Among the 7874 postmenopausal women, 2122 (55.8%) of 3803 case women and 2263 (55.6%) of 4071 control women overall reported that they had been breast-fed in infancy (Table 3).After adjusting for breast cancer risk factors, we found no evidence of a relationship between having been breast-fed as an infant and breast cancer occurrence in postmenopausal women (OR = 0.95; 95% CI = 0.85-1.07) (Table 3).
For comparability, control women were assigned a reference date that corresponded to the frequency of dates of diagnosis among case women within 5-year age strata (on average, about 1 year prior to interview).Although studies have shown that certain strains of mice transmit mammary tumor virus via breast milk, few epidemiologic studies have addressed this topic in humans.We evaluated the relationship between having been breast-fed as an infant and breast cancer risk among 8299 women who participated in a population-based, case-control study of breast cancer in women aged 50 years or more.ORs for the interaction between exposure to breast milk and mother's breast cancer status were similarly adjusted, but family history of breast cancer was excluded from this model because of its strong correlation with mother's breast cancer status.We conducted separate analyses for the 7874 postmenopausal women (3803 case women; 4071 control women) and for the 425 premenopausal women (205 case women; 220 control women).[J Nall Cancer Inst 1998;90: 921-4] Initial interest in a possible viral etiology for human breast cancer was generated by studies showing that mammary cancer in certain strains of mice can be caused by a tumor virus transmitted via breast milk () speculated that viral transmission through breast-feeding might also account for the elevated risk observed among women whose mothers had developed breast cancer.Although comprising small numbers of case women, their hospital-based studies provided no evidence of an association.The analyses are based on 8299 women (4008 case women; 4291 control women) who had an opportunity to answer this question.We used logistic regression models to evaluate having been breast-fed, maternal history of breast cancer, and the interaction between these two factors in relation to breast cancer occurrence.We evaluated the relationship between exposure to breast milk in infancy and breast cancer risk in a large populationbased, case-control study of women aged 50 years and over, who were born during a time period (1911 through 1945) when breast-feeding was relatively common (). population-based, case-control study of breast cancer. We identified case women through population-based cancer registries covering the states of Massachusetts, New Hampshire, and Wisconsin.We specifically addressed the hypothesis that an agent might be transmitted via breast milk, by evaluating whether breast cancer risk was increased among women who were breast-fed by a mother who subsequently developed breast cancer. Potentially eligible case women were of ages 50–79 years and were diagnosed with a first invasive breast cancer.