Spontaneous abortion and risk of fatal breast cancer in a prospective cohort of United States women

Controversy exists over the possible relationship between induced and spontaneous abortion and risk of breast cancer. Thus, the association of fatal breast cancer and spontaneous abortion was examined in a large prospective study of United States adult women. After seven years of follow-up, 1,247 cases of fatal breast cancer were observed among 579,274 women who were cancer-free at interview in 1982 and who provided complete reproductive histories. Results from Cox proportional hazards models, adjusted for other risk factors, showed no association between a history of spontaneous abortion and risk of fatal breast cancer (rate ratio [RR]=0.89, 95 percent confidence interval [CI]=0.78–1.02). The RR did not increase with increasing numbers of abortions. Parous women who had a spontaneous abortion before their first term birth were not at increased risk compared with parous women with no history of spontaneous abortion (RR=0.76, CI=0.54–1.05). Women whose only pregnancy ended in a spontaneous abortion were not at increased risk compared with women who were never pregnant (RR=0.61, CI=0.27–1.38) or whose only pregnancy ended in a livebirth (RR=0.72, CI=0.32–1.65). These findings do not support an association between spontaneous abortion and fatal breast cancer.     

Breast cancer risk in relation to abortion: Results from the EPIC study

The role of spontaneous and induced abortion on breast cancer risk is examined among 267,361 women recruited into the European Prospective Investigation into Cancer and nutrition between 1992 and 2000. The data were collected from 20 centers, across 9 countries, and included information on a total of 4,805 women with breast cancer, of whom 1,657 reported having ever had any type of abortion. Overall, the relative risk of breast cancer in women who reported ever having had a spontaneous abortion was not significantly elevated when compared with women who reported never having had such an abortion (RR = 1.07, 95% CI = 0.99-1.14). However, there was some evidence of a slight increase in the risk of breast cancer among women who reported having had 2 or more spontaneous abortions (1.20, 1.07-1.35). The relative risk of breast cancer among women who reported ever having had an induced abortion when compared to women who reported never having had an induced abortion was 0.95 (0.87-1.03). Overall, the findings provide further unbiased evidence of the lack of an adverse effect of induced abortion on breast cancer risk.     

Spontaneous and induced abortions and risk of breast cancer.

The relationship between spontaneous or induced abortion and the risk of breast cancer was analyzed in a case-control study conducted in the greater Milan area on 2,394 cases of breast cancer and 2,218 controls in hospital for a spectrum of acute conditions, not gynecological, hormonal or neoplastic. No consistent relationship emerged between spontaneous or induced abortion and breast cancer: compared with women reporting no abortions (spontaneous or induced), the multivariate relative risk (RR) was 1.0 (95% confidence interval, CI, 0.9 to 1.2) in those reporting one abortion and 0.9 (95% CI 0.7 to 1.0) in those reporting two or more. This lack of association was consistent in strata of age and parity, including younger women. We further analyzed the risk of breast cancer associated with an abortion before and after full-term pregnancy. Compared with parous women reporting no induced or spontaneous abortions, those who had an abortion before their first full-term pregnancy had about a 20% higher risk of breast cancer. This finding, however, was not statistically significant (RR 1.2, 95% CI 0.9 to 1.7). No increased risk was observed in women who had had a first abortion after a full-term pregnancy (RR 0.9, 95% CI 0.8 to 1.0). This study does not support the hypothesis that spontaneous or induced abortion appreciably influences subsequent breast-cancer risk.     

Abortions and breast cancer risk in premenopausal and postmenopausal women in Jiangsu Province of China

To evaluate the relationship between abortions and risk of breast cancer, we conducted a case-control study with 669 cases and 682 population-based controls in Jiangsu Province of China. A structured questionnaire was used to elicit detailed information. Unconditional logistic regression analysis was performed to calculate odds ratios (ORs) and 95% confidence intervals (CIs). The results have revealed that induced abortion was related to increased risk of breast cancer. Premenopausal women who had ≥ 3 times of induced abortion were at increased crude OR (2.41, 95%CI: 1.09-5.42) and adjusted-OR (1.55, 95%CI: 1.15-5.68). Postmenopausal women with a previous induced abortion were at increased crude OR (2.04, 95%CI: 1.48-2.81) and adjusted-OR (1.82, 95%CI: 1.30-2.54), and there was a significant increase trend in OR with number of induced abortions (p for trend: 0.0001). Overall, spontaneous abortion did not significantly alter the risk of breast cancer, but postmenopausal women who had history of spontaneous abortion were at increased OR. These results suggested that relationship between breast cancer and abortions may depend on menopausal status and induced abortion may played an important role in the development of breast cancer in Jiangsu' women of China.     

