A prospective study of adiposity and postmenopausal breast cancer risk: the Malmö Diet and Cancer Study

Mitochondrial Ca2+ signaling is a hallmark of specific adipose tissue-cancer crosstalk

Obesity is associated with increased risk and worse prognosis of many tumours including those of the breast and of the esophagus. Adipokines released from the peritumoural adipose tissue promote the metastatic potential of cancer cells, suggesting the existence of a crosstalk between the adipose tissue and the surrounding tumour. Mitochondrial Ca2+ signaling contributes to the progression of carcinoma of different origins. However, whether adipocyte-derived factors modulate mitochondrial Ca2+ signaling in tumours is unknown. Here, we show that conditioned media derived from adipose tissue cultures (ADCM) enriched in precursor cells impinge on mitochondrial Ca2+ homeostasis of target cells. Moreover, in modulating mitochondrial Ca2+ responses, a univocal crosstalk exists between visceral adipose tissue-derived preadipocytes and esophageal cancer cells, and between subcutaneous adipose tissue-derived preadipocytes and triple-negative breast cancer cells. An unbiased metabolomic analysis of ADCM identified creatine and creatinine for their ability to modulate mitochondrial Ca2+ uptake, migration and proliferation of esophageal and breast tumour cells, respectively.

New role of fat-free mass in cancer risk linked with genetic predisposition

Cancer risk is associated with the widely debated measure body mass index (BMI). Fat mass and fat-free mass measurements from bioelectrical impedance may further clarify this association. The UK Biobank is a rare resource in which bioelectrical impedance and BMI data was collected on ~ 500,000 individuals. Using this dataset, a comprehensive analysis using regression, principal component and genome-wide genetic association, provided multiple levels of evidence that increasing whole body fat (WBFM) and fat-free mass (WBFFM) are both associated with increased post-menopausal breast cancer risk, and colorectal cancer risk in men. WBFM was inversely associated with prostate cancer. We also identified rs615029[T] and rs1485995[G] as associated in independent analyses with both PMBC (p = 1.56E-17 and 1.78E-11) and WBFFM (p = 2.88E-08 and 8.24E-12), highlighting splice variants of the intriguing long non-coding RNA CUPID1 (LINC01488) as a potential link between PMBC risk and fat-free mass.

Comprehensive evaluation of body composition in a wide age range of Iranian adults using bioelectrical impedance analysis: Tehran Lipid and Glucose Study

OBJECTIVE

To evaluate sex- and age-stratified body composition (BC) parameters in subjects with wide age range of 20-79 years.

DESIGN

Cross-sectional.

SETTING

Participants of Tehran Lipid and Glucose Study (TLGS).

PARTICIPANTS

Two thousand nine hundred seventy participants met our inclusion criteria. They were divided into five age groups, and BC parameters were analysed based on sex and age using a bioelectrical impedance analyser (BIA).

RESULT

The mean age of the participants was 42·1 ± 12·5 years, and 54 % of them were males. The mean BMI was 26·7 ± 3·7 kg/m2. Obesity indices were significantly higher in females (P < 0·001); however, skeletal muscle mass (SMM) and fat-free mass (FFM) were significantly higher in males (P < 0·001). Both SMM and FFM decreased significantly after the age of 50 years. Obesity indices significantly increased from the age group of 20-29 to 30-39 years in males and the age groups of 30-39 to 40-49 years and 40-49 to 50-59 years in females. The fat mass ratio (fat mass/SMM) showed two peaks in both sexes (after the ages of 30 and 50 years in males and 40 and 50 years in females). A strong correlation was found between BMI and percentage of body fat (r = 0·823 in females v. r = 0·768 in males).

CONCLUSION

This is the first community-based study in the MENA region identifying sex- and age-stratified BC values using BIA. Our findings can be used as a reference for comparison in appropriate settings.

Predicting Breast Cancer Risk Using Radiomics Features of Mammography Images

Mammography images contain a lot of information about not only the mammary glands but also the skin, adipose tissue, and stroma, which may reflect the risk of developing breast cancer. We aimed to establish a method to predict breast cancer risk using radiomics features of mammography images and to enable further examinations and prophylactic treatment to reduce breast cancer mortality. We used mammography images of 4000 women with breast cancer and 1000 healthy women from the 'starting point set' of the OPTIMAM dataset, a public dataset. We trained a Light Gradient Boosting Machine using radiomics features extracted from mammography images of women with breast cancer (only the healthy side) and healthy women. This model was a binary classifier that could discriminate whether a given mammography image was of the contralateral side of women with breast cancer or not, and its performance was evaluated using five-fold cross-validation. The average area under the curve for five folds was 0.60122. Some radiomics features, such as 'wavelet-H_glcm_Correlation' and 'wavelet-H_firstorder_Maximum', showed distribution differences between the malignant and normal groups. Therefore, a single radiomics feature might reflect the breast cancer risk. The odds ratio of breast cancer incidence was 7.38 in women whose estimated malignancy probability was ≥0.95. Radiomics features from mammography images can help predict breast cancer risk.

Effect of long-term weight gain on the risk of breast cancer across women's whole adulthood as well as hormone-changed menopause stages: A systematic review and dose-response meta-analysis

Adult weight gain is a good indicator of excess body fatness for breast cancer risk. However, little is known about the effect of weight gain during other special periods in women's lifetime. A publication search in PubMed and Embase through April 2020 was conducted. A primary meta-analysis comparing the highest and lowest category and a secondary meta-analysis based on dose-response meta-analysis were performed to calculate risk estimates with 95% confidence intervals using a random-effects model. For postmenopausal breast cancer, the relative risk for highest vs. lowest category of adult weight gain and weight gain since menopause were 1.55 and 1.59 (RR = 1.55, 95% CI: 1.40, 1.71; RR = 1.59, 95% CI: 1.23, 2.05). For per 5 kg increase in adult weight gain, the summary RR of postmenopausal breast cancer was 1.08 (RR = 1.08, 95% CI: 1.07, 1.09), which is much stronger in Asian women (RR = 1.34, 95% CI: 1.22, 1.47). There was no significant finding among premenopausal women (RR = 1.00, 95% CI: 0.83, 1.21). Same as adult weight gain, weight gain since menopause might be an equivalent predictor for postmenopausal breast cancer risk. More studies are warranted to confirm the magnitude of this association further.

