Cadmium exposure and breast cancer risk

Cadmium, a highly persistent heavy metal, has been categorized as a probable human carcinogen by the U.S. Environmental Protection Agency. Primary exposure sources include food and tobacco smoke. We carried out a population-based case-control study of 246 women, aged 20-69 years, with breast cancer and 254 age-matched control subjects. We measured cadmium levels in urine samples by inductively coupled plasma mass spectrometry and conducted interviews by telephone to obtain information on known breast cancer risk factors. Odds ratios (ORs) and 95% confidence intervals (CIs) for breast cancer by creatinine-adjusted cadmium levels were calculated by multivariable analysis. Statistical tests were two-sided. Women in the highest quartile of creatinine-adjusted cadmium level (> or = 0.58 microg/g) had twice the breast cancer risk of those in the lowest quartile (<0.26 microg/g; OR = 2.29, 95% CI = 1.3 to 4.2) after adjustment for established risk factors, and there was a statistically significant increase in risk with increasing cadmium level (P(trend) = .01). Based on this study, the absolute risk difference is 45 (95% CI = 0 to 77) per 100,000 given an overall breast cancer rate of 124 per 100,000. Whether increased cadmium is a causal factor for breast cancer or reflects the effects of treatment or disease remains to be determined.     

Circulating Sex Hormones and Mammographic Breast Density among Postmenopausal Women

The use of breast density as an intermediate or predictive marker of breast cancer risk is limited by an incomplete understanding of the etiology of breast density. High blood levels of endogenous estrogens and androgens are associated with increased risk of breast cancer among postmenopausal women. We sought to examine whether these hormones are also associated with breast density. The Wisconsin Breast Density Study enrolled 257 postmenopausal women, ages 55-70 years, with no history of postmenopausal hormone use, from mammography clinics in Madison, Wisconsin. Subjects provided a blood sample for sex hormone analysis, and breast density was measured from subjects' screening mammograms using a computer-assisted thresholding method. Numerous sex hormones were associated with breast density in age-adjusted analyses. However, further adjustment for body mass index and other potentially confounding factors substantially attenuated or eliminated these associations. In the fully adjusted model, there remained a positive association between percent breast density and serum progesterone (P=0.03), with percent density rising from 11.9% (95% CI: 9.8, 14.1%) among women in the lowest quartile of serum progesterone to 15.4% (12.9, 18.2%) among women in the highest quartile. There was also a positive association between sex hormone binding globulin and percent breast density (P=0.06). In contrast, there were no independent associations between percent breast density and estradiol (total, free, or bioavailable), estrone, estrone sulfate, or testosterone (total, free, or bioavailable). These results suggest that breast density has a hormonal etiology; however, it may differ in important ways from that of breast cancer risk.     

Urinary cadmium and serum levels of estrogens and androgens in postmenopausal Japanese women.

BACKGROUND: Recent laboratory studies have suggested that cadmium is an estrogenic compound and may be a potential risk factor for breast cancer. METHODS: We investigated the relationship between urinary cadmium concentrations and serum concentrations of estrone, testosterone, and dehydroepiandrosterone sulfate in 164 postmenopausal Japanese women. RESULTS: There was a significant positive association between the urinary cadmium and serum testosterone levels after controlling for age and body mass index. The mean testosterone level was 28% higher in women with high urinary cadmium (> or = 3.00 microg/g creatinine) than in those with low urinary cadmium (< 2.00 microg/g creatinine). Urinary cadmium was not significantly associated with serum estrone and dehydroepiandrosterone sulfate levels. Additional adjustment for smoking, alcohol and reproductive factors including known risk factors for breast cancer did not substantially alter the results. CONCLUSION: Data suggested that cadmium exposure is associated with increased testosterone levels. As high testosterone levels have been associated with the risk of breast cancer, the involvement of cadmium exposure in breast cancer risk should be evaluated in future studies.     