Abortion history and breast cancer risk: results from the Shanghai Breast Cancer Study

Studies of the association between induced abortion and breast cancer risk have been inconsistent, perhaps due to underreporting of abortions. Induced abortion is a well-accepted family planning procedure in China, and women who have several induced abortions do not feel stigmatized. The authors used data from a population-based case-control study of breast cancer among women age 25-64 conducted between 1996 and 1998 in urban Shanghai to assess whether a history of and the number of induced abortions were related to breast cancer risk. In-person interviews were completed with 1,459 incident breast cancer cases ascertained through a population-based cancer registry, and 1,556 controls randomly selected from the general population in Shanghai (with respective response rates of 91% and 90%). After adjusting for confounding, there was no relation between ever having had an induced abortion and breast cancer (odds ratio [OR] = 0.9, 95% confidence interval [CI] 0.7-1.2). Women who had 3 or more induced abortions were not at increased risk of premenopausal breast cancer (OR = 0.9, 95% CI 0.6-1.4) or postmenopausal breast cancer (OR = 1.3, 95% CI 0.8-2.3). These results suggest that a history of several induced abortions has little influence on breast cancer risk in Chinese women.     

Induced and spontaneous abortion in relation to risk of breast cancer (United States)

The relation of induced and spontaneous abortion to the risk of breast cancer is evaluated in a hospital-based case-control interview study conducted in three cities in the United States from 1985 through 1995. Cases were 1,803 women aged 25 to 64 years with newly diagnosed invasive breast cancer; controls were 4,182 women of the same ages admitted for conditions unrelated to reproductive factors. Other breast cancer risk-factors were controlled through multiple logistic regression. The reference for allanalyses was women who had never had an abortion, either induced or spontaneous. Among parous women, the relative risk (RR) estimate was 1.1 (95percent confidence interval [CI] = 0.9-1.5) for induced abortion overall, 1.0(CI = 0.7-1.4) for abortion before the first birth, and 1.3 (CI = 1.0-1.8)for abortion after at least one birth. Among nulliparous women, the relative risk estimate for induced abortion was 1.3 (CI = 0.9-1.9). There was no trend of increased risk with number of abortions, nor was there consistent evidence of an increased risk in any particular subgroup. Spontaneous abortion was not associated with increased risk of breast cancer, either among nulliparous women or among parous women. These findings provide little support for the hypothesis that induced abortion increases breast cancer risk overall or in particular subgroups. This revised version was published online in July 2006 with corrections to the Cover Date.     

A prospective study of induced abortion and breast cancer in African-American women

OBJECTIVE: There continues to be controversy about whether induced abortion influences the risk of breast cancer. Because case-control studies of this relation are subject to recall bias, there is a need for prospective data. Further, there has been little study of abortion and breast cancer in African-American women. We assessed the relation of abortion to risk of breast cancer in a prospective follow-up study of African-American women. METHODS: Black Women's Health Study participants have been followed by mailed questionnaires every two years since enrollment in 1995. Participants reported 348 incident breast cancers during 205,983 person-years of follow-up. Women who had an induced abortion were compared with women who had never had one, with nulliparous and parous women analyzed separately. Incidence rate ratios (IRR) with two-sided 95% confidence intervals (CI) were derived from Cox regression models that controlled for age, age at first birth, number of births, history of spontaneous abortion, and other factors. RESULTS: Among nulliparous women, the IRR for any induced abortion relative to none was 0.9 (95% CI = 0.5-1.4), and among parous women, the comparable IRR was 1.1 (95% CI = 0.8-1.4). Risk did not vary by number of abortions, age at first abortion, age at diagnosis or a family history of breast cancer in either nulliparous or parous women. CONCLUSIONS: Our findings indicate that induced abortion does not increase breast cancer risk in African-American women.     

