Modifiable risk factors for advanced vs. early breast cancer in the French E3N cohort

Advanced breast cancer (BC) is associated with heavier treatments and poorer prognosis than early BC. Despite mammographic screening, advanced BC incidence remains stable. Little is known about risk factors differentially associated with advanced BC. We analyzed factors predicting for postmenopausal advanced vs. early BC in the E3N cohort. E3N has been prospectively following 98,995 French women aged 50–65 years at baseline since 1990. Hazard ratios (HRs) and 95% confidence intervals (CIs) for advanced and early invasive BC were estimated with multivariate Cox competing risk hazard models. With a median follow-up of 15.7 years, 4,941 postmenopausal BC were diagnosed, including 1,878 (38%) advanced BC. Compared to early BC, advanced BC was differentially associated with excess weight (HR 1.39 [95% CI = 1.26–1.53] vs. 1.08 [95% CI = 1.00–1.17], p_homogeneity < 0.0001) and living in a rural area (HR 1.14 [95% CI = 1.00–1.31] vs. 0.93 [95% CI = 0.82–1.04], p_homogeneity 0.02). Excess weight was the only differential risk factor for advanced BC for hormone-dependent BC and for women compliant with screening recommendations. Previous mammography was associated with reduced advanced BC risk (HR 0.86 [95% CI = 0.73–1.00]) and increased early BC risk (HR 1.36 [95% CI = 1.18–1.56], p_homogeneity < 0.0001), but only for hormone-dependent BC. Excess weight appears to be mostly associated with advanced BC, especially hormone-dependent BC. These results add to the evidence for maintaining weight within the recommended limits.     

Selenium and the risk of postmenopausal breast cancer in the DOM cohort

Summary Selenium has been claimed to have chemo-preventive properties. However, data showing that in humans selenium levels are already decreased prior to diagnosis of breast cancer were not available. Such information is mandatory before oral selenium supplementation in the primary prevention of (breast) cancer in humans is acceptable. This question of a preventive-potential of selenium was evaluated in a case-control study nested in a cohort, because this design allows determination of the time-order of preceding selenium levels and subsequent cancer risk.The cohort consisted of 5577 women aged 55–70 years from the DOM project, a population based breast cancer screening program in the Netherlands. Instrumental Neutron Activation Analysis was used to measure the selenium content of toenail clippings. The 69 cases of breast cancer found during follow-up after screening represent recent tumours since all women had a negative screening mammogram 3–5 years previously.No decreased selenium levels, as measured in nail clippings from the big toes, could be detected in cases-to-be, either when compared to 4 age matched controls per case or when compared with a random control group drawn from the entire cohort. On the contrary, a tendency for slightly higher selenium levels among future cancer cases was observed.As to the sensitivity of detecting differences in selenium by nail clippings, lower selenium could be detected in nails of current smokers. The smoking-related decrease in nail selenium level was of the same order as the differences between breast cancer cases and controls, but was independent of the breast cancer risk.Results are similar to a comparable study on premenopausal breast cancer and argue against a preventive role for selenium on breast cancer risk.     

Cumulative number of menstrual cycles and breast cancer risk: results from the E3N cohort study of French women

Objective: To examine the relationship between breast cancer risk and the cumulative number of cycles before a first full-term pregnancy (FTP) and lifetime, taking age at menarche and at onset of regular cycling, periodicity and regularity of cycles, duration of periods of pregnancy, and lactation, oral contraceptive (OC) use, and age at menopause into account. Methods: The data were taken from the E3N prospective cohort study of women aged 40–65 years in 1990. A total of 1718 breast cancer cases were identified during the 579,525 person-years of follow-up. Results: There was a highly significant linear relationship between breast cancer risk and both the cumulative number of cycles before a first FTP (p for trend < 0.0001) and lifetime (p for trend < 0.001), with multivariate relative risk (RR) of a similar magnitude for both variables. Compared to women with a lifetime number of cycles 402 ( 30 years), the RR for those with a lifetime total of 403–441, 442–480, 481–520, and 521 cycles were 0.95 (0.75–1.21), 1.21 (0.97–1.52), 1.23 (0.96–1.58), and 1.60 (1.25–2.04), respectively. Results restricted to never OC users were similar. Conclusions: Further investigation is needed to clarify whether the underlying factor is repeated exposure to fluctuating hormones, the number of anovular/ovular cycles, or the relative importance of the follicular and luteal phases.     