Blood arsenic levels and the risk of familial breast cancer in Poland

Arsenic is recognized as a potent carcinogen at high concentrations, but the relationship between environmental arsenic and breast cancer risk has not well been studied. Most research has focused on the effect of arsenic in populations with high endemic exposure, and not in populations with arsenic levels within normal limits. We sought to determine if blood arsenic levels predict the risk of breast and other cancers risk among women in northern Poland. The cohort consisted of 1,702 healthy women, aged 40 and above, identified between 2010 and 2017. Blood arsenic level was determined by inductively coupled plasma mass spectrometry. After an average of 4.5 years of follow-up (range 0.7–7.3 years), there were 110 incident cases of cancer diagnosed in the cohort, including 68 cases of breast cancer. Women in the highest quartile of arsenic had a highly significant 13-fold increased risk of developing breast cancer, compared to women in the lowest quartile (hazard ratio [HR] = 13.2; 95% confidence interval [CI] 4.02–43.0). Results were similar for arsenic and all incident cancers (HR quartile 4 vs. quartile 1 = 13.3; 95% CI 4.78–37.0). If confirmed, our study suggests that the blood arsenic level may be a useful predictive marker of cancer risk in women.     

Carbohydrates and the risk of breast cancer among Mexican women.

OBJECTIVE: High carbohydrate intake has been hypothesized to be a risk factor for breast cancer, possibly mediated by elevated levels of free insulin, estrogens, and insulin-like growth factor-1. Therefore, we conducted a population-based case-control study among a Mexican population characterized by relatively low fat and high carbohydrate intakes. METHODS: Women ages 20 to 75 years, identified through six hospitals in Mexico City (n = 475), were interviewed to obtain data relating to diet (using a food frequency questionnaire) and breast cancer risk factors. Controls (n = 1,391) were selected from the Mexico City population using a national sampling frame. RESULTS: Carbohydrate intake was positively associated with breast cancer risk. Compared with women in the lowest quartile of total carbohydrate intake, the relative risk of breast cancer for women in the highest quartile was 2.22 [95% confidence interval (95% CI) 1.63-3.04], adjusting for total energy and potential confounding variables (P for trend < 0.0001). This association was present in premenopausal and postmenopausal women (for highest versus lowest quartile, odds ratio 2.31, 95% CI 1.36-3.91 in premenopausal women and odds ratio 2.22, 95% CI 1.49-3.30 in postmenopausal women). Among carbohydrate components, the strongest associations were observed for sucrose and fructose. No association was observed with total fat intake. DISCUSSION: In this population, a high percentage of calories from carbohydrate, but not from fat, was associated with increased breast cancer risk. This relation deserves to be investigated further, particularly in populations highly susceptible to insulin resistance.     

Phyto-oestrogen Intake and Breast Cancer Risk in South Asian Women in England: Findings from a Population-based Case-Control Study

OBJECTIVE: This study investigates whether intake of phyto-oestrogens is associated with breast cancer risk in South Asian women from the Indian subcontinent, whose diet is rich in pulses and vegetables but poor in soyfoods. METHODS: A total of 240 South Asian breast cancer cases living in England and 477 age-matched population-based controls were recruited into the study. Dietary intake was measured using a validated food frequency questionnaire. Conditional logistic regression models were used to estimate the effect of phyto-oestrogen intake on breast cancer risk. RESULTS: After adjustment for known breast cancer risk factors and total energy intake, there was moderate evidence of a dose-effect response in the odds of breast cancer with isoflavone intake (p-value for trend 0.08), with women in the top quartile having approximately half the odds of breast cancer of those in the bottom one (odds ratio (OR) 0.58, 95% confidence interval (CI) 0.33, 1.00) but with no reductions in the odds for women in the second and third quartiles. The ORs for second, third and highest quartiles of total lignan intake compared to the lowest were 0.78 (95% CI 0.48, 1.26), 0.74 (0.46, 1.19) and 0.66 (0.41, 1.07), respectively, again with moderate evidence of a linear dose-effect response (p-value for trend 0.09). Further adjustment for non-startch polysaccharides (NSP) intake slightly weakened the phyto-oestrogens-breast cancer associations. CONCLUSIONS: These findings are consistent with the possibility that high phyto-oestrogen intake may protect against breast cancer, but further research is required to confirm this hypothesis.     

Multiple diagnostic X-rays for spine deformities and risk of breast cancer.