A review of nanotechnology-based approaches for breast cancer and triple-negative breast cancer

Breast cancer (BC) is one of the most prevalent cancers in women. Triple-negative breast cancer (TNBC) in which the three major receptors i.e. estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2), are absent is known to express the most aggressive phenotype and increased metastasis which results in the development of resistance to chemotherapy. It offers various therapeutic advantages in treating BC and TNBC. Nanotechnology offers various unique characteristics such as small size (nanometric), active and passive targeting, and the ability to attach multiple targeting moieties, controlled release, and site-specific targeting. This review focuses on conventional drug therapies, recent treatment strategies, and unique therapeutic approaches available for BC and TNBC. The role of breast cancer stem cells in the recurrence of BC and TNBC has also been highlighted. Several chemotherapeutic agents delivered using nanocarriers such as polymeric nanoparticles/micelles, metallic/inorganic NPs, and lipid-based NPs (Liposome, solid-lipid nanoparticles (SLNs), and nanostructured lipid carriers (NLCs)), etc. with excellent responses in the treatment of BC/TNBC along with breast cancer stem cells have been discussed in details. Moreover, the application of nanomedicine including CRISPR nanoparticle, exosomes for the treatment of BC/TNBC and other molecular targets available such as poly (ADP-ribose) polymerase (PARP), epidermal growth factor receptor (EGFR), Vascular endothelial growth factor (VEGF), etc. for further exploration have also been discussed.

The association between DXA-derived body fat measures and breast cancer risk among postmenopausal women in the Women's Health Initiative

Background

Most studies demonstrating an association between excess adiposity and postmenopausal breast cancer have used anthropometric measures, particularly body mass index (BMI). However, more direct body fat measures may more accurately determine the relationship between body fat distribution and breast cancer risk.

Methods

Cox proportional hazards regression models were created to examine the associations of dual‐energy x‐ray absorptiometry (DXA) body fat measures (at baseline and during follow‐up) with breast cancer risk among 10 931 postmenopausal women from the Women's Health Initiative cohort. A total of 639 incident invasive breast cancer cases (including 484 estrogen receptor positive (ER+) cases) were ascertained after a median follow‐up of 15.0 years.

Results

Excess whole body fat mass and trunk fat mass were positively associated with risk invasive breast cancer risk. These associations persisted even after additional adjustment for standard anthropometric measures. In time‐dependent analyses, we observed that both whole body fat mass and trunk fat mass, in the highest versus lowest category, were associated with a doubling of risk of invasive breast cancer overall (HR: 2.17; 95% CI: 1.54‐3.05 and 2.20; 1.55‐3.14, respectively) and of ER+ breast cancer (2.05; 1.37‐3.05 and 2.03; 1.34‐3.07, respectively). The remaining DXA measures were also positively associated with breast cancer risk in baseline and time‐dependent analyses.

Conclusion

These findings suggest that DXA‐derived body fat measures are positively associated with breast cancer risk after adjustment for BMI and other conventional breast cancer risk factors.

World Cancer Research Fund International: Continuous Update Project-systematic literature review and meta-analysis of observational cohort studies on physical activity, sedentary behavior, adiposity, and weight change and breast cancer risk

PURPOSE

The purpose of the present study was to systematically review the complex associations between energy balance-related factors and breast cancer risk, for which previous evidence has suggested different associations in the life course of women and by hormone receptor (HR) status of the tumor.

METHODS

Relevant publications on adulthood physical activity, sedentary behavior, body mass index (BMI), waist and hip circumferences, waist-to-hip ratio, and weight change and pre- and postmenopausal breast cancer risk were identified in PubMed up to 30 April 2017. Random-effects meta-analyses were conducted to summarize the relative risks across studies.

RESULTS

One hundred and twenty-six observational cohort studies comprising over 22,900 premenopausal and 103,000 postmenopausal breast cancer cases were meta-analyzed. Higher physical activity was inversely associated with both pre- and postmenopausal breast cancers, whereas increased sitting time was positively associated with postmenopausal breast cancer. Although higher early adult BMI (ages 18-30 years) was inversely associated with pre- and postmenopausal breast cancers, adult weight gain and greater body adiposity increased breast cancer risk in postmenopausal women, and the increased risk was evident for HR+ but not HR- breast cancers, and among never but not current users of postmenopausal hormones. The evidence was less consistent in premenopausal women. There were no associations with adult weight gain, inverse associations with adult BMI (study baseline) and hip circumference, and non-significant associations with waist circumference and waist-to-hip ratio that were reverted to positive associations on average in studies accounting for BMI. No significant associations were observed for HR-defined premenopausal breast cancers.

CONCLUSION

Better understanding on the impact of these factors on pre- and postmenopausal breast cancers and their subtypes along the life course is needed.

Vitamin D Controls Tumor Growth and CD8+ T Cell Infiltration in Breast Cancer

Women with low levels of vitamin D have a higher risk of developing breast cancer. Numerous studies associated the presence of a CD8+ T cell infiltration with a good prognosis. As vitamin D may play a key role in the modulation of the immune system, the objective of this work was to evaluate the impact of vitamin D on the breast cancer progression and mammary tumor microenvironment. We show that vitamin D decreases breast cancer tumor growth. Immunomonitoring of the different immune subsets in dissociated tumors revealed an increase in tumor infiltrating CD8+ T cells in the vitamin D-treated group. Interestingly, these CD8+ T cells exhibited a more active T cell (T_EM/CM) phenotype. However, in high-fat diet conditions, we observed an opposite effect of vitamin D on breast cancer tumor growth, associated with a reduction of CD8+ T cell infiltration. Our data show that vitamin D is able to modulate breast cancer tumor growth and inflammation in the tumor microenvironment in vivo. Unexpectedly, this effect is reversed in high-fat diet conditions, revealing the importance of diet on tumor growth. We believe that supplementation with vitamin D can in certain conditions represent a new adjuvant in the treatment of breast cancers.

Estrogens and breast cancer: Mechanisms involved in obesity-related development, growth and progression

Obesity is a risk factor for estrogen receptor-positive (ER+) breast cancer after menopause. The pro-proliferative effects of estrogens are well characterized and there is a growing body of evidence to also suggest an important role in tumorigenesis. Importantly, obesity not only increases the risk of breast cancer, but it also increases the risk of recurrence and cancer-associated death. Aromatase is the rate-limiting enzyme in estrogen biosynthesis and its expression in breast adipose stromal cells is hypothesized to drive the growth of breast tumors and confer resistance to endocrine therapy in obese postmenopausal women. The molecular regulation of aromatase has been characterized in response to many obesity-related molecules, including inflammatory mediators and adipokines. This review is aimed at providing an overview of our current knowledge in relation to the regulation of estrogens in adipose tissue and their role in driving breast tumor development, growth and progression.

The association between fat mass and the risk of breast cancer: A systematic review and meta-analysis

BACKGROUND & AIMS

Several cohort and case-control studies examined the association between fat mass (FM) and the risk of breast cancer; however, findings are conflicting. The purpose of the present study was to systematically review this association and conducted a meta-analysis, if possible.

