Early body size and subsequent weight gain as predictors of breast cancer incidence (Iowa, United States)

Maximum and Time-Dependent Body Mass Index and Breast Cancer Incidence Among Postmenopausal Women in the Black Women's Health Study

While excess weight is an established risk factor for postmenopausal breast cancer, consideration of maximum body mass index (maxBMI; BMI is calculated as weight (kg)/height (m)2) or BMI at a point in time relevant for breast carcinogenesis may offer new insights. We prospectively evaluated maxBMI and time-dependent BMI in relation to breast cancer incidence among 31,028 postmenopausal women in the Black Women's Health Study. During 1995-2015, a total of 1,384 diagnoses occurred, including 787 estrogen-receptor (ER)-positive (ER+) cases and 310 ER-negative (ER-) cases. BMI was assessed at baseline and 2, 4, 6, and 8 years before diagnosis. Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). Compared with women with BMI <25, those with BMI ≥35 had increased risk of ER+ breast cancer but not ER- breast cancer. For BMI assessed 2 years before diagnosis, the HRs for ER+ breast cancer associated with maxBMI ≥35 and time-dependent BMI ≥35 were 1.42 (95% confidence interval (CI): 1.10, 1.84) and 1.63 (95% CI: 1.25, 2.13), respectively. The corresponding HR for time-dependent BMI assessed 6 years before diagnosis was 1.95 (95% CI: 1.45, 2.62). These findings suggest strong associations of BMI with risk of ER+ breast cancer in postmenopausal women, regardless of timing of BMI assessment.

Risk of breast cancer in men in relation to weight change: a national case‐control study in England and Wales

Breast cancer is uncommon in men and knowledge about its causation limited. Obesity is a risk factor but there has been no investigation of whether weight change is an independent risk factor, as it is in women. In a national case‐control study, 1998 men with breast cancer incident in England and Wales during 2005 to 2017 and 1597 male controls were interviewed about risk factors for breast cancer including anthropometric factors at several ages. Relative risks of breast cancer in relation to changes in body mass index (BMI) and waist/height ratios at these ages were obtained by logistic regression modelling. There were significant trends of increasing breast cancer risk with increase in BMI from age 20 to 40 (odds ratio [OR] 1.11 [95% confidence interval (CI) 1.05‐1.17] per 2 kg/m² increase in BMI; P < .001), and from age 40 to 60 (OR 1.12 [1.04‐1.20]; P = .003), and with increase in self‐reported adiposity compared to peers at age 11 to BMI compared with peers at age 20 (OR 1.19 [1.09‐1.30]; P < .001). Increase in waist/height ratio from age 20 to 5 years before diagnosis was also highly significantly associated with risk (OR 1.13 [1.08‐1.19]; P < .001). The associations with increases in BMI and waist/height ratio were significant independently of each other and of BMI or waist/height ratio at the start of the period of change analysed, and effects were similar for invasive and in situ tumours separately. Increases in BMI and abdominal obesity are each risk factors for breast cancer in men, independently of obesity per se. These associations might relate to increasing oestrogen levels with weight gain, but this needs investigation.

What's new?

Although obesity is an established risk factor for breast cancer in men, there have been no investigations of whether weight change is an independent risk factor, as it is in women. In an interview case‐control study including 1998 cases and 1597 controls, authors found that increase in body mass index and in abdominal obesity are each significant risk factors for breast cancer in men, independent of obesity per se.

Adult weight change and the risk of pre- and postmenopausal breast cancer in the Chinese Wuxi Exposure and Breast Cancer Study

PURPOSE

The accumulating evidence indicates that weight gain in adulthood is more predictive of breast cancer risk than absolute body weight. However, the relative impact of timing of weight gain in adulthood on breast cancer as well as other characteristics of the association between weight and breast cancer has not been well documented.