Breast cancer risk factors and age at diagnosis: an Icelandic cohort study

An increasing number of studies indicates that the strength and even direction of association between breast cancer and established risk factors differ according to the woman's age when she develops the disease. This was studied in the setting of a population based cancer registry using a databank with information on age at menarche, parity, age at first birth, oral contraceptive (OC) use, lactation, height and weight. From a cohort of 80.219 women attending population-based cervical and breast cancer screening in Iceland, 1120 cases were identified, aged 26-90 years at diagnosis and 10,537 controls, individually matched to the cases on birth year and age when attending. Information given at last visit before diagnosis was used in the analysis, applying conditional logistic regression. Odds ratios and statistical strength of relationships varied according to age at diagnosis for age at first birth, number of births, duration of lactation, height and weight. The decreased risk associated with young age at first birth and increasing duration of breast feeding became less pronounced with advancing age at diagnosis. A reduced risk associated with an increasing number of births was not detected in women diagnosed under the age of 40. An increased risk associated with giving first birth after 30 years of age was mainly detected in women who had only given 1 birth and were diagnosed under the age of 40 (OR = 7.06 95% CI = 2.16-23.01). A positive association with height and especially with weight was confined to women diagnosed after the age of 55. The results confirm that age at diagnosis should be taken into account when studying the effects of breast cancer risk factors.     

The relation of breast size to breast cancer risk in postmenopausal women (United States)

Objective: Breast size has been hypothesized to predict a woman's risk of breast cancer although studies in the main have not supported an association. In a large, population-based case-control study we examined whether breast size might emerge as a significant risk factor among very lean women in whom breast size might be a truer reflection of the volume of gland mass at risk for malignant change.Methods: The data derive from a population-based case- control study of women aged 50 to 79 years conducted in several New England states and Wisconsin. Incident cases of invasive breast cancer (n=2015) were identified through state tumor registries and controls (n=2556) were selected at random within age strata from population lists. Telephone interviews were conducted to obtain information on known and suspected risk factors which included bra dimensions (cup and back size) prior to a first birth, or at the age of 20 for nulliparous women.Results: We observed a significant positive association for cup size which was limited to women who were the most lean as young adults based on chest circumference. Among those reporting a chest size under 34 inches multivariate-adjusted relative risks were 1.34 (95% CI: 1.04 to 1.74) for cup size B, and 1.76 (95% CI: 1.04 to 3.01) for cup size C and larger, compared to a cup size smaller than B, and the trend for increasing cup size was statistically significant (P=0.005). There was no relation with breast size among women reporting an average or larger back circumference (34 inches or larger).Conclusion: Breast size before a pregnancy is a positive predictor of postmenopausal breast cancer, but this association is limited to those who were especially lean as young women.     

Mediterranean diet adherence and risk of postmenopausal breast cancer: results of a cohort study and meta‐analysis

