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.     

The association between stressful life events and breast cancer risk: a meta-analysis

Breast cancer is the most prevalent cancer in women in Western societies. Studies examining the relationship between stressful life events and breast cancer risk have produced conflicting results. The purpose of this meta-analysis was to identify studies on this relationship, between 1966 and December 2002, to summarize and quantify the association and to explain the inconsistency in previous results. Summary odds ratios and standard errors were calculated, using random effect meta-regression analyses, for the following categories: stressful life events, death of spouse, death of relative or friend, personal health difficulties, nonpersonal health difficulties, change in marital status, change in financial status and change in environmental status. The presence of publication bias has been explored, and sensitivity analyses were performed to identify heterogeneity, using calculation of the percentage of variability due to heterogeneity, meta-regression analyses and stratification. Only the categories stressful life events (OR = 1.77, 95% CI 1.31-2.40), death of spouse (OR = 1.37, 95% CI 1.10-1.71) and death of relative or friend (OR = 1.35, 95% CI 1.09-1.68) showed a statistically significant effect. Publication bias was identified in both stressful life events (p = 0.00) and death of relative or friend (p = 0.02). Sensitivity analyses resulted in the identification of heterogeneity in all categories, except death of spouse. The results of this meta-analysis do not support an overall association between stressful life events and breast cancer risk. Only a modest association could be identified between death of spouse and breast cancer risk.     

The impact of reproductive factors on breast cancer risk - The feasibility of using Swedish population-based registers to account for the effect of confounding in cohort studies

Objective The aim of this study was to analyze the impact of reproductive factors on breast cancer risk among Swedish women by using nationwide population registers.Methods A cohort including all Swedish women born between 1920 and 1959 was followed up to 1997 by record linkage to different population-based registers. More than 4 million children were linked to the women in the cohort and 60,328 women were diagnosed with breast cancer. Poisson regression was used to model the breast cancer incidence by risk groups. In a sub-cohort of 18,164 women irradiated for skin hemangioma in infancy, the breast cancer risk was analyzed in relation to radiation dose and accounting for reproductive factors.Results The relative breast cancer risk (RR) for the reproductive factors was 0.35 [ 95% confidence interval (CI) 0.30-0.42] for women with 6 or more children and the first child before the age of 20 years, and RR was 1.11 (95% CI 1.06-1.18) for uniparous women with the first child at age 35 years or older, compared to nulliparous women. The discrepancies of reproductive factors in the hemangioma cohort compared to Swedish women had a minor effect on RR, with a reduction from 1.13 (95%CI 1.00-1.26) to 1.11 (95% CI 0.99-1.25).Conclusions This study shows the feasibility of using population-based registers to retrieve reliable information on reproductive factors to eliminate its confounding effect when analyzing other risk factors.     

Family history of cancer and risk of ovarian cancer

The aim of this study was to examine the relationship between history of cancer in first-degree relatives and ovarian cancer risk. Between 1992 and 1999, we conducted a case-control study in Italy on 1031 women with epithelial ovarian cancer and 2411 women admitted to hospital for acute non-neoplastic conditions. Odds ratios (OR) were estimated using unconditional logistic regression, adjusted for age and several potential confounders. Overall, 27 cases and nine controls reported a family history of ovarian cancer (OR = 7.0; 95% confidence interval (CI) 3.1-16). The OR was 23 (95% CI 2.6-212) below age 50 years, based on 10 cases and one control only. The risk of ovarian cancer was also increased in women with a family history of cancer of the stomach (OR = 1.5; 95% CI 1.0-2.1), intestine (OR = 1.7; 95% CI 1.2-2.4), lung (OR = 1.3; 95% CI 1.0-1.8), breast (OR = 2.3; 95% CI 1.7-3.1), lymphomas (OR = 2.3; 95% CI 1.0-5.1) and all sites (OR = 1.6; 95% CI 1.4-1.9). Our results confirm the higher ovarian cancer risk in women with a family history of ovarian and breast cancer, and suggest a few associations with other sites.     