Circulating colony stimulating factor-1 and breast cancer risk

Colony stimulating factor-1 (CSF1) and its receptor (CSF1-R) are important in mammary gland development and have been implicated in breast carcinogenesis. In a nested case-control study in the Nurses' Heath Study of 726 breast cancer cases diagnosed between June 1, 1992, and June 1, 1998, and 734 matched controls, we prospectively evaluated whether circulating levels of CSF1 (assessed in 1989-1990) are associated with breast cancer risk. The association varied by menopausal status (P(heterogeneity) = 0.009). CSF1 levels in the highest quartile (versus lowest) were associated with an 85% reduced risk of premenopausal breast cancer [relative risk (RR), 0.15; 95% confidence interval (95% CI), 0.03-0.85; P(trend) = 0.02]. In contrast, CSF1 levels in the highest quartile conferred a 33% increased risk of postmenopausal breast cancer (RR, 1.33; 95% CI, 0.96-1.86; P(trend) = 0.11), with greatest risk for invasive (RR, 1.45; 95% CI, 1.02-2.07; P(trend) = 0.06) and ER+/PR+ tumors (RR, 1.72; 95% CI, 1.11-2.66; P(trend) = 0.04). Thus, the association of circulating CSF1 levels and breast cancer varies by menopausal status.     

Abortions and breast cancer: record-based case-control study

It has been suggested that abortions leave the breast epithelium in a proliferative state with an increased susceptibility to carcinogenesis. Results from previous studies of induced or spontaneous abortions and risk of subsequent breast cancer are contradictory, probably due to methodological considerations. We investigated the relationship between abortions and subsequent breast cancer risk in a case-control study using prospectively recorded exposure information. The study population comprised women recorded in the population-based Swedish Medical Birth Register between 1973-91. Cases were defined by linkage of the birth register to the Swedish Cancer Register and controls were randomly selected from the birth register. From the subjects' antenatal care records we abstracted prospectively collected information on induced and spontaneous abortions, as well as a number of potential confounding factors. Relative risk of breast cancer was estimated by odds ratios (OR) with 95% confidence intervals (95% CI). A reduced risk of breast cancer was observed for women with a history of at least 1 compared to no abortions (adjusted OR = 0.84, 95% CI = 0.72-0.99). The adjusted OR decreases step-wise with number of abortions to 0.59 (95% CI = 0.34-1.03) for 3 or more compared to no abortions. The patterns are similar for induced and spontaneous abortions. In conclusion, neither a history of induced nor spontaneous abortions is associated with an increased risk of breast cancer. Our data suggest a protective effect of pregnancies regardless of outcome.     

A record-based evaluation of induced abortion and breast cancer risk (United States)

Objective:Previous studies of induced abortion and breast cancer may have been limited by differential reporting of abortion history. We conducted a population-based case–control study to evaluate abortion (both induced and spontaneous) and breast cancer risk. Methods:All study subjects were aged 20–69 years and members of Group Health Cooperative of Puget Sound (GHC). Incident invasive breast cancer cases (n = 138) were identified from the linkage between the GHC enrollment file and the Seattle–Puget Sound SEER Cancer Registry. Controls (n = 252) were randomly selected from GHC enrollment files and matched to cases on age and enrollment period. All subjects had to have been enrolled at GHC for the 2 years preceding diagnosis (cases) or reference (controls) date. The unified medical record of each case was abstracted for pregnancy history, including prior induced and spontaneous abortions, menopause status, height and weight, screening practices, and other risk factors. Results:Compared to all women who had never had an induced abortion, the multivariate adjusted relative risk of breast cancer in women with an induced abortion was 0.9 (95% confidence interval 0.5–1.6). This risk was similar in parous women, and nulliparous women. There was no association between spontaneous abortion and breast cancer risk. Conclusions:These results do not support a relation between induced abortion and breast cancer incidence.     

A sequence repeat in the insulin-like growth factor-1 gene and risk of breast cancer