METHOD

A systematic search of PubMed/Medline, Scopus, Web of Science and Embase databases was conducted for cohort and case-control studies, between January 2000 and 31 March 2018 with no language limitations. Multivariate adjusted relative risk (RR) estimates with 95% confidence intervals (CI) for each category of FM were pooled to examine the association.

RESULTS

Finally, 12 papers were considered for quantitative synthesis. The pooled RR for the highest vs. the lowest FM (%) of cohort studies was 1.44 (95% CI: 1.33, 1.56; I²: 63.3%, p = 0.008). The overall effect size for adjusted case-control studies showed no significant association (1.49, 95% CI: 0.77, 2.90; I²: 93.2%; p = 0.001). After stratification by menopause, it was revealed that the association between FM and the risk of breast cancer in post menopausal women (2.29, 95% CI: 1.12, 4.68; I²: 92%, p = 0.0001) was significant, while there was no significant association in pre-menopausal women (0.68, 95% CI: 0.18, 2.58; I²: 81.3%; p = 0.02).

CONCLUSION

Cohort studies showed that higher FM is positively associated with the risk for breast cancer. However, only case-control studies on post-menopausal women showed a positive link. Due to limited studies and high heterogeneity, findings should be interpreted with caution. More cohort studies are needed to clarify this association.

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.

Thyroid hormones and breast cancer association according to menopausal status and body mass index

BACKGROUND

Thyroxine (T4) has been positively associated with tumor cell proliferation, while the effect of triiodothyronine (T3) on cell proliferation has not been well-established because it differs according to the type of cell line used. In Mexico, it has been reported that 14.5% of adult women have some type of thyroid dysfunction and abnormalities in thyroid function tests have been observed in a variety of non-thyroidal illnesses, including breast cancer (BC). These abnormalities might change with body mass index (BMI) because thyroid hormones are involved in the regulation of various metabolic pathways and probably by menopausal status because obesity has been negatively associated with BC in premenopausal women and has been positively associated with BC in postmenopausal women.

METHODS

To assess the association between serum thyroid hormone concentration (T4 and T3) and BC and the influence of obesity as an effect modifier of this relationship in premenopausal and postmenopausal women, we measured serum thyroid hormone and thyroid antibody levels in 682 patients with incident breast cancer (cases) and 731 controls, who participated in a population-based case-control study performed from 2004 to 2007 in three states of Mexico. We tested the association of total T4 (TT4) and total T3 (TT3) stratifying by menopausal status and body mass index (BMI), and adjusted for other health and demographic risk factors using logistic regressions models.

RESULTS

Higher serum total T4 (TT4) concentrations were associated with BC in both premenopausal (odds ratio (OR) per standard deviation = 5.98, 95% CI 3.01-11.90) and postmenopausal women (OR per standard deviation = 2.81, 95% CI 2.17-3.65). In premenopausal women, the effect of TT4 decreased as BMI increased while the opposite was observed in postmenopausal women. The significance of the effect modification was marginal (p = 0.059) in postmenopausal women and was not significant in premenopausal women (p = 0.22). Lower TT3 concentrations were associated with BC in both premenopausal and postmenopausal women and no effect modification was observed.

CONCLUSIONS

There is a strong association between BC and serum concentrations of TT3 and TT4; this needs to be further investigated to understand why it happens and how important it is to consider these alterations in treatment.

Parity, weight change, and maternal risk of cardiovascular events

BACKGROUND

High parity has been suggested to increase risk of maternal cardiovascular disease independent of body mass index measured after childbearing. Pregnancy is, however, associated with persistent weight gain and metabolic changes that, independent of parity, increase the risk of cardiovascular disease. It could therefore be questioned if high parity independently increases the risk of cardiovascular disease or if this association may be confounded, mediated, or modified by other parity-related factors.

OBJECTIVE

We sought to investigate the association between parity and risk of cardiovascular disease, and secondary outcomes in terms of myocardial infarction and cerebral infarction, with particular focus on potential mediation by anthropometric measures and effect modification by lactation.

STUDY DESIGN

We used data from 16,515 female participants (age 44.5-73.6 years) of the population-based Malmö Diet and Cancer Study with baseline examination from 1991 through 1996. The Malmö Diet and Cancer Study was followed up throughout 2010, with a median follow-up of 15.8 years. We used Cox proportional hazards model to examine the association between parity and cardiovascular disease.

RESULTS

Adjusted for age and other potential confounders, grand multiparous women (≥5 children) had an increased risk of cardiovascular disease (hazard ratio, 1.60; 95% confidence interval, 1.20-2.14), myocardial infarction (hazard ratio, 1.68; 95% confidence interval, 1.15-2.45), and cerebral infarction (hazard ratio, 1.74; 95% confidence interval, 1.18-2.58) compared to women with 2 children. Additional adjustment for baseline body mass index and weight change since age 20 years attenuated the risk, but the increased risk for cardiovascular disease (hazard ratio, 1.38; 95% confidence interval, 1.02-1.87) and myocardial infarction (hazard ratio, 1.53; 95% confidence interval, 1.04-2.26) in grand multiparous women remained significant. Models stratified by lactation time showed that risk was only raised in grand multiparous women who had a mean lactation time of <4 mo/child. In sensitivity analyses excluding women with a history of diabetes at baseline, risk estimates for grand multiparous women became nonsignificant in the full model.

CONCLUSION

Part of the increased risk of cardiovascular disease and myocardial infarction in grand multiparous women seems to be mediated by weight gain and potentially by higher likelihood of type 2 diabetes mellitus. Lactation may modify the increased risk of grand multiparity in that longer duration might offset the cardiovascular disease risk.

Central obesity and risks of pre- and postmenopausal breast cancer: a dose-response meta-analysis of prospective studies

