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Objective: To investigate the relationship between allergy and risk of breast cancer in women 45 years of age and younger. Methods: Data were analyzed from a population-based case–control study of breast cancer in western Washington. Cases were women born after 1944 who were diagnosed with invasive breast cancer (n = 747) between January 1983 and April 1990. Controls (n = 958) were similarly aged women ascertained through random-digit dialing. Cases and controls were interviewed about their history of doctor diagnosed allergies, including detailed information on the specific types of allergies and the age of onset. Using logistic regression we examined the associations between allergy history and breast cancer. Results: A history of allergies was associated with a reduced risk of breast cancer for women older than 35 (odds ratio (OR) = 0.77; 95% confidence interval (CI) = 0.60–0.99), but not for women 35 years or younger (OR = 1.30; 95% CI = 0.94–1.81). There was little difference in effect when age of first allergy onset was examined. No specific type of allergy was associated with breast cancer risk. Conclusion: Our results provide some evidence that a history of allergy may be associated with a reduced risk of breast cancer for women who develop breast cancer between 35 and 45 years of age. Future studies are needed to verify the relationship between immune responses and breast cancer risk.

Objective: Postmenopausal hormone use and risk of breast cancer by histopathology was examined in a large multi-centered population-based case–control study. Methods: Women younger than 75 years newly diagnosed with invasive breast cancer between 1988 and 1991 were identified from statewide tumour registries in Wisconsin, Massachusetts, New Hampshire, and Maine. Only postmenopausal women were included in this analysis. Breast cancer cases (lobular (n = 219), ductal, NOS (n = 2172), and specific ductal subtypes (n = 242)) were compared with randomly selected population controls (n = 3179) using adjusted multi-variable polytomous logistic regression to estimate odds ratios (OR) and 95% confidence intervals (95%CI) for each histology. Results: Lobular carcinoma was associated with recent (within 2 years) estrogen therapy (OR:1.8, 95%CI: 1.0–3.4) and recent use of combined estrogen-plus-progestin therapy (OR:3.6, 95%CI: 1.8–7.6). Risk of ductal carcinoma was not associated with recent use of either estrogen alone (OR: 0.9, 95%CI: 0.7–1.2) or combined therapy (OR:0.9, 95%CI: 0.6–1.3). No associations were found with ductal subtypes. Conclusions: The association between postmenopausal hormone use and risk of breast cancer may depend on histopathology. Of particular interest is the association between combined hormone therapy and increased risk of lobular carcinoma. This lesion is increasingly common but, nonetheless, comprises fewer than 10% of invasive breast cancers.

Objective: To assess risk factors for breast cancer among very young compared to older premenopausal women. Methods: Between 1990 and 1992 a population-based case–control study conducted in Atlanta, GA, Seattle/Puget Sound, WA, and central NJ interviewed 3307 premenopausal women aged 20–54 years. Logistic regression models estimated adjusted relative risks (RR) and 95% confidence intervals (CI) for each of three 10-year age groups. Results: Among the youngest age group (

Objective: To examine the relation between breast cancer risk and job history among women 20–44 years of age who participated in a multi-center, population-based, case–control study. Methods: Participants consisted of women newly diagnosed with breast cancer (1642) and controls identified by random-digit dialing (1494). Details about the three longest jobs were collected and coded by an industrial hygienist. Odds ratios and 95% confidence intervals were calculated and adjusted for age, study site, and other breast cancer risk factors. Results: Several occupational and industrial categories were found to influence breast cancer risk. Stratification of the study population by parity revealed differences in breast cancer risk between the two groups for several occupational categories, including teachers, librarians or counselors (increased risk only among parous women) and natural scientists and mathematicians (decreased risk only among nulliparous women). Conclusions: This is among the first population-based case–control studies to examine occupational history and breast cancer risk in young women, with the ability to consider a wide array of potential confounders, including reproductive characteristics. This study provides further evidence of an increased breast cancer risk for several occupations and industries. Other findings were not as strongly supported by previous investigations.