Insulin-like growth factor-1 (IGF-I), a potent mitogen, is hypothesized to influence breast cancer risk. In 3 previous studies, a polymorphism in the IGF-1 gene (sequence repeat length) was associated with plasma IGF-I level. We evaluated prospectively the relationships among a (CA)(n) repeat polymorphism in the IGF-1 gene, IGF-I level and breast cancer risk in a nested case-control study conducted within the Nurses' Health Study. Blood samples were collected in 1989-1990; up to June 1994, we identified 463 cases of breast cancer. One to 2 controls were selected per case, matched by age, menopausal status, postmenopausal hormone use, month and time of day of blood collection and fasting status, for a total of 622 controls. Although no significant trend was observed, plasma IGF-I levels were significantly lower among controls, with no copy of the 19 allele, compared with those homozygous for the 19 (CA)(n) repeat length (146 and 173 ng/ml, respectively; p-value for pairwise mean comparison = 0.005). In conditional logistic regression, controlling for established breast cancer risk factors, we observed no significant association between (CA)(n) repeat length genotype and risk of breast cancer [compared with repeat genotype 19/19-18/19 genotype relative risk (RR) = 0.96, 95% confidence interval (CI) = 0.56-1.64; 18/20 genotype RR = 0.92, 95% CI = 0.39-2.19; 19/20 genotype RR = 1.16, 95% CI = 0.82-1.64; 19/21 genotype RR = 0.69, 95% CI = 0.42-1.14; 20/20 genotype RR = 0.55, 95% CI = 0.28-1.10; 20/21 genotype RR = 0.72, 95% CI = 0.29-1.79]. Results did not vary substantially when evaluated according to menopausal status, tumor receptor status or category of other breast cancer risk factors. Although a modest association cannot be excluded, our data do not support an important relation between this IGF-1 gene polymorphism and breast cancer risk.     

Soy intake and breast cancer risk in Singapore Chinese Health Study

We investigated the effects of soy isoflavone intake on breast cancer in a prospective study of 35,303 Singapore Chinese women enrolled during April 1993 to December 1998 in the Singapore Chinese Health Study. At recruitment, each subject was personally administered a validated semiquantitative food frequency questionnaire covering 165 food and beverage items. As of December 31,2005, 629 had developed breast cancer following an accumulation of 338,242 person-years. Using Cox regression and adjusting for age at interview, year of interview, dialect group, education, family history of breast cancer, age when periods became regular, parity, menopausal status, body mass index (BMI), n-3 fatty acid, and other covariates, we found breast cancer risk was reduced significantly in association with high soy intake. Relative to women with lower (below median) soy intake (<10.6 mg isoflavone per 1000 Kcal), women with higher (above median) intake showed a significant 18% risk reduction (relative risk (RR)=0.82, 95% confidence interval (CI)=0.70-0.97). This inverse association was apparent mainly in postmenopausal women (RR=0.74, 95% CI=0.61-0.90), and was not observed in premenopausal women (RR=1.04, 95% CI=0.77-1. 40). Among postmenopausal women, the soy-breast cancer association was stronger in those above median BMI (RR=0.67, 95% CI=0.51-0.88) than in leaner women (RR=0.83, 95% CI=0.62-1.11). Duration of follow-up modified the soy-breast cancer association, the effect being twice as large among women with 10+ vs fewer years of follow-up. Neither oestrogen nor progesterone receptor status of the tumours materially influenced the association. These prospective findings suggest that approximately 10 mg of isoflavones per day, obtained in a standard serving of tofu, may have lasting beneficial effects against breast cancer development.     

Impact of menstrual and reproductive factors on breast cancer risk in Japan: results of the JACC study

The incidence of breast cancer among Japanese women, a traditionally low-risk population, has increased substantially. To evaluate the association of reproductive factors with breast cancer risk, we examined 38,159 Japanese women, aged 40-79 years, who responded to a questionnaire on reproductive and other lifestyle factors from 1988 to 1990 in the Japan Collaborative Cohort Study. During an average 7.6 years of follow-up, we documented 151 incidents of breast cancers. Cox proportional hazards modeling was employed to estimate relative risks (RR) and 95% confidence intervals (CI). There was a significant decline in the risk of breast cancer with increasing parity among parous women (trend P=0.01). Women with four or more parities had a 69% lower risk than uniparous women, a reduced risk was also evident among menopausal women. Breast cancer risk tended to rise with increasing age at first delivery (trend P=0.05), the association being very apparent among menopausal women (trend P=0.02). Compared to the women who had their first delivery before age 25, those who delayed this event until after age 34 had an RR of 2.12 (95% CI: 0.72-6.21) and 3.33 (1.07-10.3) among the overall subjects and the menopausal, respectively. There was no apparent association of breast cancer risk with age at menarche or menopause. Our study concerning reproductive risk factors suggests that breast cancer in Japan is similar to that in Western countries, and that reproductive factors, particularly the number of parity and age at first delivery, might be important in the etiology of breast cancer among Japanese women.     