METHODS

This population-based case-control study of breast cancer included 818 patients with newly diagnosed primary breast cancer and 935 residence and age-matched healthy controls. The body weight values at 18 years old, 1 year before diagnosis, and at menopause were obtained during in-person interviews. Unconditional logistic regression was used to estimate the effects of the weight change over adulthood on breast cancer risk. Linear mixed-effects regression was also applied as a secondary analysis.

RESULTS

We found that the increased risk of breast cancer was associated with the weight gain in adulthood among postmenopausal women (OR 1.23; 95% CI 1.10-1.37 per 5 kg increase) but not in the premenopausal women. The risk associated with weight gain since menopause (OR 1.65; 95% CI 1.28-2.14 a 5-kg increase) was higher than that from age 18 to menopause (OR 1.14; 95% CI 1.02, 1.28 a 5-kg increase). The association tended to be stronger in those with higher waist circumference and who had never used hormone replacement therapy (HRT). Women who had never used HRT, the increased risk of breast cancer associated with weight gain was more consistent in leaner women at age 18 (BMI < 18.5) or at menopause (BMI < 24).

CONCLUSIONS

Our findings indicated that weight gain has significant impact on postmenopausal breast cancer risk. The time periods of weight gain, central body fat, and HRT may affect the observed association, which should be further studied.

Energy-Related Indicators and Breast Cancer Risk among White and Black Women

Energy-related indicators, including physical activity, energy intake, body mass index (BMI) and adult weight change, have been linked to breast cancer risk. Very few studies of these associations have been conducted among black women, therefore we used the Nashville Breast Health Study (NBHS) to determine whether similar effects were seen in black and white women. The NBHS is a population-based case-control study of breast cancer among women age 25 to 75 years conducted between 2001 and 2010 in and around the Nashville Metropolitan area. Telephone interviews and self-administered food frequency questionnaires were completed with 2,614 incident breast cancer cases ascertained through hospitals and the statewide cancer registry, and 2,306 controls selected using random digit dialing. Among premenopausal white and black women, there was little effect of adult exercise or other energy-related indicators on breast cancer risk, regardless of tumor estrogen receptor (ER) status. The beneficial effect of adult exercise on postmenopausal breast cancer appeared to be comparable between white and black women (highest tertile relative to none - white odds ratio [OR] 0.8, 95% confidence interval [CI] 0.6-1.0, p for trend=0.05; black OR 0.7, 95% CI 0.4-1.1, p for trend=0.07); however, among black women the reduction was limited to those with ER-positive disease. White and black women should be encouraged to engage in more physical activity to reduce their risk of postmenopausal breast cancer.

Body size throughout adult life influences postmenopausal breast cancer risk among hispanic women: the breast cancer health disparities study

BACKGROUND

Few studies have assessed the association of body size with postmenopausal breast cancer risk in Hispanic women. Findings are inconsistent and appear to contradict those reported for non-Hispanic white (NHW) women.

METHODS

We pooled interview and anthropometric data for 2,023 Hispanic and 2,384 NHW women from two U.S. population-based case-control studies. Using logistic regression analysis, we examined associations of overall and abdominal adiposity with risk of postmenopausal breast cancer defined by estrogen receptor (ER) and progesterone receptor (PR) status.

RESULTS

Weight gain was associated with increased risk of ER(+)PR(+) breast cancer in Hispanics not currently using menopausal hormone therapy (HT), but only among those with a low young-adult body mass index (BMI). In the subset of Hispanics with data on genetic ancestry, the association with weight gain was limited to women with lower Indigenous American ancestry. Young-adult BMI was inversely associated with both ER(+)PR(+) and ER(-)PR(-) breast cancers for both ethnicities combined, with similar, although nonsignificant, inverse trends in Hispanics and NHWs. Among all Hispanics, regardless of HT use, height was associated with risk of ER(-)PR(-) breast cancer and hip circumference with risk of breast cancer overall.

CONCLUSIONS

Body size throughout adult life is associated with breast cancer risk among postmenopausal Hispanic women, as has been reported for NHW women. Associations were specific for breast cancer subtypes defined by hormone receptor status.