The Mediterranean Diet (MD) has been associated with reduced mortality and risk of cardiovascular diseases, but there is only limited evidence on cancer. We investigated the relationship between adherence to MD and risk of postmenopausal breast cancer (and estrogen/progesterone receptor subtypes, ER/PR). In the Netherlands Cohort Study, 62,573 women aged 55–69 years provided information on dietary and lifestyle habits in 1986. Follow‐up for cancer incidence until 2007 (20.3 years) consisted of record linkages with the Netherlands Cancer Registry and the Dutch Pathology Registry PALGA. Adherence to MD was estimated through the alternate Mediterranean Diet Score excluding alcohol. Multivariate case–cohort analyses were based on 2,321 incident breast cancer cases and 1,665 subcohort members with complete data on diet and potential confounders. We also conducted meta‐analyses of our results with those of other published cohort studies. We found a statistically significant inverse association between MD adherence and risk of ER negative (ER?) breast cancer, with a hazard ratio of 0.60 (95% Confidence Interval, 0.39–0.93) for high versus low MD adherence (p _trend = 0.032). MD adherence showed only nonsignificant weak inverse associations with ER positive (ER+) or total breast cancer risk. In meta‐analyses, summary HRs for high versus low MD adherence were 0.94 for total postmenopausal breast cancer, 0.98 for ER+, 0.73 for ER? and 0.77 for ER ? PR? breast cancer. Our findings support an inverse association between MD adherence and, particularly, receptor negative breast cancer. This may have important implications for prevention because of the poorer prognosis of these breast cancer subtypes.     

Relationship between estrogen receptors and risk factors of breast cancer in Japanese pre- and postmenopausal patients

Summary The relation between estrogen receptors (ER) in breast cancer and risk factors was studied in 456 Japanese patients. ER was shown to be positive in 55.3% (252/456) of patients. There was no difference in ER positivity between pre- and postmenopausal patients. In premenopausal patients, only the age at menarche and obesity showed some influence on the ER positivity of breast cancer. Among postmenopausal patients, on the contrary, ER(+) cancers were predominant in the patient groups that have been known to be higher in the risk of incidence of breast cancer. The factors included were the age at marriage, number of pregnancies, number of live children, and body weight. Of these, the body weight of patients was the strongest influence on the ER positivity in the postmenopausal patients. After excluding the effects of body weight, some of the reproductive factors such as number of pregnancies and number of live children were shown to be related to the ER status. These results may suggest the combination of lower incidence of breast cancer and lower percentage of ER(+) cancers in Japanese postmenopausal women as compared with the Western countries.     

Childhood and adult milk consumption and risk of premenopausal breast cancer in a cohort of 48,844 women - the Norwegian women and cancer study

The belief that life stress enhances breast cancer is common, but there are few prospective epidemiological studies on the relationship of life stress and breast cancer. We have investigated the association between stress of daily activities (SDA) and breast-cancer risk in a prospective cohort study of 10,519 Finnish women aged 18 years or more. SDA measures a subject's own appraisal of daily stress. It was assessed in 1975 and 1981 by a self-administered questionnaire, which also provided information on subject characteristics and other known breast-cancer risk factors. Follow-up data for breast cancer from 1976 to 1996 were attained through record linkage to the Finnish Cancer Registry. Study subjects were divided into 3 groups based on their SDA scores in 1975: no stress (23% of subjects), some stress (68%) and severe stress (9%). Hazard ratios (HRs) and respective 95% confidence intervals (CIs) for incidence of breast cancer by level of SDA were obtained from the Cox proportional hazards model. We identified 205 incident breast cancers in the cohort. Multivariable-adjusted HRs for breast-cancer risk were 1.00 (reference), 1.11 (95% CI 0.78-1.57) and 0.96 (95% CI 0.53-1.73) by increasing level of stress. Neither shifting of the SDA cut-off points nor restricting the analysis to women who reported the same level of SDA in 1975 and 1981 materially altered the results. We found no evidence of an association between self-perceived daily stress and breast-cancer risk.     

Reproductive risk factors in relation to molecular subtypes of breast cancer: Results from the nurses' health studies