Body weight at age 20 years, subsequent weight change and breast cancer risk defined by estrogen and progesterone receptor status--the Japan public health center-based prospective study

Few prospective studies have investigated the association between BMI at age 20 years (BMI20y) and breast cancer risk with consideration to estrogen/progesterone receptor status (ER/PR). We evaluated the association between BMI20y and ER/PR-defined breast cancer risk among 41,594 women in the population-based Japan Public Health Center-based Prospective Study. Anthropometric factors were assessed using self-reported questionnaires. Relative risks (RRs) were estimated by Cox proportional hazards regression models. Through to the end of 2006, 452 breast cancer cases were identified. We observed a statistically significant inverse association between BMI20y and breast cancer incidence [multivariable-adjusted RR for each 5-unit increment 0.75 (95%CI=0.61-0.92)], which was not modified by menopausal or recent BMI status. In contrast, recent BMI and subsequent BMI gain were not associated with increased risk among premenopausal women, but were substantially associated with increased risk among postmenopausal women [corresponding RR(recent BMI)=1.31 (95%CI=1.07-1.59); RR(subsequent BMI gain)=1.32 (95%CI=1.09-1.60)]. In subanalyses by receptor status (～50% of cases), the observed inverse association of BMI20y with risk was consistent with the result for ER-PR- [0.49 (95%CI=0.27-0.88)], while the observed positive associations of BMI gain with postmenopausal breast cancer risk appeared to be confined to ER+PR+ tumors [corresponding RR(for subsequent BMI gain)=2.24 (95%CI=1.50-3.34)]. Low BMI at age 20 years was substantially associated with an increased risk of breast cancer. In contrast, high recent BMI and subsequent BMI gain from age 20 were associated with increased risk of postmenopausal ER+PR+ tumors.     

Differential effects of reproductive factors on the risk of pre- and postmenopausal breast cancer. Results from a large cohort of French women

The aim of this study was to obtain a better understanding of the role of hormonal factors in breast cancer risk and to determine whether the effect of reproductive events differs according to age at diagnosis. It analysed the effect of age at menarche, age at first full-term pregnancy, number of full-term pregnancies and number of spontaneous abortions both on the overall risk of breast cancer and on its pre- or postmenopausal onset, using the data on 1718 breast cancer cases, obtained from a large sample of around 100000 French women participating in the E3N cohort study. The results provide further evidence that the overall risk of breast cancer increases with decreasing age at menarche, increasing age at first pregnancy and low parity. No overall effect of spontaneous abortions was observed. The effect of these reproductive factors differed according to menopausal status. Age at menarche had an effect on premenopausal breast cancer risk, with a decrease in risk with increasing age of 7% per year (P<0.05). Compared to those who had their first menstrual periods at 11 or before, women experiencing menarche at 15 or after had an RR of 0.66 (95% CI 0.45-0.97) in the premenopausal group. Age at first full-term pregnancy had an effect on both pre- and postmenopausal breast cancer risk, with significant tests showing increasing risk per year of increasing age (P=0.001 and P<0.05 respectively). A first full-term pregnancy above age 30 conveyed a risk of 1.63 (95% CI 1.12-2.38) and 1.35 (95% CI 1.02-1.78) in the pre- and postmenopausal groups respectively. A protective effect of high parity was observed only for postmenopausal breast cancer risk (P for trend test =0.001), with point estimates of 0.79 (95% CI 0.60-1.04), 0.69 (95% CI 0.54-0.88), 0.66 (95% CI 0.51-0.85) and 0.64 (95% CI 0.48-0.86) associated to a one, two, three and four or more full-term pregnancies. A history of spontaneous abortion had no significant effect on the risk of breast cancer diagnosed before or after menopause. Our results suggest that reproductive events have complex effects on the risk of breast cancer.     

Epidemiology of reproductive and hormonal factors in thyroid cancer: evidence from a case-control study in the Middle East.