克拉玛依市区女性乳腺癌危险因素的病例对照研究

 目的　探讨克拉玛依市区女性乳腺癌的危险因素。方法　用病例对照研究方法调查129例女性乳腺癌和对应的129名对照者,用Logistic回归模型进行乳腺癌危险因素分析。结果　乳腺癌的危险因素有乳腺癌家族史（OR＝2.744,95 % CI＝1.884～4.674）、乳腺增生症（OR＝1.423,95 % CI＝1.160～1.810）、 乳腺炎（OR＝2.363,95 % CI＝2.039～3.934）、子宫肌瘤（OR＝1.623,95 % CI＝1.263～2.024）、 流产（OR＝1.723,95 % CI＝1.143～2.600）、 饮酒（OR＝1.243,95 % CI＝1.040～1.483）、精神创伤（OR＝2.184,95 % CI＝1.753～3.025）、长期接触电离辐射（OR＝1.374,95 % CI＝1.152～1.699）; 保护因素有初潮年龄增大（OR＝0.773,95 % CI＝0.674～0.956）、累计哺乳时间（OR＝0.672,95 % CI＝0.480～0.941）、坚持运动（OR＝0.572,95 % CI＝0.391～0.837）。结论　以上11个因素为克拉玛依市区女性乳腺癌重要的危险因素和保护因素。     

Risk Factors for breast cancer among japanese women: A case-control study in Ibaraki, Japan

BACKGROUND: The number of epidemiologic studies on breast cancer risk factorsin Japanese women is still quite limited. Our objective was to clarify the relationship between lifestyle, body size and breast cancer risk. METHODS: A matched case-control study was conducted in Ibaraki, Japan. The participants were 148 women aged 26-69 diagnosed with breast cancer at Tsukuba University Hospital or Tsukuba Medical Center Hospital between January, 1990 and March, 1997. Two controls were individually matched to the cases by age and residence. A self-administered questionnaire was used to obtain information on the family history of breast cancer, reproductive history, education, body size and lifestyle factors. Conditional logistic regression analysis was used to estimate oddsratios (ORs)and 95% confidence intervals (95% CI). RESULTS: After adjustment for potential confounders, heavy weight and higher body mass index were associated with an increased risk of breast cancer among postmenopausal women (OR = 1.76, 95% CI = 0.69, 4.48; OR = 1.57, 95% CI=0.61, 3.99, respectively). Current or ex-smokers were found to be at an increased risk for breast cancer (OR = 3.33; 95% CI = 1.63, 6.80). Women who take hot baths had a decreased risk for breast cancer (OR = 0.67; 95% CI = 0.43, 1.06). Recreational physical activity was associated with a reduced risk of breast cancer (PTrend = 0.005).OR for breast cancer among physically active women was 0.36 (95% CI = 0.19, 0.70), as compared with inactive women. Taller women had an increased risk of breast cancer relative to shorter women (OR = 1.49; 95% CI = 0.83, 2.70). No significant association between alcohol consumption and breast cancer risk was detected. CONCLUSION: Our results suggest that several potentially modifiable lifestyle factors may be useful for the prevention of breast cancer.     

Analysis of menstrual, reproductive, and life-style factors for breast cancer risk in Turkish women: a case-control study

The aim of this study was to investigate the association between menstrual, reproductive, and life-style factors and breast cancer in Turkish women. In a hospital-based case-control study in Ankara, 622 patients with histologically confirmed breast cancer were compared with 622 age-matched controls, admitted to the same hospital for acute and non-neoplastic diseases. Unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CI) related to risk factors. Overall, menopausal status and age at menopause were found to be significantly associated with breast cancer. Having a full-term pregnancy and early age at first birth were associated with decreased breast cancer risk (OR = 0.45, 95% CI = 0.30-0.66; OR = 0.34, 95% CI = 0.22-0.53, respectively). Postmenopausal women with lactation longer than 48 mo had reduced risk of breast cancer (OR = 0.36, 95% CI = 0.14-0.93). In conclusion, decreased parity, late age at first birth, early menopause, and shorter duration of lactation were the most important determinants of breast cancer risk in Turkish women.     