Epidemiologic evidence has shown inconsistent findings regarding the relationships between abdominal fatness, as measured by waist circumferences (WC) or waist-to-hip ratio (WHR), and risks of pre- and postmenopausal breast cancer (BC). A dose-response meta-analysis of prospective studies was conducted to address these issues. Potentially eligible studies were identified by searching PubMed and EMBASE databases, and by carefully reviewing the bibliographies of retrieved publications and related reviews. The summary relative risks (RRs) with 95% confidence intervals (CIs) were calculated using a random-effects model. When the most fully adjusted RRs were combined, both WC (14 studies, RR _{per 10-cm increase}  = 1.06, 95% CI: 1.04-1.09, I²  = 29.9%) and WHR (15 studies, RR _{per 0.1-unit increase}  = 1.07, 95% CI: 1.01-1.14, I²  = 52.9%) were significantly positively associated with postmenopausal BC, but neither WC (eight studies, RR _{per 10-cm increase}  = 1.05, 95% CI: 0.99-1.10, I²  = 0%) nor WHR (11 studies, RR _{per 0.1-unit increase}  = 1.07, 95% CI: 0.95-1.21, I²  = 59.7%) were associated with premenopausal BC. The WHR-postmenopausal BC association lost statistical significance after correcting publication bias (RR _{per 0.1-unit increase}  = 1.06, 95% CI: 0.99-1.13). When considering BMI-adjusted RRs, WC was associated with both pre- (five studies, RR _{per 10-cm increase}  = 1.09, 95% CI: 1.02-1.16, I²  = 0%) and postmenopausal BC (seven studies, RR _{per 10-cm increase}  = 1.05, 95% CI: 1.02-1.08, I²  = 6.3%), whereas WHR was not associated with either pre- (seven studies, RR _{per 0.1-unit increase}  = 1.12, 95% CI: 0.94-1.34, I²  = 70.9%) or postmenopausal BC (eight studies, RR _{per 0.1-unit increase}  = 1.05, 95% CI: 0.98-1.13, I²  = 57.3%). Among non-current (former or never) users of hormone replacement therapy, the summary RR _{per 10-cm increase} of postmenopausal BC associated with WC was 1.08 (95% CI: 1.03-1.05, I²  = 69.2%, seven studies; BMI-adjusted RR = 1.05, 95% CI: 1.02-1.09, I²  = 22.8%, four studies). This meta-analysis indicates that central obesity measured by WC, but not by WHR, is associated with modestly increased risks of both pre- and postmenopausal BC independent of general obesity.

Low-Grade Inflammation, Oxidative Stress and Risk of Invasive Post-Menopausal Breast Cancer - A Nested Case-Control Study from the Malmö Diet and Cancer Cohort

OBJECTIVE

Although cancer promotes inflammation, the role of inflammation in tumor-genesis is less well established. The aim was to examine if low-grade inflammation is related to post-menopausal breast cancer risk, and if obesity modifies this association.

METHODS

In the Malmö Diet and Cancer cohort, a nested case-control study was defined among 8,513 women free of cancer and aged 55-73 years at baseline (1991-96); 459 were diagnosed with invasive breast cancer during follow-up (until December 31st, 2010). In laboratory analyses of blood from 446 cases, and 885 controls (matched on age and date of blood sampling) we examined systemic inflammation markers: oxidized (ox)-LDL, interleukin (IL)-1β, IL-6, IL-8, tumor necrosis factor (TNF)-α, white blood cells, lymphocytes and neutrophils. Odds ratios (OR) and 95% confidence intervals (CI) for breast cancer risk was calculated using multivariable conditional logistic regression.

RESULTS

Inverse associations with breast cancer were seen in fully-adjusted models, for 2nd and 3rd tertiles of ox-LDL, OR (95% CI): 0.65 (0.47-0.90), 0.63 (0.45-0.89) respectively, p-trend = 0.01; and for the 3rd tertile of TNF-α, 0.65 (0.43-0.99), p-trend = 0.04. In contrast, those in the highest IL-1β category had higher risk, 1.71 (1.05-2.79), p-trend = 0.01. Obesity did not modify associations between inflammation biomarkers and breast cancer.

CONCLUSION

Our study does not suggest that low-grade inflammation increase the risk of post-menopausal breast cancer.

Association between breast cancer, breast density, and body adiposity evaluated by MRI

OBJECTIVE

Despite the lack of reliable methods with which to measure breast density from 2D mammograms, numerous studies have demonstrated a positive association between breast cancer and breast density. The goal of this study was to study the association between breast cancer and body adiposity, as well as breast density quantitatively assessed from 3D MRI breast images.

METHODS

Breast density was calculated from 3D T1-weighted MRI images. The thickness of the upper abdominal adipose layer was used as a surrogate marker for body adiposity. We evaluated the correlation between breast density, age, body adiposity, and breast cancer.

RESULTS

Breast density was calculated for 410 patients with unilateral invasive breast cancer, 73 patients with ductal carcinoma in situ (DCIS), and 361 controls without breast cancer. Breast density was inversely related to age and the thickness of the upper abdominal adipose layer. Breast cancer was only positively associated with body adiposity and age.

CONCLUSION

Age and body adiposity are predictive of breast density. Breast cancer was not associated with breast density; however, it was associated with the thickness of the upper abdominal adipose layer, a surrogate marker for body adiposity. Our results based on a limited number of patients warrant further investigations.

KEY POINTS

• MRI breast density is negatively associated with body adiposity. • MRI breast density is negatively associated with age. • Breast cancer is positively associated with body adiposity. • Breast Cancer is not associated with MRI breast density.

Obesity in breast cancer--what is the risk factor?

Environmental factors influence breast cancer incidence and progression. High body mass index (BMI) is associated with increased risk of post-menopausal breast cancer and with poorer outcome in those with a history of breast cancer. High BMI is generally interpreted as excess adiposity (overweight or obesity) and the World Cancer Research Fund judged that the associations between BMI and incidence of breast cancer were due to body fatness. Although BMI is the most common measure used to characterise body composition, it cannot distinguish lean mass from fat mass, or characterise body fat distribution, and so individuals with the same BMI can have different body composition. In particular, the relation between BMI and lean or fat mass may differ between people with or without disease. The question therefore arises as to what aspect or aspects of body composition are causally linked to the poorer outcome of breast cancer patients with high BMI. This question is not addressed in the literature. Most studies have used BMI, without discussion of its shortcomings as a marker of body composition, leading to potentially important misinterpretation. In this article we review the different measurements used to characterise body composition in the literature, and how they relate to breast cancer risk and prognosis. Further research is required to better characterise the relation of body composition to breast cancer.

Influence of age and gender on fat mass, fat-free mass and skeletal muscle mass among Australian adults: the Australian diabetes, obesity and lifestyle study (AusDiab)

BACKGROUND

Bioelectrical impedance (BIA) represents a simple, inexpensive and non-invasive method that is often used to assess fat-mass (FM) and fat-free mass (FFM) in large population-based cohorts.

OBJECTIVE

The aim of this study was to describe the reference ranges and examine the influence of age and gender on FM, FFM and skeletal muscle mass (SMM) as well as height-adjusted estimates of FM [fat mass index (FMI)], FFM [fat-free mass index (FFMI)] and SMM [SMM index (SMI)] in a national, population-based cohort of Australian adults.

DESIGN AND PARTICIPANTS

The analytical sample included a total of 8,582 adults aged 25-91 years of Europid origin with complete data involved in the cross-sectional 1999-2000 Australian, Diabetes, Obesity and Lifestyle (AusDiab) Study.

MEASUREMENTS

Bioelectrical impedance analysis was used to examine components of body composition. Demographic information was derived from a household interview.