Several intrinsic breast cancer subtypes, possibly representing unique etiologic processes, have been identified by gene expression profiles. Evidence suggests that associations with reproductive risk factors may vary by breast cancer subtype. In the Nurses' Health Studies, we prospectively examined associations of reproductive factors with breast cancer subtypes defined using immunohistochemical staining of tissue microarrays. Multivariate‐adjusted Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). Over follow‐up, we identified 2,063 luminal A, 1,008 luminal B, 209 HER2‐enriched, 378 basal‐like and 110 unclassified tumors. Many factors appeared associated with luminal A tumors, including ages at menarche (p_{heterogeneity} = 0.65) and menopause (p_{heterogeneity} = 0.05), and current HT use (p_{heterogeneity} = 0.33). Increasing parity was not associated with any subtype (p_{heterogeneity} = 0.76), though age at first birth was associated with luminal A tumors only (per 1‐year increase HR = 1.03 95%CI (1.02–1.05), p_{heterogeneity} = 0.04). Though heterogeneity was not observed, duration of lactation was inversely associated with risk of basal‐like tumors only (7+ months vs. never HR = 0.65 95%CI (0.49–0.87), p_trend = 0.02), p_{heterogeneity} = 0.27). Years between menarche and first birth was strongly positively associated with luminal A and non‐luminal subtypes (e.g. 22‐year interval vs. nulliparous HR = 1.80, 95%CI (1.08–3.00) for basal‐like tumors; p_{heterogeneity} = 0.003), and evidence of effect modification by breastfeeding was observed. In summary, many reproductive risk factors for breast cancer appeared most strongly associated with the luminal A subtype. Our results support previous reports that lactation is protective against basal‐like tumors, representing a potential modifiable risk factor for this aggressive subtype.     

Breast cancer risk factors and mammographic breast density in women over age 70

SummaryBackground Breast density is a strong risk factor for breast cancer, but little is known about factors associated with breast density in women over 70.Methods Percent breast density, sex hormone levels and breast cancer risk factor data were obtained on 239 women ages 70–92 recruited from 1986 to 1988 in the United States. Multivariable linear regression was used to develop a model to describe factors associated with percent density.Results Median (range) percent density among women was 23.7% (0–85%). Body mass index (β= −0.345, p<0.001 adjusted for age and parity) and parity (β= −0.277, p<0.001 adjusted for age and BMI) were significantly and inversely associated with percent breast density. After adjusting for parity and BMI, age was not associated with breast density (β=0.05, p=0.45). Parous women had lower percent density than nulliparous women (23.7 versus 34.7%, p=0.005). Women who had undergone surgical menopause had greater breast density than those who had had a natural menopause (33.4 versus 24.8%, p=0.048), as did women who were not current smokers (26.0 versus 17.3% for smokers, p=0.02). Breast density was not associated with age at menarche, age at menopause, age at first birth, breastfeeding, estrogen levels or androgen levels. In a multivariable model, 24% of the variance in percent breast density was explained by BMI (β= −0.35), parity (β=−0.29), surgical menopause (β=0.13) and current smoking (β= −0.12).Conclusion Factors associated with breast density in older, post-menopausal women differ from traditional breast cancer risk factors and from factors associated with breast density in pre-menopausal and younger post-menopausal women.     

Recreational physical activity and risk of postmenopausal breast cancer in a large cohort of US women

Due to its potential effects on ovarian hormone production, physical activity has been proposed as a modifiable risk factor for breast cancer. The authors analyzed data from the American Cancer Society Cancer Prevention Study II (CPS-II) Nutrition Cohort to examine the association between various measures of physical activity and postmenopausal breast cancer risk. Information on physical activity was obtained in 1992 via a self-administered questionnaire for 72,608 postmenopausal female participants who were cancer-free. During the five year prospective follow-up, 1520 incident breast cancer cases were identified among these women. Cox proportional hazards modeling was used to compute hazard rate ratios (RR) and to adjust for potential confounding factors including mammography. Women who were most physically active (>42.0 MET-h/week) at baseline had 29% lower incidence rates than active women with the least activity (>0–7.0 MET-h/week) (95% CI, 0.49–1.02). The difference in risk was largest for localized breast cancer, and for women who did not use hormone replacement therapy (HRT) at enrollment. Our findings are consistent with other studies that show lower risk of postmenopausal breast cancer associated with regular physical activity.     