Breast cancer risk in symptomatic women spontaneously undergoing clinical breast examination

Breast cancer (BC) is the most common cancer among women. However, few studies consider the possible relationship between the main breast complaints referred to by non-screened patients and cancer onset. The objective of this study was to evaluate the relationship between the principal breast complaints (breast pain, breast lump and nipple discharge) and the risk of BC. A group of 347 symptomatic women (median age 59 years, range 35-83) with confirmed BC (cases) was age-matched with a population-based group of 351 symptomatic women (controls) who were followed-up for at least three years (median 78 months, range 36-146) to exclude the presence of a missed BC. Breast pain was the most common (p < 0.05) complaint in younger patients (50 years or less = 39.0%, 51-60 years = 51.2%), while breast lump was most common in patients aged > 60 years (65.4%). Since the odds ratio (OR) ranged from 0.80 to 1.20 at a 95% confidence interval (CI) of 0.54-1.80, there was no overall significant association between breast complaints and risk of BC. There was some evidence of increased risk among patients with breast lump (OR = 1.20, 95% CI 0.80-1.80), and no risk in those with breast pain (OR = 0.86, 95% CI 0.54-1.36) and nipple discharge (OR = 0.8, 95% CI 0.37-1.74). In conclusion, a relationship between breast complaints and the onset of BC does not seem to exist.     

Effect of pregnancy as a risk factor for breast cancer in BRCA1/BRCA2 mutation carriers

Early age at first birth and multiparity have been associated with a decrease in the risk of breast cancer in women in the general population. We examined whether this relationship is also present in women at high risk of breast cancer due to the presence of a mutation in either of the 2 breast cancer susceptibility genes, BRCA1 or BRCA2. We performed a matched case-control study of 1,260 pairs of women with known BRCA1 or BRCA2 mutations, recruited from North America, Europe and Israel. Women who had been diagnosed with breast cancer were matched with unaffected control subjects for year of birth, country of residence, and mutation (BRCA1 or BRCA2). Study subjects completed a questionnaire detailing their reproductive histories. Odds ratios (ORs) and 95% confidence intervals (CIs) were derived by conditional logistic regression. Among BRCA1 carriers, parity per se was not associated with the risk of breast cancer (OR for parous vs. nulliparous = 0.94; 95% CI = 0.75-1.19; p = 0.62). However, women with a BRCA1 mutation and 4 or more children had a 38% decrease in breast cancer risk compared to nulliparous women (OR = 0.62; 95% CI = 0.41-0.94). In contrast, among BRCA2 carriers, increasing parity was associated with an increased risk of breast cancer; women with 2 or more children were at approximately 1.5 times the risk of breast cancer as nulliparous women (OR = 1.53; 95% CI = 1.01-2.32; p = 0.05). Among women with BRCA2 mutations and who were younger than age 50, the (adjusted) risk of breast cancer increased by 17% with each additional birth (OR = 1.17; 95% CI = 1.01-1.36; p = 0.03). There was no significant increase in the risk of breast cancer among BRCA2 carriers older than 50 (OR for each additional birth = 0.97; 95% CI = 0.58-1.53; p = 0.92). In the 2-year period following a birth, the risk of breast cancer in a BRCA2 carrier was increased by 70% compared to nulliparous controls (OR = 1.70; 95% CI = 0.97-3.0). There was a much smaller increase in breast cancer risk among BRCA2 carriers whose last birth was 5 or more years in the past (OR = 1.24; 95% CI = 0.79-1.95). A modest reduction in risk of breast cancer was observed among BRCA1 carriers with 4 or more births. Among BRCA2 carriers, increasing parity was associated with a significant increase in the risk of breast cancer before age 50 and this increase was greatest in the 2-year period following a pregnancy.     

Clinical Risk Factor Analysis for Breast Cancer: 568,000 Subjects Undergoing Breast Cancer Screening in Beijing, 2009