RESULTS

For both genders, FFM, SMM and SMI decreased linearly from the age of 25 years, with the exception that in men SMI was not related to age and FFM peaked at age 38 years before declining thereafter. The relative loss from peak values to ≥75 years in FFM (6-8%) and SMM (11-15%) was similar between men and women. For FM and FMI, there was a curvilinear relationship with age in both genders, but peak values were detected 6-7 years later in women with a similar relative loss thereafter. For FFMI there was no change with age in men and a modest increase in women.

CONCLUSION

In Australian adults there is heterogeneity in the age of onset, pattern and magnitude of changes in the different measures of muscle and fat mass derived from BIA, but overall the age-related losses were similar between men and women.

[Level of physical activity in the prevention of excess visceral fat in postmenopausal women: how much is needed?]

OBJECTIVE

To analyze the level of physical activity (kcal/week) needed to prevent excess visceral fat in postmenopausal women.

SUBJECTS AND METHODS

The sample included 239 women with a mean age of 57.2 years. Visceral fat area (VFA) was measured by octopolar bioelectrical impedance, and physical activity, by the long version IPAQ. ROC Curves (Receiver Operating Characteristic) were drawn, and a 95% confidence interval was used.

RESULTS

The areas under the ROC curve for moderate physical activity and walk proved to be significant. Weekly expenditure of 1,601 kcal in walking, or 2,283 kcal in moderate physical activity were identified as good cutoff values to prevent excess VFA.

CONCLUSION

Mild to moderate physical activity, with a caloric expenditure between 1,601 and 2,283 kcal/week, prevents excess central adiposity in postmenopausal women.

Cohort study of risk factors for breast cancer in post menopausal women

OBJECTIVES

The present study assessed more than 800 potential risk factors to identify new predictors of breast cancer and compare the independence and relative importance of established risk factors.

METHODS

Data were collected by the Women's Health Initiative and included 147,202 women ages 50 to 79 who were enrolled from 1993 to 1998 and followed for 8 years. Analyses performed in 2011 and 2012 used the Cox proportional hazard regression to test the association between more than 800 baseline risk factors and incident breast cancer.

RESULTS

Baseline factors independently associated with subsequent breast cancer at the p<0.001 level (in decreasing order of statistical significance) were breast aspiration, family history, age, weight, history of breast biopsies, estrogen and progestin use, fewer live births, greater age at menopause, history of thyroid cancer, breast tenderness, digitalis use, alcohol intake, white race, not restless, no vaginal dryness, relative with prostate cancer, colon polyps, smoking, no breast augmentation, and no osteoporosis. Risk factors previously reported that were not independently associated with breast cancer in the present study included socioeconomic status, months of breast feeding, age at first birth, adiposity measures, adult weight gain, timing of initiation of hormone therapy, and several dietary, psychological, and exercise variables. Family history was not found to alter the risk associated with other factors.

CONCLUSIONS

These results suggest that some risk factors not commonly studied may be important for breast cancer and some frequently cited risk factors may be relatively unimportant or secondary.

Body fat and breast cancer risk in postmenopausal women: a longitudinal study

Associations between anthropometric indices of obesity and breast cancer risk may fail to capture the true relationship between excess body fat and risk. We used dual-energy-X-ray-absorptiometry- (DXA-) derived measures of body fat obtained in the Women's Health Initiative to examine the association between body fat and breast cancer risk; we compared these risk estimates with those for conventional anthropometric measurements. The study included 10,960 postmenopausal women aged 50–79 years at recruitment, with baseline DXA measurements and no history of breast cancer. During followup (median: 12.9 years), 503 incident breast cancer cases were diagnosed. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated using Cox proportional hazards models. All baseline DXA-derived body fat measures showed strong positive associations with breast cancer risk. The multivariable-adjusted HR for the uppermost quintile level (versus lowest) ranged from 1.53 (95% CI 1.14–2.07) for fat mass of the right leg to 2.05 (1.50–2.79) for fat mass of the trunk. Anthropometric indices (categorized by quintiles) of obesity (BMI (1.97, 1.45–2.68), waist circumference (1.97, 1.46–2.65), and waist : hip ratio (1.91, 1.41–2.58)) were all strongly, positively associated with risk and did not differ from DXA-derived measures in prediction of risk.

Exposures to synthetic estrogens at different times during the life, and their effect on breast cancer risk

Women are using estrogens for many purposes, such as to prevent pregnancy or miscarriage, or to treat menopausal symptoms. Estrogens also have been used to treat breast cancer which seems puzzling, since there is convincing evidence to support a link between high lifetime estrogen exposure and increased breast cancer risk. In this review, we discuss the findings that maternal exposure to the synthetic estrogen diethylstilbestrol during pregnancy increases breast cancer risk in both exposed mothers and their daughters. In addition, we review data regarding the use of estrogens in oral contraceptives and as postmenopausal hormone therapy and discuss the opposing effects on breast cancer risk based upon timing of exposure. We place particular emphasis on studies investigating how maternal estrogenic exposures during pregnancy increase breast cancer risk among daughters. New data suggest that these exposures induce epigenetic modifications in the mammary gland and germ cells, thereby causing an inheritable increase in breast cancer risk for multiple generations.

Progesterone--promoter or inhibitor of breast cancer

Based on the results of a French cohort of postmenopausal women, it has been claimed that micronized progesterone does not enhance breast cancer risk. The impact of reproductive factors on breast cancer risk and a high prevalence of occult breast carcinomas at the time of menopause suggest an involvement of endogenous progesterone in the development of breast cancer. High mammographic density in the luteal phase and during treatment with estrogen/progestogen combinations reflect a change in the composition of mammary stroma and an increased water accumulation in the extracellular matrix which is caused by hygroscopic hyaluronan-proteoglycan aggregates. Proteoglycans are also involved in the regulation of proliferation, migration, and differentiation of epithelial cells and angiogenesis, and may influence malignant transformation of breast cells and progression of tumors. Reports on a lack of effect of estrogen/progesterone therapy on breast cancer risk may be rooted in a selective prescription to overweight women and/or to the very low progesterone serum levels after oral administration owing to a strong inactivation rate. The contradictory results concerning the proliferative effect of progesterone may be associated with a different local metabolism in normal compared to malignant breast tissue. Similar to other progestogens, hormone replacement therapy with progesterone seems to promote the development of breast cancer, provided that the progesterone serum levels have reached the threshold for endometrial protection.