BACKGROUND: Ionizing radiation is a well-established human mammary carcinogen. Women historically monitored by radiography at young ages for abnormal spinal curvature are an exposed population suitable for investigating radiation-related risk and its variation by modifying factors. In this historic cohort, 95% of daily dose increments (when exposure to the breast occurred) were under 2.4 cGy, with mean 1.1 cGy. METHODS: A retrospective cohort of 3,010 women, diagnosed with spinal curvature between 1912 and 1965 in 14 U.S. pediatric orthopedic centers and who completed a questionnaire by telephone interview or mail survey in 1992, were studied for risk of breast cancer by radiation dose to the breast (mean, 12 cGy) after adjustment for established breast cancer risk factors. RESULTS: A borderline-significant radiation dose response (excess relative risk/Gy = 2.86; P = 0.058; one-tailed P = 0.029) was observed during 118,905 woman-years of follow-up (median, 35.5 years) based on 78 cases of invasive breast cancer. The dose response was significantly greater (P = 0.03) for women who reported a family history of breast cancer in first- or second-degree relatives (excess relative risk/Gy = 8.37; 95% confidence interval, 1.50-28.16). Radiation-related risk did not vary significantly by stage of reproductive development at exposure. CONCLUSIONS: Assuming that repair of radiation-related DNA damage requires at most a few hours, our data argue against existence of a low-dose threshold on the order of 1 to 3 cGy for radiation exposure contributing to breast carcinogenesis. The possibility that a family history of breast cancer may have enhanced a carcinogenic radiation effect requires confirmation in other studies.     

中青年与老年非吸烟女性肺癌危险因素的比较研究

目的 分析比较中青年和老年非吸烟女性肺癌的危险因素。方法 于1992年2月～1993年12月，在上海市区完成了一项大规模全人群女性肺癌病例对照研究，共调查了非吸烟女性肺癌病例504例及人群对照601例。根据年龄把研究对象分为两组，35～54岁和55～69岁组，并分析比较两组的结果。单因素分析采用Mantel—Haenszel分层分析法，进一步调整混杂因素采用多变量logistic回归模型。结果分析结果显示，中青年组危险因素是做饭时眼和喉烟雾刺激感，最高一组比数比为3．40；其次是肺癌家族史，比数为5．80。而保护因素是饮茶(OR：0．40)和活产次数(5次及以上组OR：0．39)。老年组的危险因素主要是：高身体指数(最高一组OR：1．69)、工作场所被动吸烟史(OR：1.55)、厨房在卧室内(OR：1．50)、做饭时厨房内烟雾较多(OR：2．43)、菜油为主要食用油(OR：1.94)等。此外。肺结核病史和肺癌家族史可能增加老年女性患肺癌的危险性。保护因素是维生素C(最高一组OR：0．45)，趋势检验有统计学意义。中青年组和老年组肺癌的结果比较表明，无论是危险因素还是保护因素，两者都有不同。结论 中青年和老年非吸烟女性肺癌的病因可能存在一定的差异。     

Lifetime recreational and occupational physical activity and risk of in situ and invasive breast cancer.

Numerous studies have observed reduced breast cancer risk with increasing levels of physical activity, yet these findings have been inconsistent about optimal times of activity and effect modification by other factors. We investigated the association between recreational and occupational physical activity and breast cancer risk in a population-based case-control study in Massachusetts, New Hampshire, and Wisconsin. During structured telephone interviews, 7,630 controls, 1,689 in situ, and 6,391 invasive breast cancer cases, ages 20 to 69 years, reported lifetime history of recreational physical activity and occupation. Neither lifetime recreational nor strenuous occupational physical activity appeared to be associated with risk of breast carcinoma in situ. In contrast, recreational physical activity was associated with a reduced risk of invasive breast cancer. After adjustment for potentially confounding factors, women averaging >6 h per week of strenuous recreational activity over their lifetime had a 23% reduction in the odds ratio of invasive breast cancer when compared with women reporting no recreational activity (95% confidence interval, 0.65-0.92; P(trend) = 0.05). However, this reduction in risk was limited to women without a first-degree family history of breast cancer (P(interaction) = 0.02). Inverse associations were observed for physical activity early in life, in the postmenopausal years, and in the recent past, but these findings were confined to women without a family history of breast cancer. Lifetime strenuous occupational activity was not associated with invasive breast cancer risk. These results provide further evidence that, for most women, physical activity may reduce the risk of invasive breast cancer.     