Objectives: Although there are many reports about the risk of breast cancer, few have reported clinicalfactors including history of breast-related or other diseases that affect the prevalence of breast cancer. This studyexplores these risk factors for breast cancer cases reported in Beijing in 2009. Materials and Methods: Datawere derived from a Beijing breast cancer screening performed in 2009, of 568,000 women, from 16 districts ofBeijing, all aged between 40 and 60 years. In this study, multilevel statistical modeling was used to identify clinicalfactors that affect the prevalence of breast cancer and to provide more reliable evidence for clinical diagnosticsby using screening data. Results and Conclusion: Those women who had organ transplants, compared withthose with none, were associated with breast cancer with an odds ratio (OR) = 65.352 [95% confidence interval(CI): 8.488-503.165] and those with solid breast mass compared with none had OR = 1.384 (95% CI: 1.022-1.873). Malignant tendency was strongly associated with increased risk of breast cancer, OR = 207.999(95%CI: 151.950-284.721). The risk of breast cancer increased with age, OR1 = 2.759 (95% CI: 1.837-4.144, 56-60 vs.40-45), OR2 = 2.047 (95% CI: 1.394-3.077, 51-55 vs. 40-45), OR3 = 1.668 (95% CI: 1.145-2.431). Normal resultsof B ultrasonic examination show a lower risk among participants, OR= 0.136 (95% CI: 0.085-0.218). Thosewomen with ductal papilloma compared with none were associated with breast cancer, OR=6.524 (95% CI:1.871-22.746). Therefore, this study suggests that clinical doctors should pay attention to these high-risk factors.     

Physical activity and breast cancer risk in women aged 20-54 years

BACKGROUND/METHODS: Although several studies have suggested that physical activity is associated with a decreased risk of breast cancer, such a decrease has not been found consistently, perhaps because physical activity was assessed in different ways and for restricted periods. Few studies have assessed the risk of breast cancer in relation to lifetime physical activity. We used data from a population-based, case-control study, including 918 case subjects (aged 20-54 years) and 918 age-matched population control subjects, to examine associations between breast cancer risk and physical activity at ages 10-12 years and 13-15 years, lifetime recreational activity, and title of longest held job. RESULTS: Women who were more active than their peers at ages 10-12 years had a lower risk of breast cancer (odds ratio [OR] = 0.68; 95% confidence interval [CI] = 0.49-0.94). Women who had ever engaged in recreational physical activity had a reduced risk of breast cancer compared with inactive women (OR = 0.70; 95% CI = 0.56-0.88). Neither very early recreational activity (before age 20 years) nor recent activity (last 5 years) was associated with a greater reduction in risk than recreational activity in the intermediate period. Furthermore, women who started recreational activities after age 20 years and women who started earlier and continued their activities throughout adult life experienced a similar reduction in risk. Lean women, i.e., women with a body mass index (weight in kg/[height in m](2)) less than 21. 8 kg/m(2), appeared to have a lower risk associated with recreational physical activity than women with a body mass index greater than 24.5 kg/m(2) (OR = 0.57 [95% CI = 0.40-0.82] and OR = 0. 92 [95% CI = 0.65-1.29], respectively). CONCLUSIONS: Our findings support the hypothesis that recreational physical activity is associated with a decreased risk of breast cancer. Physical activity in early or recent life does not appear to be associated with additional beneficial effects.     

Radiation dose,chemotherapy and risk of lung cancer after breast cancer treatment

It is of particular concern to evaluate the risk of lung cancer occurrence after breast cancer treatment as women with breast cancer quite often undergo radiation therapy as part of their initial treatment and their life expectancy remains long. From a roster of 7711 women initially treated for breast cancer between 1954 and 1984, a cohort-study was performed among 4171 1-year survivors followed during the period 1975-1995. The relationship between the radiation dose received by the lung and the risk of lung cancer was then evaluated in a nested case-control study of 11 breast-cancer patients who developed lung cancer and 22 controls matched for age at diagnosis of breast cancer, period of initial treatment and length of follow-up. Among the 4171 women, six developed lung cancer during the entire follow-up as compared to 5.4 cases expected (SIR = 1.1, 95% CI: 0.4-2.3). When considering only the women initially treated by radiotherapy with or without adjunction of chemotherapy and excluding the 10 first years of follow-up, the SIR was significantly increased (SIR = 3.2, 95%CI: 1.0-7.4). In the case-control study, nine of the 11 lung cancers occurred in the ipsilateral lung and two in the trachea. The overall odds ratio (OR) of lung cancer associated with initial radiotherapy was 1.4 (95% CI: 0.2-11.1) and an excess in the OR of 7% (90% CI: ? to 41%, p = 0.10) per gray delivered to the site of lung cancer was evidenced. Our results agree with previous studies in favor of an increased risk of lung cancer after radiation therapy for breast cancer.     