Interaction between smoking and obesity and the risk of developing breast cancer among postmenopausal women: the Women's Health Initiative Observational Study

Obesity is a well-established risk factor for postmenopausal breast cancer. Recent studies suggest that smoking increases the risk of breast cancer. However, the effect of co-occurrence of smoking and obesity on breast cancer risk remains unclear. A total of 76,628 women aged 50-79 years enrolled in the Women's Health Initiative Observational Study were followed through August 14, 2009. Cox proportional hazards regression models were used to estimate hazard ratios and 95% confidence intervals. Over an average 10.3 years of follow-up, 3,378 incident cases of invasive breast cancer were identified. The effect of smoking on the risk of developing invasive breast cancer was modified significantly by obesity status among postmenopausal women, regardless of whether the obesity status was defined by body mass index (P(interaction) = 0.01) or waist circumference (P(interaction) = 0.02). A significant association between smoking and breast cancer risk was noted in nonobese women (hazard ratio = 1.25, 95% confidence interval: 1.05, 1.47) but not in obese women (hazard ratio = 0.96, 95% confidence interval: 0.69, 1.34). In conclusion, this study suggests that the effect of smoking exposure on breast cancer risk was modified by obesity among postmenopausal women. The modification effect did not differ by general versus abdominal obesity.

Association between body mass index and risk of breast cancer in Tunisian women

BACKGROUND AND OBJECTIVES

The number of breast cancer in women has increased dramatically in Tunisia. The cause is perceived to stem from adaptation to a westernized life style which increases body mass index (BMI). This study aimed to investigate the association between BMI and breast cancer among Tunisian women.

DESIGN AND SETTING

Hospital-based case control study of breast cancer patients seen between November 2006 and April 2009 at the University College Hospital Farhat Hached in Sousse, Tunisia.

PATIENTS AND METHODS

Standardized questionnaires concerning BMI and other anthropometric data were completed on 400 breast cancer cases and 400 controls. The controls were frequency-matched to the cases by age.

RESULTS

BMI at diagnosis was positively correlated with the risk of breast cancer among postmenopausal women (P<.001 for trend). When compared with women with a low BMI (<19), women with a BMI of 23-27 and 27-31 had a 1.7-fold (95% CI, 1.1-2.9) and 2.1-fold (95% CI, 1.1-3.9) increased risk of breast cancer, respectively, after adjustment for non-anthropometric risk factors. BMI at diagnosis was not related to the risk of breast cancer among premenopausal women. The odds ratios for premenopausal women with a BMI of 23-27 and 27-31 were 1.5 (95% CI, 0.8-2.8) and 1.3 (95% CI, 0.4-4.5), respectively. Furthermore, present BMI was not associated with breast cancer risk in either pre- and postmenopausal women.

CONCLUSIONS

Weight control in obese women may be an effective measure of breast cancer prevention in postmenopausal women.

Are neighborhood education levels associated with BMI among adults in Cairo, Egypt?

This study examined the association between area-level education and BMI among adults in Cairo, Egypt. A sample of 3993 households including 1990 men and 2003 women were analyzed from the 2007 Cairo Urban Inequity Study, a study which aimed to identify potential intra-urban inequities in health related to the environment and living conditions in Cairo. Using multilevel analysis, we found that residents of high education neighborhoods were significantly less likely to be obese compared to low education neighborhoods. An inverse association between neighborhood education and individual BMI was observed whereby each unit increase in percentage of households with greater than a high school education was associated with a 0.036 kg/m(2) decrease in BMI of individuals. This translated into a difference between high and low education neighborhoods of 6.86 kg (15.1 lb) for women based on an average height of 1.65 m and 6.10 kg (13.4 lb) for men based on an average height of 1.75 m after adjusting for sociodemographic, socioeconomic, health and environmental factors. These findings suggest that programs aiming to reduce BMI among adults in this setting may be well-served by focusing on education since it appears to have an effect at the neighborhood level over and above the impact it has at the individual level. This may be due to several factors such as greater access to knowledge and information regarding health and nutrition, greater food availability, and shifting cultural perceptions of beauty away from an ideal body shape of plumpness in favor of thinness in high education neighborhoods. The cross-sectional nature of our study does not allow for causal interpretations, however, so further studies exploring why the neighborhood education-BMI association is so significant is warranted.

Body fat distribution and risk of premenopausal breast cancer in the Nurses' Health Study II

Body mass index is inversely associated with risk of premenopausal breast cancer, but the underlying mechanisms for this association are poorly understood. Abdominal adiposity is associated with metabolic and hormonal changes, many of which have been associated with the risk of premenopausal breast cancer. We investigated the association between body fat distribution, assessed in 1993 by self-reported waist circumference, hip circumference, and waist to hip ratio, and the incidence of premenopausal breast cancer in the Nurses' Health Study II. Cox proportional hazards regression models were used to calculate hazard ratios and 95% confidence intervals (CIs). Statistical tests were two-sided. During 426,164 person-years of follow-up from 1993 to 2005, 620 cases of breast cancer were diagnosed among 45,799 women. Hormone receptor status information was available for 84% of the breast cancers. The age-standardized incidence rates of breast cancer were 131 per 100,000 person-years among those in the lowest quintile of waist circumference and 136 per 100,000 person-years among those in the highest quintile. No statistically significant associations were found between waist circumference, hip circumference, or the waist to hip ratio and risk of breast cancer. However, each of the three body fat distribution measures was statistically significantly associated with greater incidence of estrogen receptor (ER)-negative breast cancer. The multivariable-adjusted hazard ratios of ER-negative breast cancer for the highest vs the lowest quintile of each body fat distribution measure were 2.75 (95% CI = 1.15 to 6.54; P(trend) = .05) for waist circumference, 2.40 (95% CI = 0.95 to 6.08; P(trend) = .26) for hip circumference, and 1.95 (95% CI = 1.10 to 3.46; P(trend) = .01) for waist to hip ratio. Our findings suggest that body fat distribution does not play an important role in the overall incidence of premenopausal breast cancer but is associated with an increased risk for ER-negative breast cancer.

Adiposity changes after a 1-year aerobic exercise intervention among postmenopausal women: a randomized controlled trial

Objective:

We examined the effects of an aerobic exercise intervention on adiposity outcomes that may be involved in the association between physical activity and breast cancer risk.

Design:

This study was a two-centre, two-armed, randomized controlled trial. The 1-year-long exercise intervention included 45 min of moderate-to-vigorous aerobic exercise five times per week, with at least three of the sessions being facility based. The control group was asked not to change their activity and both groups were asked not to change their diet.

Subjects:

A total of 320 postmenopausal, sedentary, normal weight-to-obese women aged 50–74 years who were cancer-free, nondiabetic and nonhormone replacement therapy users were included in this study.

Measurements:

Anthropometric measurements of height, weight and waist and hip circumferences; dual energy X-ray absorptiometry measurements of total body fat; and computerized tomography measurements of abdominal adiposity were carried out.