Birth weight and risk of breast cancer in a cohort of 106,504 women

The possible association between prenatal factors and breast cancer has been discussed for more than a decade. Birth weight has been used commonly as a proxy measure for intrauterine growth. Whereas some previous studies have found support for an association between birth weight and breast cancer, others have been inconclusive or found no association. We investigated the relationship between birth weight and risk of female breast cancer in a cohort of 106,504 Danish women. Birth weights were obtained from school health records on girls born between 1930-1975. Information on breast cancer came from linking the cohort with the Danish Cancer Registry and the Danish Breast Cancer Cooperative Groups Registry. A total of 2,334 cases of primary breast cancer were diagnosed in the cohort during 3,255,549 person-years of follow-up among women with birth weight between 500-6,000 g. Of these, 922 (40%) were diagnosed with primary breast cancer at the age of 50 years or older. A significant association between birth weight and breast cancer was found equivalent to an increase in risk of 9% per 1,000 g increase in birth weight (95% CI 2-17). The increase was observed for all age groups, representing both pre- and post-menopausal women, and irrespective of tumor characteristics. Adjustment for age at first birth and parity did not influence the results. Birth weight is positively associated with risk of breast cancer, indicating that prenatal factors are important in the etiology of breast cancer.     

Analysis of menstrual, reproductive, and life-style factors for breast cancer risk in Turkish women

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.     

Hormonal and reproductive factors and risk of esophageal cancer in Chinese postmenopausal women: a case-control study

Aim: Since any relationship between hormonal and reproductive factors and risk of esophageal cancer is unclear, we investigated this question in Shandong province of China. Methods: A hospital-based 1:1 matched case-control study was conducted from January 2008 to November 2010, with face to face interviews conducted for 132 cases and 132 controls. All cases recruited in this study were confirmed by endoscopy and histological examination. Controls were first-visit outpatients who visited the same hosptial during the same period and were confirmed to have no malignancy. Conditional logistic regression analysis was employed to calculate risk of potential factors. Results: Esophageal cancer positive women had a higher prevalence of reflux, smoking status, lower BMI and less education than health controls(p<0.05).Women whose age of periods ended above 50 years and breastfed for more than 12 months had lower risk of esophageal cancer, with ORs (95% CI) of 0.42 (0.20-0.89) and 0.46 (0.21-0.98). Sensitivity analysis for the histological types of esophageal cancer showed no great difference between adenocarcinoma and squamous cell carcinoma. Conclusion: In summary, our findings suggest an inverse association between later age of menopause and duration of breastfeeding and risk of esophageal cancer. However, many reproductive and sex hormonal factors did not seem to be associated with esophageal cancer, supporting the need to further evaluate reproductive factors in prospective studies.     

Adiposity and breast cancer risk in postmenopausal women: Results from the UK Biobank prospective cohort

Body size is an important modifiable risk factor for postmenopausal breast cancer. However, it remains unclear whether direct measures of fat mass are better indicators of risk than anthropometric measures, or whether central adiposity may contribute to risk beyond overall adiposity. We analyzed data from 162,691 postmenopausal women in UK Biobank followed from 2006 to 2014. Body size was measured by trained technicians. Multivariable‐adjusted Cox regression was used to estimate relative risks. Analyses were stratified by age at recruitment, region and socioeconomic status, and adjusted for family history of breast cancer, age at menarche, age at first birth, parity, age at menopause, previous hormone replacement therapy use, smoking, alcohol intake, height, physical activity and ethnicity. We observed 2,913 incident invasive breast cancers during a mean 5.7 years of follow‐up. There was a continuous increase in risk of postmenopausal breast cancer with increasing adiposity, across all measures. The point estimate, comparing women in the top (median 37.6 kg) to bottom (median 17.6 kg) quartile of body fat mass was 1.70 (95% confidence interval 1.52–1.90). The magnitudes of the associations between per SD increase in BMI and body fat mass with breast cancer risk were similar, suggesting impedance measures of fat were not substantially better indicators of risk than anthropometric measures. After adjusting for body fat mass, the associations between anthropometric measures of central adiposity and breast cancer risk were attenuated. The magnitude of risk, across all measures of adiposity, was greater in women who had been postmenopausal for 12 or more years.     