Risk factors by molecular subtypes of breast cancer across a population-based study of women 56 years or younger

Differences in incidence, prognosis, and treatment response suggest gene expression patterns may discern breast cancer subtypes with unique risk factor profiles; however, previous results were based predominantly on older women. In this study, we examined similar relationships in women ≤ 56 years, classified by immunohistochemical staining for estrogen receptor, progesterone receptor, and human epidermal growth factor receptor-2 for 890 breast cancer cases and 3,432 frequency-matched population-based controls. Odds ratios (OR) and 95% confidence intervals (CI) for tumor subtypes were calculated using multivariate polytomous regression models. A total of 455 (51.1%) tumors were considered luminal A, 72 (8.1%) luminal B, 117 (13.1%) non-luminal HER-2/neu+, and 246 (27.6%) triple negative. Triple negative tumors were associated with breast feeding duration (per 6 months: OR = 0.76, 95% CI 0.64-0.90). Among premenopausal women, increasing body size was more strongly associated with luminal B (OR = 1.73, 95% CI 1.07-2.77) and triple negative tumors (OR = 1.67, 95% CI 1.22-2.28). A history of benign breast disease was associated only with increased risk of luminal A tumors (OR = 1.89, 95% CI 1.43-2.50). A family history of breast cancer was a risk factor for luminal A tumors (OR = 1.93, 95% CI 1.38-2.70) regardless of age, and triple negative tumors with higher risks for women <45 (OR = 5.02, 95% CI 2.82-8.92; P for age interaction = 0.005). We found that little-to-no breastfeeding and high BMI were associated with increased risk of triple negative breast cancer. That some risk factors differ by molecular subtypes suggests etiologic heterogeneity in breast carcinogenesis among young women.     

Lactation and breast cancer risk: a case-control study in Connecticut

In this report, we examined the relationship between lactation and breast cancer risk, in a case-control study of breast cancer, conducted in Connecticut between 1994 and 1998. Included were 608 incident breast cancer cases and 609 age frequency matched controls, aged 30-80 years old. Cases and controls were interviewed by trained study interviewers, using a standardized, structured questionnaire, to obtain information on lactation and other major risk factors. Parous women who reported ever lactation had a borderline significantly reduced risk of breast cancer (OR = 0.83, 95% CI, 0.63-1.09). An OR of 0.53 (95% CI, 0.27-1.04) was observed in those having breastfed more than 3 children compared to those who never lactated. Women having breastfed their first child for more than 13 months had an OR of 0.47 (95% CI, 0.23-0.94) compared to those who never breastfed. Lifetime duration of lactation also showed a risk reduction while none of the ORs were statistically significant. Further stratification by menopausal status showed a risk reduction related to lactation for both pre- and postmenopausal women, while the relationship is less consistent for the latter. These results support an inverse association between breastfeeding and breast cancer risk.     

Polymorphic catechol-O-methyltransferase gene and breast cancer risk.

We examined 483 Finnish breast cancer cases and 482 population controls to determine the potential effect of catechol-O-methyltransferase (COMT) genotype in individual susceptibility to breast cancer. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by unconditional logistic regression after adjustment for known or suspected risk factors for breast cancer. When studied separately by menopausal status, the COMT-L allele-containing genotypes were inversely associated with premenopausal breast cancer, especially with advanced stage of the disease (OR, 0.44; 95% CI, 0.22-0.87). Among postmenopausal women a similar decreased risk was seen for local carcinoma associated with the COMT-LL genotype (OR, 0.55; 95% CI, 0.31-0.98). The lowest breast cancer risk was seen in the postmenopausal women with the COMT-LL genotype and low body-mass index (30 months) use of estrogen (OR, 4.02; 95% CI, 1.13-14.3), or with the COMT-L allele-containing genotypes and early age (相似文献   

Risk factors for breast cancer at young ages in twins: an international population-based study