Results:

Women in the exercise group exercised a mean of 3.6 days (s.d.=1.3) per week and 178.5 min (s.d.=76.1) per week. Changes in all measures of adiposity favored exercisers relative to controls (P<0.001). The mean difference between groups was: −1.8 kg for body weight; −2.0 kg for total body fat; −14.9 cm² for intra-abdominal fat area; and −24.1 cm² for subcutaneous abdominal fat area. A linear trend of greater body fat loss with increasing volume of exercise was also observed.

Conclusion:

A 1-year aerobic exercise program consistent with current public health guidelines resulted in reduced adiposity levels in previously sedentary postmenopausal women at higher risk of breast cancer.

A case-control study of body mass index and breast cancer risk in white and African-American women

OBJECTIVE

Large body size has been associated with decreased risk of breast cancer in premenopausal women but with increased risk in postmenopausal women. Limited information is available about African-American women and differences by estrogen and progesterone receptor status.

METHODS

We analyzed data from the Women's Contraceptive and Reproductive Experiences Study among 3,997 white and African-American breast cancer case patients diagnosed in 1994 to 1998 and 4,041 control participants ages 35 to 64 years. We calculated multivariate odds ratios (OR) as measures of relative risk of breast cancer associated with self-reported body mass index (BMI) at age 18 and 5 years before diagnosis (recent BMI).

RESULTS

Risk tended to decrease with increasing BMI at age 18 years in all women [OR(BMI > or = 25 kg/m(2) versus < 20 kg/m(2)) = 0.76; 95% confidence interval (CI), 0.63-0.90; P(trend) = 0.005] and with recent BMI in premenopausal women (OR(BMI > or = 35 kg/m(2) versus < 25 kg/m(2)) = 0.81; 95% CI, 0.61-1.06; P(trend) = 0.05), unmodified by race. Among postmenopausal white but not African-American women, there was an inverse relation between recent BMI and risk. High recent BMI was associated with increased risk of estrogen receptor- and progesterone receptor-positive tumors among postmenopausal African-American women (OR(BMI > or = 35 kg/m(2) versus < 25 kg/m(2)) = 1.83; 95% CI, 1.08-3.09; P(trend) = 0.03).

CONCLUSION

Among women at age 35 to 64 years, BMI at age 18 years is inversely associated with risk of breast cancer, but association with recent BMI varies by menopause status, race, and hormone receptor status.

IMPACT

Our findings indicate that studies of BMI and breast cancer should consider breast cancer subtypes.

Accuracy of body mass index to determine obesity in women with breast cancer: an observational study of Taiwanese sample

BACKGROUND

Obesity is common in women with breast cancer. The risk of obesity-induced metabolic syndrome is higher in Asians than in Caucasians. Excessive body fat accumulation has been associated with a worse prognosis. However, the most popular clinical indicator of obesity is not fat itself, but body mass index (BMI).

OBJECTIVES

The purposes of this study were to determine the consistency of BMI and body fat percentage (BF%) in determining obesity and to identify the best BMI cutoffs for identifying obesity in Taiwanese women with breast cancer.

METHODS

Body fat and fat-free mass were measured by bioelectrical impedance 1 day before breast surgery for 200 women with breast cancer. BMI was calculated as weight (in kilograms) divided by height (in meters) squared.

RESULTS

BMI and BF% were highly correlated (r=0.91; p<0.001). However, BMI exhibited poor sensitivity for identifying obesity (47%). The sensitivity of BMI to detect obesity was better in women over age 60. The best BMI cutoff for obesity was 22.3 kg/m2 with a sensitivity and specificity of 89% (95% CI=83-94%) and 87% (95% CI=77-93%) respectively, and the total accuracy rate improved from 65% to 89%.

CONCLUSIONS

Using BMI to identify obesity in Taiwanese women with breast cancer requires careful attention to the diagnostic criterion chosen. The World Health Organization criterion tends to underestimate the prevalence of obesity, especially for younger women with breast cancer (under age 40).

Effect of Obesity on Breast Cancer Development

In recent years, obesity has been identified as a risk factor for the development of breast cancer in postmenopausal women, and it has been associated with a poor outcome. Many factors appear to be important in the mechanism of this increased risk, including estrogen, estrogen receptors, and the adipokines leptin and adiponectin. Estrogen, a potent mitogen for mammary cells, has long been implicated in the development of mammary tumors. Because adipose-associated aromatase activity increases the conversion of androgen to estrogen, mammary adipose tissue is thought to be an important source of local estrogen production. Leptin, which increases in the circulation in proportion to body fat stores, has been demonstrated in vitro to promote breast cancer cell growth. Animal models have also identified leptin as an important factor for the development of mammary tumors. In contrast to leptin, serum adiponectin concentrations are inversely related to body fat stores, and the addition of adiponectin to human breast cancer cells reduces cell proliferation and enhances apoptosis. This review explores the relationship between these factors and the development of mammary cancer in humans and mouse models.

Screening and prevention of breast cancer in primary care

Mammography remains the mainstay of breast cancer screening. There is little controversy that mammography reduces the risk of dying from breast cancer by about 23% among women between the ages of 50 and 69 years, although the harms associated with false-positive results and overdiagnosis limit the net benefit of mammography. Women in their 70s may have a small benefit from screening mammography, but overdiagnosis increases in this age group as do competing causes of death. While new data support a 16% reduction in breast cancer mortality for 40- to 49-year-old women after 10 years of screening, the net benefit is less compelling in part because of the lower incidence of breast cancer in this age group and because mammography is less sensitive and specific in women younger than 50 years. Digital mammography is more sensitive than film mammography in young women with similar specificity, but no improvements in breast cancer outcomes have been demonstrated. Magnetic resonance imaging may benefit the highest risk women. Randomized trials suggest that self-breast examination does more harm than good. Primary prevention with currently approved medications will have a negligible effect on breast cancer incidence. Public health efforts aimed at increasing mammography screening rates, promoting regular exercise in all women, maintaining a healthy weight, limiting alcohol intake, and limiting postmenopausal hormone therapy may help to continue the recent trend of lower breast cancer incidence and mortality among American women.

Minireview: Obesity and breast cancer: the estrogen connection

There is now substantial evidence that overweight and/or obesity and/or weight gain are risk factors for the development of postmenopausal breast cancer. In addition, obesity and/or elevated body mass index at breast cancer diagnosis has a negative impact on prognosis for both premenopausal and postmenopausal women. Therefore, understanding the mechanism of how obesity affects the mammary tumorigenesis process is an important health issue. Elevated serum estrogen levels as well as enhanced local production of estrogen have been considered primary mediators of how increased body weight promotes breast cancer development in postmenopausal women. Here, we provide an overview of estrogen's relationship with both obesity and breast cancer as separate entities. Human and relevant preclinical studies are cited. In addition, other growth factors that may be involved in this relationship are considered.