IMPACT

Avoiding weight gain and maintaining a healthy weight are important strategies to reduce the risk of postmenopausal ER(+)PR(+) breast cancer, the most common breast cancer subtype.

Body mass index at early adulthood, subsequent weight change and cancer incidence and mortality

Obesity later in adulthood is associated with increased risks of many cancers. However, the effect of body fatness in early adulthood, and change in weight from early to later adulthood on cancer risk later in life is less clear. We used data from 13,901 people aged 45-64 in the Atherosclerosis Risk in Communities cohort who at baseline (1987-1989) self-reported their weight at the age of 25 and had weight and height measured. Incident cancers were identified through 2006 and cancer deaths were ascertained through 2009. Multivariable Cox proportional hazard models were used to relate body mass index (BMI) at age 25 and percent weight change from age 25 to baseline to cancer incidence and mortality. After adjusting for weight change from age 25 until baseline, a 5 kg/m(2) increment in BMI at age 25 was associated with a greater risk of incidence of all cancers in women [hazard ratio (95% confidence interval): 1.10 (1.02-1.20)], but not in men. Associations with incident endometrial cancer were strong [1.83 (1.47-2.26)]. After adjusting for BMI at age 25, a 5% increment in weight from age 25 to baseline was associated with a greater risk of incident postmenopausal breast cancer [1.05 (1.02-1.07)] and endometrial cancer [1.09 (1.04-1.14)] in women and incident colorectal cancer [1.05 (1.00-1.10)] in men. Excess weight during young adulthood and weight gain from young to older adulthood may be independently associated with subsequent cancer risk. Excess weight and weight gain in early adulthood should be avoided.

Weight change in middle adulthood and breast cancer risk in the EPIC-PANACEA study

Long-term weight gain (i.e., weight gain since age 20) has been related to higher risk of postmenopausal breast cancer, but a lower risk of premenopausal breast cancer. The effect of weight change in middle adulthood is unclear. We investigated the association between weight change in middle adulthood (i.e., women aged 40-50 years) and the risk of breast cancer before and after the age of 50. We included female participants of the European Prospective Investigation into Cancer and Nutrition cohort, with information on anthropometric measures at recruitment and after a median follow-up of 4.3 years. Annual weight change was categorized using quintiles taking quintile 2 and 3 as the reference category (-0.44 to 0.36 kg/year). Multivariable Cox proportional hazards regression analysis was used to examine the association. 205,723 women were included and 4,663 incident breast cancer cases were diagnosed during a median follow-up of 7.5 years (from second weight assessment onward). High weight gain (Q5: 0.83-4.98 kg/year) was related to a slightly, but significantly higher breast cancer risk (HRQ5_versus_Q2/3 : 1.09, 95% CI: 1.01-1.18). The association was more pronounced for breast cancer diagnosed before or at age 50 (HRQ5_versus_Q2/3 : 1.37, 95% CI: 1.02-1.85). Weight loss was not associated with breast cancer risk. There was no evidence for heterogeneity by hormone receptor status. In conclusion, high weight gain in middle adulthood increases the risk of breast cancer. The association seems to be more pronounced for breast cancer diagnosed before or at age 50. Our results illustrate the importance of avoiding weight gain in middle adulthood.

