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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 case-control 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 = .004). The adverse effects of later AFB was stronger with obesity (P = .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.
Copyright © 2010 American Cancer Society.
Inverse associations have been reported between birthweight and subsequent mortality from circulatory disease and diabetes among women. In the current study, we assessed whether perinatal factors were associated with mortality from breast cancer. This follow-up study consists of breast cancer cases who participated in two population-based case-control studies of breast cancer in women under age 45 years conducted between 1983 and 1992 in three western Washington counties. This analysis is restricted to the 1,024 cases or their proxies who completed a supplementary questionnaire on perinatal factors from 1994 to 1996. The mean and median length of follow-up among living cohort members were 153 and 148 months, respectively. Relative to women who were firstborn, women who were born second or higher in the birth order seemed to have lower mortality from breast cancer [hazard ratio (HR), 0.2; 95% confidence interval (95% CI), 0.2-0.3]. In contrast, maternal age of > or =35 years (HR, 1.7; 95% CI, 1.1-2.8) was associated with higher breast cancer mortality relative to a maternal age of <25 years. Birth order modified the effect of maternal age on mortality from breast cancer (P = 0.03). There was evidence of increased breast cancer mortality for birthweight of > or =4,000 g (HR, 1.8; 95% CI, 1.0-3.1) and twin membership (HR, 2.5; 95% CI, 1.0-6.2). The protective effect of being born second or higher in the birth order against breast cancer mortality regardless of maternal age is striking and needs to be confirmed in future studies.
PURPOSE - Specific events in the mother's reproductive history and certain birth characteristics have been associated with childhood leukemia. Few studies have explored these associations specifically in infants.
METHODS - The Children's Cancer Group (CCG) conducted three separate case-control studies of childhood leukemia that involved similar methodologies and data collection. Data from interviews of the mothers of a total of 303 children diagnosed with leukemia at 1 year of age or younger and their matched controls (n = 468) were available from the three studies. These data included maternal reproductive history (stillbirths, abortions, and miscarriages) and certain birth characteristics of the index child.
RESULTS - Compared with controls, cases were significantly more likely to be female (P < 0.01) and were more often heavier at birth (particularly cases diagnosed after 6 months of age (odds ratio, 4.18; 95% confidence interval, 1.75-10.02)). Overall, there were no statistically significant differences between cases and controls in regard to maternal report of any type of previous fetal loss. Finally, being a later-born child was associated with an increased risk of acute myeloid leukemia but not of acute lymphoblastic leukemia.
CONCLUSIONS - The relationships among birthweight, prior fetal loss, and risk of infant leukemia appear to be complex. Further studies of infant leukemia that incorporate molecular as well as epidemiologic data may help to elucidate these differences.
A high level of endogenous estrogen in utero has been hypothesized to be a possible risk factor for breast cancer. We used information from two population-based case-control studies to investigate the relation between perinatal factors and risk of invasive breast cancer among women age 21-45 years (746 cases, 960 controls) and women age 50-64 years (401 cases, 439 controls). Breast cancer cases were ascertained through a population-based cancer registry, and controls were selected by random digit dialing. After adjustment for age, menopausal status, and maternal smoking, the birthweight-breast cancer association in women age 21-45 years followed a J-shaped curve, with women whose birthweight was less than 2,500 gm [odds ratio (OR) = 1.3; 95% confidence interval (CI) = 0.9-2.0] and 4,000 gm or more (OR = 1.7; 95% CI = 1.1-2.5) at increased risk. Women age 50-64 years who were 4,000 gm or more at birth appeared to be at slightly reduced risk of breast cancer (OR = 0.6; 95% CI = 0.3-1.1). With the exception of maternal smoking, there was little effect of other perinatal factors on breast cancer risk in either group. These results support the hypothesized association between intrauterine estrogen exposure and subsequent risk of breast cancer.