BACKGROUND: Breast cancer etiology in women may relate to exposures early in life as well as in adulthood, but it has been difficult to gain information on childhood variables, and evidence on their effects is very limited. Comparison of risk factor levels between affected probands and unaffected twins in twin pairs can provide a unique method to investigate risk factors that act in early life. METHODS: We conducted four population-based case-control studies of breast cancer risk in twins in Denmark, England and Wales, Finland, and Sweden and pooled the data from these studies. The case patients were 400 women with incident breast cancer before the age of 50 years, and the control subjects were their twin sisters who had not had breast cancer by that time. Data on risk factors (e.g., demographic and anthropomorphic variables, reproductive history, and family history) were collected by interview and by a mailed questionnaire and were analyzed by calculating matched odds ratios [ORs]. All statistical tests were two-sided. RESULTS: The risk of breast cancer was increased for women who were less obese (OR = 1.44, 95% confidence interval [CI] = 1.08 to 1.91) or taller (OR = 1.27, 95% CI = 0.95 to 1.70) than their co-twin at age 10 years, for women who developed breasts earlier than their co-twin (OR = 1.53, 95% CI = 1.14 to 2.06), and for women who had a smaller waist-to-hip ratio at age 20 years than their co-twin (OR = 1.79, 95% CI = 1.00 to 3.21). Analysis according to family history of breast cancer showed that the associations of childhood height and weight with risk of breast cancer were only apparent in women without a family history of breast cancer. CONCLUSIONS: Childhood growth before puberty may affect the risk of premenopausal breast cancer, at least in women without a family history of breast cancer. The distribution of body fat in young adulthood may also be related to breast cancer risk.     

The Investigation of Risk Factors Impacting Breast Cancer in Guilan Province

Introduction: Breast cancer is multifactorial therefore more recognition of risk factors is important in its prevention. Objective: This study was conducted in order to determine the factors influencing breast cancer in women referred to health centers in Guilan province in 2015-2016. Method: In a case- control study, 225 women with breast cancer were investigated. The control group consisted of 225 healthy women of the relatives (third-rank) whose phone numbers were obtained from the patients. Data were collected through telephone interviews. Results: The risk of breast cancer raised in women who have a family history of other cancers (OR= 3.5; 95% CI= 1.96-6.6) ,exposure to X-Ray (OR= 2.5; 95% CI=1.1-5.5), having more than 4 children (OR= 2.695% CI=1.2-4.8), age more than 36 years at first pregnancy(OR=2.3; 95% CI=0.7-5.1),primary levelof education (OR= 5.4;95% CI=2.8-11.2) and inadequate intake of fruit (OR=1.5; 95% CI=1-2.2). Also, presence of the following factors reduced breast cancer risk: regular menstruation (OR= 0.66; CI=0.4- 0.9), duration of breastfeeding more than 12 months, less than 6 months and 7-12 months (OR=0.23; 95% CI=0.09-0.59 , OR=0.29; 95% CI=0.17-0.49 and OR=0.03; 95% CI=0.01-0.08) and parity (OR=0.4; 95% CI=0.27-0.83) In multiple linear regression analysis of higher education (OR=0.16; 95% CI=0.03-0.77), using contraceptives for more than 16 years (OR=2.3; 95% CI=1.4-3.9), family history of other cancers (OR=6.1; 95% CI=1.9-19.3) and a history of X-Ray exposure (OR=4.4; 95% CI=1.07-18.1) were considered as predictive factors. Conclusion: The results of this study emphasize the importance of informing women about breast cancer risk factors. So, identification of these risk factors is required as important means of prevention and treatment of breast cancer.     

Risk factors for breast cancer in nulliparous women

The relation between hormonal and lifestyle factors and breast cancer risk in nulliparae was investigated using data from two case-control studies conducted in Italy between 1983 and 1994. The study included 1041 nulliparae with histologically confirmed incident breast cancer and 1002 nulliparous controls admitted to hospital for a wide range of acute, non-neoplastic, nonhormone-related diseases. In premenopausal nulliparae, there was an inverse relation with age at menarche [odds ratios (OR) 0.45; 95% confidence intervals (CI) 0.24-0.86 for > or = 15 years vs < 12], while no association emerged in postmenopausal. Breast cancer risk increased with age at menopause, the OR being 1.91 (95% CI 1.26-2.90) for nulliparae reporting age at menopause > or = 53 years compared with < 45. Abortion was not related to breast cancer risk, the OR being 0.92 for any spontaneous, 0.97 for any induced and 0.77 for > or = 2 total abortions compared to none. The OR was 1.75 (95% CI 1.03-2.97) for women reporting their first abortion at age > or = 30 years compared with < 30. Oral contraceptives and hormone replacement therapy in menopause were moderately related to risk. The OR was 2.71 (95% CI 1.85-3.95) in nulliparae with a family history of breast cancer and 1.60 (95% CI 1.20-2.14) in those with a history of benign breast disease. Compared with nulliparae reporting a low physical activity, the OR was 0.79 (95% CI 0.54-1.16) for those reporting intermediate/high activity. Breast cancer risk increased with total energy intake, the OR being 1.65 (95% CI 0.99-2.75) in the highest tertile; beta-carotene was inversely related to risk (OR 0.60, 95% CI 0.38-0.95) for the highest tertile. Thus, most risk factors for breast cancer in nulliparae were similar to those in women generally.     