Thyroid cancer is the second most common neoplasm among women in Kuwait and several other countries in the Middle East. Most of these countries also have relatively high birth and total fertility rates. To examine potential relationships between reproductive and hormonal factors and thyroid cancer, we conducted a population-based case-control interview study among 238 women diagnosed with thyroid cancer and a similar number of individually matched controls in Kuwait. Among the demographic variables, women with 12+ years of education had a significantly reduced risk of thyroid cancer (OR = 0.4; 95% CI: 0.2-0.8; p-trend <0.05). The average age at diagnosis (+/-SD) of thyroid cancer was 34.7 +/- 11 years. Events such as age at menarche, pregnancy, menopausal status and age at menopause were not associated with thyroid cancer. There was an association with age at last pregnancy and parity. Women who had their last pregnancy at ages > or = 30 years were at a significantly increased risk (OR = 2.1; 95% CI: 1.2-3.8); there was also a significant trend in risk with increasing age at last pregnancy. There was a modest increase in risk among women who had borne > or = 5 children (OR = 1.5; 95% CI: 0.9-2.5). A joint analysis of these factors showed that childbearing during the latter half of reproductive life had a substantial effect on the incidence of thyroid cancer; for any given level of parity, there was about a 2-fold increased risk if the age at last pregnancy was > or = 30 years. A substantial recent-birth effect, in relation to subsequent diagnosis of thyroid cancer, was observed during the second and third year after a birth (OR = 2.0; 95% CI: 1.0-4.1). In contrast, spontaneous abortion seemed to have a protective effect. There was a significant decrease in risk among women who had a miscarriage as outcome of first pregnancy (OR = 0.1; 95% CI: 0.03-0.4) and those who had experienced > or = 3 miscarriages (OR = 0.3; 95% CI: 0.1-0.8; p-trend <0.05). Overall, any female hormone use was not associated with thyroid cancer risk. New association is suggested for a history of post-partum thyroiditis (OR = 10.2; 95% CI: 2.3-44.8). These data support the hypothesis that reproductive factors and patterns may influence, or contribute to, the risk of thyroid cancer among women.     

Body weight and incidence of breast cancer defined by estrogen and progesterone receptor status--a meta-analysis

Epidemiological evidence indicates that the association between body weight and breast cancer risk may differ across menopausal status as well as the estrogen receptor (ER) and progesterone receptor (PR) tumor status. To date, no meta-analysis has been conducted to assess the association between body weight and ER/PR defined breast cancer risk, taking into account menopausal status and study design. We searched MEDLINE for relevant studies published from January 1, 1970 through December 31, 2007. Summarized risk estimates with 95% confidence intervals (CIs) were calculated using a random-effects model. The summarized results of 9 cohorts and 22 case-control studies comparing the highest versus the reference categories of relative body weight showed that the risk for ER+PR+ tumors was 20% lower (95% CI=-30% to -8%) among premenopausal (2,643 cases) and 82% higher (95% CI=55-114%) among postmenopausal (5,469 cases) women. The dose-response meta-analysis of ER+PR+ tumors showed that each 5-unit increase in body mass index (BMI, kg/m2) was associated with a 33% increased risk among postmenopausal women (95% CI=20-48%) and 10% decreased risk among premenopausal women (95% CI=-18% to -1%). No associations were observed for ER-PR- or ER+PR- tumors. For discordant tumors ER+PR- (pre) and ER-PR+ (pre/post) the number of cases were too small (<200) to interpret results. The relation between body weight and breast cancer risk is critically dependent on the tumor's ER/PR status and the woman's menopausal status. Body weight control is the effective strategy for preventing ER+PR+ tumors after menopause.     

Circulating levels of insulin-like growth factors, their binding proteins, and breast cancer risk.