Objectives: To evaluate the associations of dietary macronutrients, food groups, and eating patterns with risk of breast cancer in a population-based case–control study. Methods: In this study among women 20–44 years of age, 568 cases with breast cancer and 1451 population-based controls were included. They completed a detailed in-person interview, a self-administered food-frequency questionnaire and were measured for anthropometric indices. Logistic regression was used to estimate odds ratios (OR) and their 95% confidence intervals (CI) of breast cancer, adjusted for age, study site, race, education, alcohol consumption, oral contraceptive usage, smoking status, and body mass index. Results: There was no association between breast cancer risk and intake of calories, macronutrients, or types of fat. Risk of breast cancer was unrelated to intakes of a variety of food groups, including red meats, dairy, high-fat snacks and desserts, or foods high in animal fat. Increased risk was observed for high intake of a food group composed of sweet items, particularly sodas and desserts. Risk increased linearly with percent of calories from sweets and frequency of sweets intake. Consumption of sweets 9.8 or more times per week compared with

Objective: Exercise has been hypothesized to influence cancer risk through a variety of mechanisms including hormonal, metabolic and immunologic effects, yet its relation with the risk of thyroid cancer has not been examined. We conducted a population-based case–control study in women aged 18–64 in three counties of western Washington State to assess the relation of recreational physical activity with risk of papillary thyroid cancer. Methods: Of 558 women with thyroid cancer of the follicular epithelium diagnosed during 1988–1994 who were identified as eligible, 468 (83.9%) were interviewed; this analysis was restricted to women with papillary histology (n = 410). Controls (n = 574) were identified by random digit dialing, with a response proportion of 73.6%. Logistic regression was used to calculate odds ratios (OR) and associated confidence intervals (CI) estimating the relative risk of papillary thyroid cancer associated with various aspects of recreational exercise. Results: Risk of thyroid cancer was reduced among women who reported that they engaged in regular recreational exercise during the 2 years before diagnosis relative to women who did not report exercise during that time period (OR = 0.76, 95% CI 0.59–0.98). A similar risk reduction was noted among women who reported having exercised regularly between ages 12 and 21 (OR = 0.83, 95% CI 0.64–1.1). However, no clear associations with aspects of recreational activity, including average hours exercised per week or weekly energy expenditure, were observed. Conclusions: These results provide some initial support for the hypothesis that physical activity may reduce risk of thyroid cancer.

Background:Breast and thyroid cancer have been observed to occur more frequently than expected as multiple primary tumors in women. The study presented herein focuses on the effects of age at diagnosis and treatment for the first cancer on the development of the second cancer. Methods:This retrospective cohort study used a study population consisting of 38,632 women diagnosed with primary invasive breast cancer and 2189 women diagnosed with primary invasive thyroid cancer between 1974 and 1994. Cases were identified from records of the Cancer Surveillance System of western Washington and followed for subsequent cancer development through 1995. Results:Seventy-one women were diagnosed during their lives with both breast and thyroid cancers. Including cancers diagnosed during the same month as or after the initial cancer, the relative risk (RR) of breast cancer among women with thyroid cancer was 1.5 (95% confidence interval [CI] 1.1–2.0), and the RR of thyroid cancer among women with breast cancer was 1.5 (95% CI 1.1–2.2). Among women with thyroid cancer, risk of breast cancer was greatest when the latter cancer was diagnosed under 45 years of age (RR = 2.3, 95% CI 1.1–4.4). First course of treatment, including radiation or hormonal therapy to treat thyroid cancer, and radiation, chemotherapy, or hormonal therapy to treat breast cancer, did not alter a woman's risk of developing the second cancer. Conclusions:The data suggest that the incidence of breast and thyroid cancer may be related, and that in particular women with thyroid cancer may be at a moderately increased risk of developing breast cancer before age 45.