Risk factors for subsequent invasive breast cancer and breast cancer death after ductal carcinoma in situ: a population-based case-control study in Sweden.

In a case-control study derived from a cohort of 4661 women with a primary carcinoma in situ of the breast, we investigated age at diagnosis, mode of detection, tumor characteristics, and primary therapy, as prognostic factors for developing invasive breast cancer or dying from breast cancer. From all of the women with a primary carcinoma in situ reported to the Swedish Cancer Registry from 1960 through 1992, we selected as cases all of the women with a ductal carcinoma in situ who later died of breast cancer (n = 39) or who developed a subsequent invasive cancer in either breast (n = 118). From this cohort, we also selected controls matched to the cases by year of diagnosis and health care region. We conducted univariate and multivariate analyses to study the association between risk of invasive cancer or death and the different risk factors. Large size, diameter > or = 25 mm [odds ratio (OR), 3.5; 95% confidence interval (CI), 1.1-11.4] and multifocality (OR, 3.9; 95% CI, 1.2-12.7) increased the risk of breast cancer death in univariate analysis. Postoperative radiotherapy (OR, 0.1; 95% CI, 0.0-1.0) and mastectomy (OR, 0.1-95% CI, 0.0-0.5) lowered the risk of an ipsilateral invasive cancer in multivariate analysis. The risk pattern by treatment category differed between those who had an ipsilateral invasive cancer and those who either had a contralateral cancer or died from breast cancer. The driving forces behind local and generalized disease may differ. Because confounding by indication may influence the effects of different treatments, the results should be interpreted with caution.     

Obstetric history and mammographic density: a population-based cross-sectional study in Spain (DDM-Spain)

High mammographic density (MD) is used as a phenotype risk marker for developing breast cancer. During pregnancy and lactation the breast attains full development, with a cellular-proliferation followed by a lobular-differentiation stage. This study investigates the influence of obstetric factors on MD among pre- and post-menopausal women. We enrolled 3,574 women aged 45-68 years who were participating in breast cancer screening programmes in seven screening centers. To measure MD, blind anonymous readings were taken by an experienced radiologist, using craniocaudal mammography and Boyd's semiquantitative scale. Demographic and reproductive data were directly surveyed by purpose-trained staff at the date of screening. The association between MD and obstetric variables was quantified by ordinal logistic regression, with screening centre introduced as a random effect term. We adjusted for age, number of children and body mass index, and stratified by menopausal status. Parity was inversely associated with density, the probability of having high MD decreased by 16% for each new birth (P value < 0.001). Among parous women, a positive association was detected with duration of lactation [>9 months: odds ratio (OR) = 1.33; 95% confidence interval (CI) = 1.02-1.72] and weight of first child (>3,500 g: OR = 1.32; 95% CI = 1.12-1.54). Age at first birth showed a different effect in pre- and post-menopausal women (P value for interaction = 0.030). No association was found among pre-menopausal women. However, in post-menopausal women the probability of having high MD increased in women who had their first child after the age of 30 (OR = 1.53; 95% CI = 1.17-2.00). A higher risk associated with birth of twins was also mainly observed in post-menopausal women (OR = 2.02; 95% CI = 1.18-3.46). Our study shows a greater prevalence of high MD in mothers of advanced age at first birth, those who had twins, those who have breastfed for longer periods, and mothers whose first child had an elevated birth weight. These results suggest the influence of hormones and growth factors over the proliferative activity of the mammary gland.