Risk determination and prevention of breast cancer

Breast cancer is an increasing public health problem. Substantial advances have been made in the treatment of breast cancer, but the introduction of methods to predict women at elevated risk and prevent the disease has been less successful. Here, we summarize recent data on newer approaches to risk prediction, available approaches to prevention, how new approaches may be made, and the difficult problem of using what we already know to prevent breast cancer in populations. During 2012, the Breast Cancer Campaign facilitated a series of workshops, each covering a specialty area of breast cancer to identify gaps in our knowledge. The risk-and-prevention panel involved in this exercise was asked to expand and update its report and review recent relevant peer-reviewed literature. The enlarged position paper presented here highlights the key gaps in risk-and-prevention research that were identified, together with recommendations for action. The panel estimated from the relevant literature that potentially 50% of breast cancer could be prevented in the subgroup of women at high and moderate risk of breast cancer by using current chemoprevention (tamoxifen, raloxifene, exemestane, and anastrozole) and that, in all women, lifestyle measures, including weight control, exercise, and moderating alcohol intake, could reduce breast cancer risk by about 30%. Risk may be estimated by standard models potentially with the addition of, for example, mammographic density and appropriate single-nucleotide polymorphisms. This review expands on four areas: (a) the prediction of breast cancer risk, (b) the evidence for the effectiveness of preventive therapy and lifestyle approaches to prevention, (c) how understanding the biology of the breast may lead to new targets for prevention, and (d) a summary of published guidelines for preventive approaches and measures required for their implementation. We hope that efforts to fill these and other gaps will lead to considerable advances in our efforts to predict risk and prevent breast cancer over the next 10 years.

Association of skirt size and postmenopausal breast cancer risk in older women: a cohort study within the UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS)

OBJECTIVES

Several studies suggest that overall and central-obesity are associated with increased breast cancer (BC) risk in postmenopausal-women. However, there are no studies investigating changes of central obesity and BC. We report on the association of BC risk with self-reported skirt size (SS; waist-circumference proxy) changes between 20s and postmenopausal-age.

DESIGN

Prospective cohort-study.

SETTING

UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS) involving the nine trial centres in England.

PARTICIPANTS

Postmenopausal-women aged >50 with no known history of BC prior to or on the day of completion of the study-entry questionnaire.

INTERVENTIONS

At recruitment and at study entry, women were asked to complete a questionnaire. Women were followed-up via 'flagging' at the NHS Information Centre in England and the Hospital Episode Statistics.

MAIN OUTCOME-MEASURE

Time to initial BC diagnosis.

RESULTS

Between 2 January 2005 and 1 July 2010, 92,834 UKCTOCS participants (median age 64.0) completed the study-entry questionnaire. During median follow-up of 3.19 years (25th-75th centile: 2.46-3.78), 1090 women developed BC. Model adjusted analysis for potential confounders showed body mass index (BMI) at recruitment to UKCTOCS (HR for a 5 unit change=1.076, 95% CI 1.012 to 1.136), current SS at study entry (HR=1.051; 95% CI 1.014 to 1.089) and change in SS per 10 years (CSS) (HR=1.330; 95% CI 1.121 to 1.579) were associated with increased BC risk but not SS at 25 (HR=1.006; 95% CI 0.958 to 1.056). CSS was the most predictive singe adiposity measure and further analysis including both CSS and BMI in the model revealed CSS remained significant (HR=1.266; 95% CI 1.041 to 1.538) but not BMI (HR=1.037; 95% CI 0.970 to 1.109).

CONCLUSIONS

CSS is associated with BC risk independent of BMI. A unit increase in UK SS (eg, 12-14) every 10-years between 25 and postmenopausal-age is associated with postmenopausal BC risk by 33%. Validation of these results could provide women with a simple and easy to understand message.

TRIAL REGISTRATION NUMBER

ISRCTN22488978.

Body size, modifying factors, and postmenopausal breast cancer risk in a multiethnic population: the San Francisco Bay Area Breast Cancer Study

Data on body size and postmenopausal breast cancer in Hispanic and African American women are inconsistent, possibly due to the influence of modifying factors. We examined associations between adiposity and risk of breast cancer defined by hormone receptor status in a population-based case-control study conducted from 1995-2004 in the San Francisco Bay Area. Multivariate adjusted odds ratios and 95% confidence intervals were calculated using unconditional logistic regression. Associations with body size were limited to women not currently using menopausal hormone therapy (801 cases, 1336 controls). High young-adult body mass index (BMI) was inversely associated with postmenopausal breast cancer risk, regardless of hormone receptor status, whereas high current BMI and high adult weight gain were associated with two-fold increased risk of estrogen receptor and progesterone receptor positive breast cancer, but only in women with a low young-adult BMI (≤22.4 kg/m(2)) or those with ≥15 years since menopause. Odds ratios were stronger among non-Hispanic Whites than Hispanics and African Americans. Waist circumference and waist-to-height ratio increased breast cancer risk in Hispanics and African Americans only, independent of BMI. These findings emphasize the importance of considering tumor hormone receptor status and other modifying factors in studies of racially/ethnically diverse populations.