Objectives: The reported mutagenic and carcinogenic effects of some chemicals present in hair dyes have raised concern that hair dye use could increase breast cancer risk. This case–control study evaluated how detailed aspects of hair coloring and hair spray application by reproductive-age women may affect breast cancer risk. Methods: Cases were white female residents of three counties of western Washington state 45 years of age or less, who were diagnosed with breast cancer between 1983 and 1990 (n = 844). A sample of similarly aged women residing in the same counties served as controls (n = 960). Information on hair coloring and hair spray use, as well as other exposures, was ascertained during in-person interviews. Results: Breast cancer cases were slightly more likely than controls to report ever having used some type of hair coloring application, including use of rinses, semi-permanent or permanent dyes, as well as bleaching then dyeing or frosting their hair (relative risk [RR] = 1.3, 95% CI = 1.0–1.6, adjusted for age, fullterm pregnancies, family history of breast cancer, and weight). In subgroup analyses, women with exclusive use of just one of these methods of hair coloring application had no elevation in risk (similarly adjusted RR = 1.1, 95% CI = 0.9–1.3), whereas women who used two or more of these methods did have an elevated risk (RR = 1.9, 95% CI = 1.4–2.5). Hair spray use was not related to the risk of breast cancer (ever versus never users: RR = 1.0, 95% CI = 0.8–1.3). Conclusion: The lack of an association between exclusive use of a single type of hair coloring application and breast cancer risk argues that hair coloring application does not influence breast cancer risk among reproductive-age women. Thus, the results of the present study, as well as negative ones from most (but not all) prior studies, are most consistent with the conclusion that neither hair coloring application nor hair spray application influences breast cancer risk.

It has been hypothesized that women who participate in vigorous physical activity may have lower risk of breast cancer due to lower lifetime exposure to ovarian hormones. A population-based case-control study was conducted to investigate the association between leisure-time physical activity and risk of breast cancer among women aged 21 to 45 years. Cases were 747 women diagnosed with invasive breast cancer between 1983 and 1990 in three counties of western Washington state (United States), and were identified through the Seattle-Puget Sound Surveillance, Epidemiology, and End Results (SEER) registry. Controls were 961 women selected from the same area by random-digit telephone dialing. Physical activity was assessed through personal interview, with questions on frequency and duration of each type of recreational activity during the two-year period immediately prior to reference date (date of diagnosis for cases and a comparable assigned date for controls) and between ages 12 and 21. For the two-year time period before diagnosis, there was no association with frequency of activity (age-adjusted odds ratio [OR]=0.93, 95 percent confidence interval [CI]=0.71-1.22 for four or more episodes per week cf none), total hours spent in physical activity (age-adjusted OR=0.92, CI=0.71-1.22 for four or more hours per week cf none) or MET (metabolic equivalent energy expenditure unit) (age-adjusted OR=0.95, CI=0.73-1.23 for 18 or more METs per week cf none), nor any trend in risk with increasing activity levels. Similarly, there was no association between leisure activity during adolescence and breast cancer risk. These results were not confounded further by body mass index (wt/ht2), age at menarche, age at first full-term pregnancy, parity, family history of breast cancer, or other measured health behaviors. Our findings do not support a protective effect of leisure-time physical activity either in the adolescent years or in adulthood on breast cancer in young women.

To evaluate predictors of contralateral breast cancer risk, we examined data from a nested case-control study of second primary cancers among a cohort of women in western Washington (United States) diagnosed with breast cancer during 1978 through 1990 and identified through a population-based cancer registry. Cases included all women in the cohort who subsequently developed contralateral breast cancer at least six months after the initial diagnosis, but prior to 1992 (n = 234). Controls were sampled randomly from the cohort, matched to cases on age, stage, and year of initial breast cancer diagnosis. Information on potential risk factors for second primary cancer was obtained through medical record abstractions and physician questionnaires. Women who were postmenopausal due to a bilateral oophorectomy (i.e., a surgical menopause) at initial breast cancer diagnosis had a reduction in contralateral breast cancer risk compared with premenopausal women (matched odds ratio [mOR] = 0.25, 95 percent confidence interval [CI] = 0.09-0.68), whereas no reduction in risk was noted among postmenopausal women who had had a natural menopause (mOR = 0.90, CI = 0.39-2.09). Among postmenopausal women, there was a suggestion of a lower risk associated with relatively high parity (2+). A family history of breast cancer was associated with an increased risk (mOR = 1.96, CI = 1.22-5.15) and varied little by menopausal status. Having an initial tumor with a lobular component (c.f. a ductal histology) was not related strongly to risk (mOR = 1.47, CI = 0.79-2.74). The results of the present and earlier studies argue that we have limited ability to predict the occurrence of a contralateral breast tumor. Better predictors will be required before diagnostic and preventive interventions can be targeted to subgroups of patients with unilateral breast cancer.