BACKGROUND: Earlier data support the hypothesis that the relation between circulating insulin-like growth factor-I (IGF-I) levels and breast cancer risk differs by menopausal status. The strong association of IGF-I with height in childhood and weak or no association between adult levels and adult height also suggest that IGF levels in young women may better reflect an exposure time period of importance to breast cancer. Few studies have assessed IGF binding protein-1 (IGFBP-1) or free IGF and breast cancer risk. MATERIALS AND METHODS: We conducted a large case-control study nested within the prospective Nurses' Health Study. Plasma concentrations of IGF-I, free IGF, IGFBP-3, and IGFBP-1 were measured in blood samples collected in 1989 to 1990. Eight hundred women were identified who had a diagnosis of invasive or in situ breast cancer after blood collection, up to 1998, 27% of whom were premenopausal at blood collection. To those 800 women, one to two controls were age-matched for a total of 1,129 controls. We used logistic regression models to estimate the relative risk (RR) of breast cancer associated with IGF levels.Findings: Among postmenopausal women, neither IGF-I, IGFBP-3, IGFBP-1, nor free IGF was associated with breast cancer risk [RRs, top versus bottom quintile: IGF-I, 1.0; 95% confidence interval (95% CI), 0.7-1.4; IGFBP-3, 0.8; 95% CI, 0.6-1.1; IGFBP-1, 0.9; 95% CI, 0.6-1.5; and free IGF, 1.0; 95% CI, 0.6-1.4]. Among premenopausal women, IGFBP-3, IGFBP-1, and free IGF similarly were not associated with breast cancer risk (RRs, top versus bottom quintile: IGFBP-3, 1.2; 95% CI, 0.8-2.3; IGFBP-1, 1.5; 95% CI, 0.8-3.0; and free IGF, 1.1; 95% CI, 0.7-2.1). Higher IGF-I plasma levels, however, were associated with a modestly elevated breast cancer risk (RR, 1.6; 95% CI, 1.0-2.6) among the premenopausal women, with a stronger association among premenopausal women ages < or =50 (RR, 2.5; 95% CI, 1.4-4.3); further adjustment for IGFBP-3 did not greatly change these estimates. INTERPRETATION: Circulating IGF-I levels seem to be modestly associated with breast cancer risk among premenopausal women, but not among postmenopausal women. IGFBP-3, IGFBP-1, and free IGF are not associated with breast cancer risk in either premenopausal or postmenopausal women in this cohort.     

Contraceptive methods and induced abortions and their association with the risk of colon cancer in Shanghai, China

267400 female textile workers in Shanghai, who were administered a questionnaire at enrollment into a randomised trial of breast self-examination between October 1989 and October 1991, were followed up until the middle of 2000. Based on the 655 women who developed colon cancer, rate ratios (RRs) were estimated and trends in risk assessed using Cox Proportional Hazards Models. Risk was increased in women who used oral contraceptives for over 3 years (RR=1.56, 95% Confidence Interval (CI) 1.01-2.40). A possible increase in risk was also observed in women who received progestational injections during pregnancy (RR=1.24, 95% CI 0.95-1.62), but not in relation to the use of injectable contraceptives. A possible reduction in risk was associated with tubal ligation (RR=0.86, 95% CI 0.71-1.03) and ever having had an induced abortion (RR=0.84, 95% CI 0.71-1.00). No trends in risk were observed in relation to the duration of hormonal contraceptive use or the number of induced abortions. Additional studies of the possible roles contraceptives may play in the aetiology of colon cancer in women at low risk of this disease are warranted.     

The association of soy food consumption with the risk of subtype of breast cancers defined by hormone receptor and HER2 status

Soy food intake has previously been associated with reduced breast cancer risk. Epidemiological evidence for subgroups of breast cancer, particularly by menopausal and hormone receptor status, is less consistent. To evaluate the role of hormone receptor and menopausal status on the association between soy food intake and breast cancer risk, we measured usual soy food intake in adolescence and adulthood via food frequency questionnaire in 70,578 Chinese women, aged 40–70 years, recruited to the Shanghai Women's Health Study (1996–2000). After a median follow‐up of 13.2 years (range: 0.01–15.0), 1,034 incident breast cancer cases were identified. Using Cox models, we found that adult soy intake was inversely associated with breast cancer risk [hazard ratio (HR) for fifth versus first quintile soy protein intake = 0.78; 95% confidence interval (CI):0.63–0.97]. The association was predominantly seen in premenopausal women (HR = 0.46; 95% CI:0.29‐0.74). Analyses further stratified by hormone receptor status showed that adult soy intake was associated with significantly decreased risk of estrogen receptor (ER)+/progesterone receptor (PR)+ breast cancer in postmenopausal women (HR = 0.72; 95% CI:0.53–0.96) and decreased risk of ER?/PR? breast cancer in premenopausal women (HR = 0.46; 95% CI:0.22–0.97). The soy association did not vary by human epidermal growth factor‐2 (HER2) status. Furthermore, we found that high soy intake during adulthood and adolescence was associated with reduced premenopausal breast cancer risk (HR = 0.53; 95% CI: 0.32–0.88; comparing third vs. first tertile) while high adulthood soy intake was associated with postmenopausal breast cancer only when adolescent intake was low (HR = 0.63; 95% CI: 0.43–0.91). Our study suggests that hormonal status, menopausal status and time window of exposure are important factors influencing the soy‐breast cancer association.