Breast cancer risk in relation to amount of tissue removed during breast reduction operations in Sweden

BACKGROUND: Women who undergo breast reduction operations have substantially lowered risks of breast cancer, and the reasons remain unclear. The current investigation attempted to assess whether the reduction in breast cancer risk was related directly to the amount of breast tissue removed. METHODS: Medical record retrieval was attempted for 161 breast cancer patients in a Swedish cohort of 31,910 women who had had breast reduction surgery and for 483 women who had not developed breast cancer. Information on amount of breast tissue removed was abstracted along with other factors that influence breast cancer risk. Odds ratios of developing breast cancer were calculated based on amount of breast tissue removed. RESULTS: The amount of tissue removed was a significant predictor of risk, as subjects in the highest quartile of tissue removal had a significantly lower risk than those in the lowest quartile. Considering the total amount of tissue removed (both breasts), subjects with > or = 1600 versus < 800 grams removed had an odds ratio (OR) of 0.24 [95% confidence interval (CI) 0.1-0.5]. This relation persisted after adjustment for other breast cancer risk factors and was apparent within every subgroup examined. CONCLUSIONS: The finding that breast cancer risk was reduced in proportion to the amount of tissue removed should be reassuring to women who are considering breast reduction procedures and to women who are electing to have bilateral total prophylactic mastectomies because of a strong genetic predisposition.     

Urinary endogenous sex hormone levels and the risk of postmenopausal breast cancer

To assess the relation between urinary endogenous sex steroid levels and the risk of postmenopausal breast cancer, a nested case-cohort study was conducted within a large cohort (the DOM cohort) in the Netherlands (n=9,349). Until the end of follow-up (1 January 1996), 397 postmenopausal breast cancer cases were identified and a subcohort of 424 women was then taken from all eligible women. Women using hormones were excluded, leaving 364 breast cancer cases and 382 women in the subcohort for the analyses. Concentrations of oestrone, oestradiol, testosterone, 5alpha-androstane-3alpha, 17beta-diol and creatinine were measured in first morning urine samples, which had been stored since enrolment at -20 degrees C. A Cox proportional Hazards model was used, with Barlow's adjustment for case-cohort sampling, to estimate breast cancer risk in quartiles of each of the, creatinine corrected, hormone levels, the lowest quartile being the reference group. Women with higher levels of all four of the hormones were at increased risk for postmenopausal breast cancer (highest vs lowest quartile: incidence rate ratio for oestrone (IRR(oestrone)=2.5, 95% CI: 1.6-3.8; IRR(oestradiol)=1.5, 95% CI: 1.0-2.3; IRR(testosterone)=1.6, 95% CI: 1.0-2.4; IRR(5alpha-androstane-3alpha, 17beta-diol)=1.7, 95% CI: 1.1-2.7). In conclusion, women with higher excretion levels of both oestrogens and androgens have an increased risk of breast cancer.     

Statin use and risk of breast cancer

BACKGROUND: Findings that statins inhibited the proliferation of breast cancer cells in vitro and in rodents have raised interest in whether the use of statins might decrease a woman's risk of developing breast cancer. We analyzed data from a population-based case-control study to evaluate the association between the use of statins and breast cancer risk. METHODS: Cases of incident invasive breast cancer in women 50 years of age or older and diagnosed from 1995-2001 were identified from population-based cancer registries in Wisconsin, Massachusetts, and New Hampshire. Controls were randomly selected, within each state, from lists of licensed drivers and Medicare beneficiaries. Information on the use of statins and other breast cancer risk factors was ascertained from structured telephone interviews. RESULTS: Overall, breast cancer cases were not more likely than controls to have ever used statins. Ever use of lipophilic statins as a group (simvastatin, lovastatin, and fluvastatin) and ever use of the hydrophilic statin pravastatin were also not associated with breast cancer risk. Ever use of fluvastatin was associated with a decreased risk of breast cancer (odds ratio [OR], 0.5; 95% confidence interval, 0.3-0.8) but the magnitude of the ORs did not vary across categories of duration of use. CONCLUSIONS: The use of statins overall was not associated with breast cancer risk.     