Female Body Mass Index and its Relationship With Triple Negative Breast Cancer and Ethnicity

BACKGROUND

Breast cancer in women is a relatively common malignancy in the western hemisphere and is perhaps one of the leading causes of mortality among females. We conducted a retrospect cohort study to investigate the association of body mass index (BMI) with triple negative breast cancer and ethnicity.

METHODS

Tumor Registry Database at the University of Florida, College of Medicine in Jacksonville was utilized for our cohort study. A total of 84 women with triple negative breast cancer, between 2004 and 2008 met our criteria and were selected for this study. For comparison, another 83 women with at least one hormone receptors positive breast cancer were randomly selected in the same time period. Chi-square testing was used to evaluate categorical variables, while the t-test analysis was used to analyze for the continuous variables.

RESULTS

Our data demonstrated that 27.4% of the triple negative group had BMI < 25 compared to the 14.5% of non-triple negative breast cancer, 73.6% of the triple negative group had BMI ≥ 25 compared to 86.5% in the non-triple negative group with a P-value of 0.245. In terms of ethnicity, triple negative breast cancer was found in 56% of African-American and 44% of Caucasian females. Non-triple negative breast cancer was found in 48.2% of African-Americans and 51.8% of Caucasians females with a P-value of 0.354.

CONCLUSIONS

We were not able to show any statistically significant association of body mass index triple with triple negative breast cancer or ethnicity. While our findings are not in agreement with the research published earlier, we do submit that our retrospective cohort study has shortcomings, including the small sample size pooled from a single center, which greatly limits our ability to deduce any definitive conclusions. In light of these shortcomings, we recommend a future multicenter study with a larger sample size.

Obesity/weight gain and breast cancer risk: findings from the Japan collaborative cohort study for the evaluation of cancer risk

BACKGROUND

We analyzed data from the Japan Collaborative Cohort Study (36 164 women aged 40-79 years at baseline in 1988-1990 with no previous diagnosis of breast cancer and available information on weight and height) to examine the association between baseline body mass index (BMI)/weight gain from age 20 years and breast cancer risk in a non-Western population.

METHODS

The participants were followed prospectively from enrollment until 1999-2003 (median follow-up: 12.3 years). During follow-up, breast cancer incidence was mainly confirmed through record linkage to population-based cancer registries. A Cox proportional hazards model was used to calculate hazard ratios (HRs) and 95% CIs for the association between breast cancer risk and body size.

RESULTS

In 397 644.1 person-years of follow-up, we identified 234 breast cancer cases. Among postmenopausal women, the adjusted HR increased with BMI, with a significant linear trend (P < 0.0001). Risk was significantly increased among women with a BMI of 24 or higher (HR: 1.50, 95% CI: 1.09-2.08 for BMI of 24-28.9, and 2.13, 1.09-4.16 for BMI ≥ 29) as compared with women with a BMI of 20 to 23.9. Weight gain after age 20 years and consequent overweight/obesity were combined risk factors for postmenopausal breast cancer risk. This combined effect was stronger among women aged 60 years or older. However, the HRs were not significant in premenopausal women.

CONCLUSIONS

Our findings support the hypothesis that weight gain and consequent overweight/obesity are combined risk factors for breast cancer among postmenopausal women, particularly those aged 60 years or older.

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

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

Adiposity, adult weight change and breast cancer risk in postmenopausal Japanese women: the Miyagi Cohort Study

Background:

The role of adult weight change in breast cancer (BC) risk is unclear in Japanese women.