Physical activity, weight control, and breast cancer risk and survival: clinical trial rationale and design considerations

Substantial observational epidemiological evidence exists that physical activity and weight control are associated with decreased risk of postmenopausal breast cancer. Uncertainty remains regarding several aspects of these associations, including the effect of possible confounding factors on these associations. We present the rationale and design for two randomized controlled trials that can help resolve this uncertainty. In a 5-year prevention trial conducted among women at high risk of breast cancer, the primary endpoint would be breast cancer incidence. For a comparable survivorship trial, the primary endpoint would be the disease-free interval and secondary endpoints would be breast cancer recurrence-free interval, second primary breast cancer, and total invasive plus in situ breast cancer. A set of inclusion and exclusion criteria is proposed for both trials. Intervention goals are the same for both trials. Goals for the weight control intervention would be, for women whose body mass index (BMI) is greater than 25 kg/m(2), to lose 10% of body weight and, for women whose BMI is less than or equal to 25 kg/m(2), to avoid weight gain. The goal for the physical activity intervention would be to achieve and maintain regular participation in a moderate-intensity physical activity program for a total of 150-225 minutes over at least 5 days per week. Sample size calculations are based on alternative assumptions about hazard ratio, adherence, follow-up duration, and power and are presented for the primary prevention and survivorship trials. Although both studies could enhance our understanding of breast cancer etiology and benefit public health, practical considerations, including smaller sample size, ease of recruitment, and reduced likelihood of early termination, favor the survivorship trial at this time.

Energy balance, physical activity, and cancer risk

This chapter posits that cancer is a complex and multifactorial process as demonstrated by the expression and production of key endocrine and steroid hormones that intermesh with lifestyle factors (physical activity, body size, and diet) in combination to heighten cancer risk. Excess weight has been associated with increased mortality from all cancers combined and for cancers of several specific sites. The prevalence of obesity has reached epidemic levels in many parts of the world; more than 1 billion adults are overweight with a body mass index (BMI) exceeding 25. Overweight and obesity are clinically defined indicators of a disease process characterized by the accumulation of body fat due to an excess of energy intake (nutritional intake) relative to energy expenditure (physical activity). When energy intake exceeds energy expenditure over a prolonged period of time, the result is a positive energy balance (PEB), which leads to the development of obesity. This physical state is ideal for intervention and can be modulated by changes in energy intake, expenditure, or both. Nutritional intake is a modifiable factor in the energy balance-cancer linkage primarily tested by caloric restriction studies in animals and the effect of energy availability. Restriction of calories by 10 to 40% has been shown to decrease cell proliferation, increasing apoptosis through anti-angiogenic processes. The potent anticancer effect of caloric restriction is clear, but caloric restriction alone is not generally considered to be a feasible strategy for cancer prevention in humans. Identification and development of preventive strategies that "mimic" the anticancer effects of low energy intake are desirable. The independent effect of energy intake on cancer risk has been difficult to estimate because body size and physical activity are strong determinants of total energy expenditure. The mechanisms that account for the inhibitory effects of physical activity on the carcinogenic process are reduction in fat stores, activity related changes in sex-hormone levels, altered immune function, effects in insulin and insulin-like growth factors, reduced free radical generation, and direct effect on the tumor. Epidemiologic evidence posits that the cascade of actions linking overweight and obesity to carcinogenesis are triggered by the endocrine and metabolic system. Perturbations to these systems result in the alterations in the levels of bioavailable growth factors, steroid hormones, and inflammatory markers. Elevated serum concentrations of insulin lead to a state of hyperinsulinemia. This physiological state causes a reduction in insulin-like growth factor-binding proteins and promotes the synthesis and biological activity of insulin-like growth factor (IGF)-I, which regulates cellular growth in response to available energy and nutrients from diet and body reserves. In vitro studies have clearly established that both insulin and IGF-I act as growth factors that promote cell proliferation and inhibit apoptosis. Insulin also affects on the synthesis and biological availability of the male and female sex steroids, including androgens, progesterone, and estrogens. Experimental and clinical evidence also indicates a central role of estrogens and progesterone in regulating cellular differentiation, proliferation, and apoptosis induction. Hyperinsulinemia is also associated with alterations in molecular systems such as endogenous hormones and adipokines that regulate inflammatory responses. Obesity-related dysregulation of adipokines has the ability to contribute to tumorigenesis and tumor invasion via metastatic potential. Given the substantial level of weight gain in industrialized countries in the last two decades, there is great interest in understanding all of the mechanisms by which obesity contributes to the carcinogenic process. Continued focus must be directed to understanding the various relationships between specific nutrients and dietary components and cancer cause and prevention. A reductionist approach is not sufficient for the basic biological mechanisms underlying the effect of diet and physical activity on cancer. The joint association between energy balance and cancer risk are hypothesized to share the same underlying mechanisms, the amplification of chemical mediators that modulate cancer risk depending on the responsiveness to those hormones to the target tissue of interest. Disentangling the connection between obesity, the insulin-IGF axis, endogenous hormones, inflammatory markers, and their molecular interaction is vital.

Weight, height, body mass index and risk of breast cancer in postmenopausal women: a case-control study

Background

Many women in Iran have a relatively high body mass index. To investigate whether the condition contributes to excess breast cancer cases, a case-control study was conducted to assess the relationships between anthropometric variables and breast cancer risk in Tehran, Iran.

Methods

All incident cases of breast cancer in the Iranian Centre for Breast Cancer (ICBC) were identified through the case records. Eligible cases were all postmenopausal women with histological confirmed diagnosis of breast cancer during 1996 to year 2000. Controls were randomly selected postmenopausal women attending the ICBC for clinical breast examination during the same period. The body mass index (BMI) was calculated based on weights and heights as measured by the ICBC nursing staff. Both tests for trend and logistic regression analysis were performed to calculate odds ratios and 95% confidence intervals as measures of relative risk.

Results

In all, 116 breast cancer cases and 116 controls were studied. There were no significant differences between cases and control with regard to most independent variables studied. However, a significant difference was observed between cases and controls indicating that the mean BMI was higher in cases as compared to controls (P = 0.004). Performing logistic regression analysis while controlling for age, age at menopause, family history of breast cancer and parity, the results showed that women with a BMI in the obese range had a three fold increased risk of breast cancer [odds ratio (OR) = 3.21, 95% confidence interval (CI): 1.15–8.47].

Conclusion

The results suggest that obesity in postmenopausal women could increase risk of breast cancer and it merits further investigation in populations such as Iran where it seems that many women are short in height, and have a relatively high body mass index.