Vitamin D and reduced risk of breast cancer: a population-based case-control study.

BACKGROUND: Vitamin D, antiproliferative and proapoptotic in breast cancer cell lines, can reduce the development of mammary tumors in carcinogen-exposed rats. Current evidence in humans is limited with some suggestion that vitamin D-related factors may reduce the risk of breast cancer. We conducted a population-based case-control study to assess the evidence for a relationship between sources of vitamin D and breast cancer risk. METHODS: Women with newly diagnosed invasive breast cancer were identified from the Ontario Cancer Registry. Women without breast cancer were identified through randomly selected residential telephone numbers. Telephone interviews were completed for 972 cases and 1,135 controls. Odds ratios (OR) and 95% confidence intervals (CI) for vitamin D-related variables were estimated using unconditional logistic regression with adjustment for potential confounders. RESULTS: Reduced breast cancer risks were associated with increasing sun exposure from ages 10 to 19 (e.g., OR, 0.65; 95% CI, 0.50-0.85 for the highest quartile of outdoor activities versus the lowest; P for trend = 0.0006). Reduced risk was also associated with cod liver oil use (OR, 0.76; 95% CI, 0.62-0.92) and increasing milk consumption (OR, 0.62 95% CI 0.45-0.86 for >or=10 glasses per week versus none; P for trend = 0.0004). There was weaker evidence for associations from ages 20 to 29 and no evidence for ages 45 to 54. CONCLUSION: We found strong evidence to support the hypothesis that vitamin D could help prevent breast cancer. However, our results suggest that exposure earlier in life, particularly during breast development, maybe most relevant. These results should be confirmed.     

Folate, vitamin B(6), and vitamin B(12) intake and the risk of breast cancer among Mexican women.

BACKGROUND: High intake of folate, vitamin B(6), and vitamin B(12) have been hypothesized to lower the risk for breast cancer. We conducted a population-based case-control study to evaluate the risk for breast cancer among Mexican women with relatively low vitamin intakes. METHODS: We included 475 women (median age, 53 years; range, 23-87 years) diagnosed with incident breast cancer through six hospitals in Mexico City and interviewed them to obtain data on breast cancer risk factors and their usual diet using a food frequency questionnaire. We selected 1,391 (median age, 49 years; range, 18-82 years) controls from the Mexico City population using a national sampling frame. RESULTS: Compared with women in the lowest quartile, the odds ratio for breast cancer for women in the highest quartile of folate intake was 0.64 [95% confidence intervals (CI), 0.45-0.90; P, test for trend = 0.009] and 0.32 (95% CI, 0.22-0.49; P, test for trend < 0.0001) for vitamin B(12) intake. Among postmenopausal women, intakes of folate and vitamin B(12) were associated with a lower risk of breast cancer and those associations were stronger than among premenopausal women. The inverse association of folate and breast cancer was stronger among women who consumed a high level of vitamin B(12) as compared with women consuming diets low in vitamin B(12). No association was observed for vitamin B(6) intake. CONCLUSIONS: In this population, high intakes of folate and vitamin B(12) were independently associated with decreased breast cancer risk, particularly among postmenopausal women.     

Urinary cadmium and mammographic density in premenopausal women

Mammographic density (MD), a strong marker of breast cancer risk, is influenced by genetic, environmental, and hormonal factors. Cadmium, a persistent and widespread environmental pollutant, has been associated with risk of breast cancer, and laboratory evidence suggests cadmium is a carcinogen in the breast. We investigated the hypothesis that cadmium exposure is associated with higher MD. In a cross-sectional study of MD and urinary cadmium concentration, percentage MD (MD%) and Breast Imaging-Reporting and Data Systems (BI-RADS?) density category were determined from screening mammograms of 190 premenopausal women ages 40–45 years. Women completed a health questionnaire, and the cadmium content of spot urine samples was measured with inductively coupled plasma mass spectrometry and corrected for urine creatinine. Urinary cadmium concentrations are thought to reflect exposure to cadmium during a period of 20–30 years. Multivariable linear regression and logistic regression were used to estimate the strength of association between urinary cadmium and mammographic breast density. Adjusted mean MD% among women in the upper tertile of creatinine-corrected urinary cadmium was 4.6% higher (95% CI: –2.3 to 11.6%) than in women in the lowest cadmium tertile. Each twofold increase in urinary cadmium was associated with higher odds of MD% in the upper tertile (OR: 1.29, 95% CI: 0.82–2.02) or a BI-RADS category rating of “extremely dense” (OR: 1.75, 95% CI: 1.14–2.70). Stronger associations were observed among nulliparous women, and current or former smokers. Exposure to cadmium may be associated with increased breast density in premenopausal women.     

