.03, Ptrend = 0.02). Among parous women, an increasing number of full-term pregnancies (FTP) was inversely associated with risk (≥4 vs. 1 FTP RR = 0.60, 95 % CI 0.41–0.88, Ptrend = 0.005). Ever breast-feeding was inversely associated with CBC risk only among women with ER-negative first tumors (ever vs. never breast-fed RR = 0.69, 95 % CI 0.48–1.00, Pheterogeneity = 0.05). Older age at first FTP was inversely associated with CBC risk among women with ER-negative first tumors (≥30 vs. <20 years old RR = 0.66, 95 % CI 0.35–1.27, Ptrend = 0.03), but suggestively positively associated with risk among women with ER-positive first tumors (Pheterogeneity = 0.03). Young age at menarche and low parity, both risk factors for first primary breast cancer, were also associated with overall CBC risk. Reductions in risk associated with breast-feeding were limited to women with ER-negative first tumors, who are at higher CBC risk than women with ER-positive primaries.
Highlights
Reproductive factors, including menstrual and reproductive history, are well-established predictors of breast cancer risk
We examined whether associations between reproductive factors and contralateral breast cancer (CBC) risk differed according to estrogen receptor (ER) status of the first primary tumor, menopausal status at first diagnosis, and time since first diagnosis
Older age at menarche was associated with reduced risk only among women who were postmenopausal at first diagnosis (≥14 vs. ≤11 years risk ratios (RRs) = 0.45, 95 % confidence intervals (CIs) 0.25–0.81, Ptrend < 0.001, Pheterogeneity = 0.0001), with similar RR estimates irrespective of ER status (Table 4)
Summary
Reproductive factors, including menstrual and reproductive history, are well-established predictors of breast cancer risk. First and second primary breast tumors have been shown to share some risk factors, including mutations in BRCA1 and BRCA2 (Graeser et al 2009; Metcalfe et al 2004), family history of breast cancer (Bernstein et al 1992; Hemminki et al 2007), and obesity (Druesne-Pecollo et al 2012). Some prior studies have observed a reduced risk of CBC with parity (Bernstein et al 1992; Ricceri et al 2015; Storm et al 1992) and younger age at first birth (Vaittinen and Hemminki 2000), though others, potentially limited by small sample sizes, have reported null associations with these and other reproductive factors (Boice et al 1992; Cook et al 1996; Horn and Thompson 1988; Li et al 2003). No studies of CBC have investigated whether these associations are modified by estrogen receptor (ER) status
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