Associations of reproductive time events and intervals with breast cancer risk: A report from the Shanghai Breast Cancer Study

While there is clear evidence for an association between later age at first live birth and increased breast cancer risk, associations with the timing of other reproductive events are less clear. As breast tissues undergo major structural and cellular changes during pregnancy, we examined associations between reproductive time events and intervals with breast cancer risk among parous women from the population‐based Shanghai Breast Cancer Study (SBCS). Unconditional logistic regression was used to evaluate associations with breast cancer risk for 3,269 cases and 3,341 controls. In addition to later age at first live birth, later ages at first pregnancy and last pregnancy were significantly associated with increased breast cancer risk (p‐trend = 0.002, 0.015, 0.008, respectively); longer intervals from menarche to first or last live birth were also associated with increased risk (p‐trend < 0.001, =0.018, respectively). Analyses stratified by menopausal status and estrogen receptor (ER)/progesterone receptor (PR) status revealed that associations for later age at first pregnancy or live birth and longer intervals from menarche to first or last live birth occurred among premenopausal women and ER+/PR+ breast cancers, whereas the association for later age at last pregnancy occurred among postmenopausal women and women with ER+/PR? or ER?/PR+ breast cancers. Because of the high correlation with other reproductive variables, models did not include adjustment for age at first live birth; when included, the significance of all associations was attenuated. These findings suggest that while reproductive time events and intervals play an important role in breast cancer etiology, contributions may differ by menopausal status and hormone receptor status of breast cancers.     

Body mass index,height, and postmenopausal breast cancer mortality in a prospective cohort of US women

Objective: Epidemiologic evidence suggests a positive association between body mass, adult height, and postmenopausal breast cancer. However, most studies have not been large enough to examine the association across a very wide range of body mass or height, and few studies have assessed the relationship between body mass or height and postmenopausal breast cancer mortality. Methods: The relation between body mass index (BMI) and height and postmenopausal breast cancer mortality was examined in the American Cancer Society's Cancer Prevention Study II (CPS-II), a large prospective mortality study of US adults enrolled in 1982. After 14 years of follow-up, 2852 breast cancer deaths were observed among 424,168 postmenopausal women who were cancer-free at interview. Cox proportional hazards modeling was used to estimate relative risks and to control for potential confounding. Results: Breast cancer mortality rates increased continually and substantially with increasing BMI (rate ratio (RR) = 3.08, 95% confidence interval (CI) = 2.09–4.51 for BMI 40.0 compared to BMI 18.5–20.49). If causal, the multivariate-adjusted RR estimates in this study correspond to approximately 30–50% of breast cancer deaths among postmenopausal women in the US population being attributable to overweight. Breast cancer mortality also increased with increasing height up to 66 inches with RR = 1.64, (95% CI = 1.23–2.18) in women 66 inches tall compared to those < 60 inches. Conclusions: Postmenopausal obesity is an important and potentially avoidable predictor of fatal breast cancer in this study. These results underscore the importance of maintaining moderate weight throughout adult life.     

