Late age at first full term birth is strongly associated with lobular breast cancer

Abstract

BACKGROUND: Late age at first full-term birth and nulliparity are known to increase breast cancer risk. The frequency of these risk factors has increased in recent decades. METHODS: The purpose of this population-based casecontrol study was to examine associations between parity, age at first birth (AFB), and specific histological subtypes of breast cancer. Women with breast cancer were identified from cancer registries in Wisconsin, Massachusetts, and New Hampshire. Control subjects were randomly selected from population lists. Interviews collected information on reproductive histories and other risk factors. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) of ductal, lobular, and mixed ductal-lobular breast cancer diagnosis in association with AFB and nulliparity. RESULTS: AFB 30 years was associated with a 2.4-fold increase in risk of lobular breast cancer compared with AFB <20 years (OR, 2.4; 95% CI, 1.9-2.9). The association was less pronounced for ductal breast cancer (OR, 1.3; 95% CI, 1.2-1.4). Nulliparity was associated with increased risk for all breast cancer subtypes, compared with women with AFB <20 years, but the association was stronger for lobular (OR, 1.7; 95% CI, 1.3-2.2) than for ductal (OR, 1.2; 95% CI, 1.1-1.3) subtypes (P ¼ .004). The adverse effects of later AFB was stronger with obesity (P ¼ .03) in lobular, but not ductal, breast cancer. CONCLUSIONS: Stronger associations observed for late AFB and nulliparity suggest that these factors preferentially stimulate growth of lobular breast carcinomas. Recent temporal changes in reproductive patterns and rates of obesity may impact the histological presentation of breast cancer. Cancer 2011;117:1946-56.

Emerging Trends in Family History of Breast Cancer and Associated Risk

“…The CBCS is a population based case-control study that was carried out in Wisconsin, Massachusetts (apart from metropolitan Boston), Maine and New Hampshire (16–18). Eligible case subjects were women identified by each state’s cancer registry with a new breast cancer diagnosis.…”

Reproductive history and breast cancer risk

“…A meta-analysis of 9 cohort or case–control studies also revealed a reduced risk among patients with hormone receptor-positive cancers [17]. This protective effect was also observed in lobular carcinomas that are often positive for hormone receptors [25]. In this context, the relative protective effect of young age of first full-term birth has been observed mainly for postmenopausal women [17, 23, 24, 26].…”

Circulatory Estrogen Level Protects Against Breast Cancer in Obese Women

“…Nulliparity may be associated with ovulatory disorders in the majority of cases and there are studies, which equivocally exhibited increased prevalence of breast cancer in nulliparous women [161, 162]. Furthermore, coexistence of nulliparity and overweight may amplify each other’s effect on increasing breast cancer risk having strong synergism [161].…”