Early-life physical activity and postmenopausal breast cancer: effect of body size and weight change.

It is not yet known whether early-life physical activity reduces the risk of developing breast cancer. Subgroup analyses according to menopausal status and body mass may help clarify this association. Data from a population-based case-control study of female residents of Wisconsin, Massachusetts, Maine, and New Hampshire were used to examine associations between body mass and breast cancer risk. Cases (n = 4614) were identified by each state's tumor registry; controls (n = 5817) were randomly selected from population lists. Frequency of participation in strenuous physical activity when 14-22 years of age, weight at age 18 and 5 years before interview, height, and other factors were ascertained through structured telephone interviews. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were computed using logistic regression. Reductions in postmenopausal breast cancer risk associated with strenuous physical activity were greatest for women in the fourth quartile of body mass index at age 18; the OR for women with the highest activity frequency on average (> or =once/day) was 0.45 (95% CI = 0.26-0.79). Associations with frequency of activity also varied by weight change. Compared to women with no activity and little adult weight gain, frequent physical activity was associated with reduced postmenopausal breast cancer risk in women who had lost weight since age 18 (OR = 0.19, 95% CI = 0.05-0.70) or had gained little or modest amounts of weight (weight gain: first tertile, OR = 0.36, 95% CI = 0.05-0.85; second tertile, OR = 0.31, 95% CI = 0.14-0.66). Weighted MET score analyses yielded similar but less inverse results. These findings suggest that the reduced risk of postmenopausal breast cancer associated with frequent, early-life physical activity may be greatest in women who, over the adult years, either lost weight or gained only modest amounts.     

Association between cadmium and breast cancer risk according to estrogen receptor and human epidermal growth factor receptor 2: epidemiological evidence

The study aimed to examine the association between cadmium (Cd) and the risk of breast cancer according to estrogen receptor (ER) and human epidermal growth factor receptor 2 (HER2). A hospital-based case–control study was carried out in 585 cases and 1,170 controls. Information on possible risk factors was collected via a structured questionnaire. Urinary Cd was determined by atomic absorption spectrometry. The ER and HER2 levels in tumor tissue were analyzed by immunohistochemistry. Logistic regression was used to calculate odds ratios (ORs) and 95 % confidence intervals (CIs) for breast cancer by creatinine-adjusted urinary Cd. Women with greater creatinine-adjusted urine Cd (3rd quartile: 0.241–0.399 μg/g and 4th quartile: ≥0.4 μg/g) experienced 1.6 times higher risk of breast cancer compared with those having Cd concentration lower than 0.147 μg/g (1st quartile) [OR = 1.6, (95 % CI 1.19, 2.17) and OR = 1.62 (95 % CI 1.19, 2.21), respectively, P trend = 0.001] after adjustment for age and other confounders. Both ER+ and HER2? cases from the highest quartile of urine Cd exhibited approximately twice the breast cancer risk of those in the lowest quartile [OR = 1.9, (95 % CI 1.31, 2.74) and OR = 1.87, (95 % CI 1.33, 2.62), respectively, P trend <0.001) after adjustment for confounders. The data support cadmium as a risk factor for breast cancer, especially for both ER+ and HER2? cancer patients.     