Serum lipids and breast cancer risk: a cohort study of 5,207 Danish women

The association between serum lipids and breast cancer risk was investigated in a cohort of 5,207 Danish women, who participated in The Glostrup Population Studies between 1964 and 1986. During four to 26 years of follow-up, 51 incident cases of breast cancer were identified by linkage to the Danish Cancer Registry. At the time of lipid measurement, the women were between 30 and 80 years of age. An inverse association was found between serum high-density lipoprotein (HDL) cholesterol and risk of breast cancer, which was not changed by adjustment for potential confounders such as social class, age at menarche and menopause, number of full-term pregnancies, body mass index, or alcohol and coffee consumption. The relative risk was 0.3 (95 percent confidence interval = 0,1–0.8) for women in the highest quartile of serum HDL-cholesterol compared with women in the lowest quartile and the relation displayed a significant negative trend (P = 0.01). For serum triglycerides there was a suggestion of a positive association with breast cancer incidence, but the trend was not significant (P = 0.06). No relationship between total serum cholesterol or low-density lipoprotein cholesterol and risk of breast cancer was observed. Risk estimates for well known breast cancer risk factors such as social class, age at menopause, number of full-term pregnancies, and obesity were in the directions expected.Dr Høyer and Ms Engholm are with the Danish Cancer Registry, Copenhagen, Denmark; Dr Høyer is also with The Glostrup Population Studies, Glostrup, Denmark. Address correspondence to Dr Høyer at The Danish Cancer Registry, Institute of Cancer Epidemiology, Danish Cancer Society, Rosenvangets Hovedvej 35, DK-2100 Copenhagen Ø, Denmark. This study was funded by Sygekassernes Helsefond DK, Sundhedspuljen DK and the Danish Cancer Society.     

Case-control study of risk factors for breast cancer in Nigerian women

This study evaluated the potential risk factors for breast cancer in Nigerian women using a case-control design of 250 women with breast cancer and their age-matched female controls. Both cases and controls were recruited from 4 University Teaching Hospitals in Midwestern and Southeastern Nigeria. Data on the clinical and epidemiological characteristics were collected using interviewer-administered structured questionnaires. The mean age of the cases and controls were 46.1 and 47.1 years, respectively. Fifty-seven percent of the cases were premenopausal while 43% were postmenopausal. The association of risk factors with breast cancer was assessed using conditional logistic regression. Positive family history of breast cancer in first- and second-degree relatives (Odds ratio [OR] = 8.07, 95% confidence interval [CI], 1.003, 64.95, p = 0.04), education of high school level and above (OR = 1.35, 95% CI 1.04, 1.74, p = 0.0205), age at first fullterm pregnancy (FFTP) greater than 20 years (OR = 1.32 95% CI 1.01, 1.71, p = 0.0413) and waist/hip ratio (WHR) (OR = 1.98, 95% CI 1.27, 3.10, p = 0.0026) were associated with increased risk of breast cancer in the final multiple conditional logistic regression model. The findings from this study have shown that sociodemographic characteristics, reproductive variables and anthropometric measures are significant predictors of breast cancer risk in Nigerian women.     

Dietary polyunsaturated fatty acids and breast cancer risk in Chinese women: a prospective cohort study

Breast cancer is the most common cancer in women. Controversy exists regarding the role of dietary fat in breast cancer etiology. We investigated the association of dietary polyunsaturated fatty acids (PUFAs) and the ratio of n-6 PUFAs to marine-derived n-3 PUFAs with breast cancer risk in the Shanghai Women's Health Study, a prospective cohort study including 72,571 cancer-free participants at baseline. Dietary fatty acid intake was determined using food frequency questionnaires. We used Cox proportional hazards analysis to estimate the relative risks (RRs) and 95% confidence intervals (CIs) for the association of breast cancer risk with dietary fatty acids consumption. In 583,998 person-years of follow-up, we identified 712 breast cancer cases. We found no association of breast cancer risk to dietary intake of linoleic acid, arachidonic acid, α-linolenic acid or marine-derived n-3 PUFA. We found a statistically significant interaction between n-6 PUFA intake, marine-derived n-3 PUFA intake and breast cancer risk (p = 0.008). Women with lower intake (the lowest tertile) of marine-derived n-3 PUFA and higher intake (the highest tertile) of n-6 PUFA had an increase risk for breast cancer (RR = 2.06; 95% CI = 1.27-3.34) compared to women with higher intake (the highest tertile) of marine-derived n-3 PUFAs and lower intake (the lowest tertile) of n-6 PUFAs after adjusting for potential confounders. The relative amounts of n-6 PUFA to marine-derived n-3 PUFAs may be more important for breast cancer risk than individual dietary amounts of these fatty acids.