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Estimating age-specific breast cancer risks: A descriptive tool to identify age interactions

Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institute of Health, Executive Plaza South 8070, 6120 Executive Plaza Blvd, Rockville, MD 20892-7242, USA.
Cancer Causes and Control (Impact Factor: 2.96). 06/2007; 18(4):439-47. DOI: 10.1007/s10552-006-0092-9
Source: PubMed

ABSTRACT Clarifying age-specific female breast cancer risks and interactions may provide important etiologic clues.
Using a population-based case-control study in Poland (2000-2003) of 2,386 incident breast cancer cases and 2,502 control subjects aged 25-74 years, we estimated age-specific breast cancer incidence rates according to risk factors.
Breast cancer risks were elevated among women with positive family history (FH), younger age at menarche, older age at first full-term birth, nulliparity, exogenous hormonal usage, and reduced physical activity (PA). Notwithstanding overall risks, we observed statistically significant quantitative (non-crossover) and qualitative (crossover) age interactions for all risk factors except for FH and PA. For example, nulliparity compared to parity reduced breast cancer risk among women ages 25-39 years then rates crossed or reversed, after which nulliparity increased relative risks among women ages 40-74 years.
Though quantitative age interactions could be expected, qualitative interactions were somewhat counterintuitive. If confirmed in other populations, qualitative interactions for a continuous covariate such as age will be difficult to reconcile in a sequential (multistep or monolithic) 'stochastic' breast cancer model. Alternatively, the reversal of relative risks among younger and older women suggests subgroup heterogeneity with different etiologic mechanisms for early-onset and late-onset breast cancer types.

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    • "A lot of studies about the association with etiology and risk factors of breast cancer were conducted, particularly physiological and reproductive factors. Various physiological and reproductive factors, including age at menarche, age at menopause, age at first pregnancy and parity have been shown to modify the risk of breast cancer (Oran et al, 2004; Anderson et al, 2007; Iwasaki et al, 2007). Our results in this study also demonstrated that early age at menarche (≤13 years old), later age at menopause (>50 years old) and later age at first pregnancy were associated with an increased risk for breast cancer, and childbirth was associated with a decreased risk for breast cancer. "
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