Adipocytokine resistin and breast cancer risk

Adipocytokine resistin is a member of the newly discovered family of cysteine-rich protein. Recent data suggest that macrophages are a major source of human resistin. Given the obesity-breast cancer link and convergence of adipocyte and macrophage function, resistin may provide unique insight into links between obesity, inflammation, and breast cancer risk in humans. We conducted a hospital-based case–control study to evaluate whether plasma resistin levels were associated with breast cancer risk in women. We also examined the modification effect of estrogen exposures on the resistin–breast cancer link. Questionnaire information, anthropometric measures, and blood samples were taken before treatment from 380 incident cases with breast cancer and 760 controls admitted for health examination at the Tri-Service General Hospital, Taipei between 2004 and 2008. Plasma levels of resistin were measured by enzyme immunoassay. Cumulative exposure to estrogens were estimated according to the age at menarche and age at enrollment for premenopausal women and age at menarche and age at menopause for postmenopausal women. Cases with breast cancer had significantly elevated resistin concentrations as compared with control subjects. Compared with those in the lowest quartile, the adjusted odds ratios of breast cancer for women in the second, third, and highest quartiles were 1.48 [95% confidence interval (CI) = 0.65–3.38], 1.76 (95% CI = 1.00–4.73), and 2.08 (95% CI = 1.04–3.85), respectively. Furthermore, the biological gradient of breast cancer risk by plasma resistin levels remained after adjustment for measurers of adiposity. The dose-dependent relationship of resistin levels with breast cancer risk was notably pronounced among women with excess exposure to estrogens. Adipocytokine resistin may have an adiposity-independent role in breast carcinogenesis. Mechanistic studies to fully elucidate the mechanisms underlying resistin’s effects should be pursued in future investigations.     

Prospective study of height, body mass index and risk of breast cancer.

The associations of breast cancer risk with height and body mass index have been examined in 291 cases of breast cancer that occurred among 25,967 Norwegian women during a mean follow-up of approximately 14 years (range 12-16 years). There was an overall increased risk of breast cancer with increasing body height, and the relative risk of women in the fourth quartile of height (mean = 170 cm) was 1.43 (95% confidence limits, 1.18-1.73) compared to women in the lowest quartile (mean = 155 cm), after adjusting for age, parity, age at first birth, and county of residence. Simultaneously, there was an overall inverse relation between body mass index (BMI) and breast cancer risk, which, however, was confined to women 50 years or younger. After adjustment for age, parity, age at first birth, and county of residence, the relative risk of women (less than or equal to 50 years) in the highest quartile of BMI (mean Quetelet = 30) was 0.63 (95% confidence limits, 0.48-0.82), compared to women in the lowest (mean Quetelet = 21). We propose that the lower breast cancer risk in shorter women may reflect caloric restriction during the pre- and peripubertal period, which may affect hyperplastic growth, and lead to a reduced number of breast tissue cells. The negative association with BMI may be related to a lower rate of cell division of breast tissue among obese premenopausal women.     

Chemical exposures in the workplace and breast cancer risk: A prospective cohort study

We investigated the relationship between workplace chemical exposures and breast cancer risk among women enrolled in the Sister Study, a prospective cohort study of US and Puerto Rican women. A total of 47,640 participants reported work outside of the home. Workplace exposure to eleven agents (acids, dyes or inks, gasoline or other petroleum products, glues or adhesives, lubricating oils, metals, paints, pesticides, soldering materials, solvents and stains or varnishes) was characterized based on self‐reports of frequency and duration of use. Approximately 14% of the study population reported exposure to only one agent and 11% reported working with two or more of the 11 agents in their lifetime. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated for each agent, adjusting for established breast cancer risk factors. During follow‐up, 1,966 cases of breast cancer were reported. Although there were no significant associations between ever use of the eleven agents evaluated and breast cancer risk, women with cumulative exposure to gasoline or petroleum products at or above the highest quartile cutoff had an elevated risk of total (HR: 2.3, 95%CI: 1.1–4.9) and invasive (HR: 2.5, 95%CI: 1.1–5.9) breast cancer compared with women in the lowest quartile group (p_trend = 0.03). Workplace exposure to soldering materials was associated with an increased risk of premenopausal breast cancer (HR = 1.8, 95% CI = 1.1–3.0). Findings support the need for further studies to elucidate the role of occupational chemicals in breast cancer etiology.