Methods:

A total of 10 106 postmenopausal women aged 40–64 years (the Miyagi Cohort) were followed from 1990 to 2003, and 108 BC cases were identified. Hazard ratios (HRs) were estimated according to body mass index (BMI) at the current age and at the of age 20 years, and weight change since age 20 years.

Results:

Higher current BMI was associated with an increased risk of BC (P for trend=0.02), whereas higher BMI at the age 20 years was inversely associated with this risk (P for trend=0.002). There was a significant association between weight change since age 20 years and BC risk (P for trend=0.0086). Compared with stable weight, HR was 0.35 for weight loss of 5 kg or more (P for weight loss trend=0.04) and 1.55 for weight gain of 12 kg or more (P for weight gain trend=0.05).

Conclusion:

Adiposity at younger and current age has differential effects on BC risk among postmenopausal women; weight gain in adulthood being associated with an increased, and weight loss with a decreased risk.

The modifying effect of social class on the relationship between body mass index and breast cancer incidence

OBJECTIVES

We sought to determine whether social class modifies the effect of BMI on breast cancer incidence.

METHODS

Participants included 5642 postmenopausal White women recruited in 1989 to CLUE II, a prospective cohort study in Washington County, Maryland. We obtained exposure data from CLUE II and the 1990 US Census. We used survival and random-effects Cox proportional hazards analyses to determine the association of social class and BMI with breast cancer incidence.

RESULTS

Education was independently associated with increased risk of breast cancer incidence (hazard ratio [HR]=1.06; 95% confidence interval [CI]=1.01, 1.11; P<.05); contextual measures of social class were not. Education modified the effect of BMI at age 21 years (HR=0.98; 95% CI=0.97, 0.99); area-level social class modified the effect of BMI at baseline (HR=0.97; 95% CI=0.94, 0.99) and BMI change (HR=0.98; 95% CI=0.95, 1.00). Subpopulation analyses that were adjusted for hormone use, parity, and breast-feeding found similar effects.

CONCLUSIONS

Social class moderates the influence of body size on breast cancer incidence. Public health efforts, therefore, should advocate for policies that improve social conditions to decrease the burden of breast cancer.

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.

Prevention of breast cancer in postmenopausal women: approaches to estimating and reducing risk

BACKGROUND

It is uncertain whether evidence supports routinely estimating a postmenopausal woman's risk of breast cancer and intervening to reduce risk.

METHODS

We systematically reviewed prospective studies about models and sex hormone levels to assess breast cancer risk and used meta-analysis with random effects models to summarize the predictive accuracy of breast density. We also reviewed prospective studies of the effects of exercise, weight management, healthy diet, moderate alcohol consumption, and fruit and vegetable intake on breast cancer risk, and used random effects models for a meta-analyses of tamoxifen and raloxifene for primary prevention of breast cancer. All studies reviewed were published before June 2008, and all statistical tests were two-sided.

RESULTS

Risk models that are based on demographic characteristics and medical history had modest discriminatory accuracy for estimating breast cancer risk (c-statistics range = 0.58-0.63). Breast density was strongly associated with breast cancer (relative risk [RR] = 4.03, 95% confidence interval [CI] = 3.10 to 5.26, for Breast Imaging Reporting and Data System category IV vs category I; RR = 4.20, 95% CI = 3.61 to 4.89, for >75% vs <5% of dense area), and adding breast density to models improved discriminatory accuracy (c-statistics range = 0.63-0.66). Estradiol was also associated with breast cancer (RR range = 2.0-2.9, comparing the highest vs lowest quintile of estradiol, P < .01). Most studies found that exercise, weight reduction, low-fat diet, and reduced alcohol intake were associated with a decreased risk of breast cancer. Tamoxifen and raloxifene reduced the risk of estrogen receptor-positive invasive breast cancer and invasive breast cancer overall.

CONCLUSIONS

Evidence from this study supports screening for breast cancer risk in all postmenopausal women by use of risk factors and breast density and considering chemoprevention for those found to be at high risk. Several lifestyle changes with the potential to prevent breast cancer should be recommended regardless of risk.

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.

Measures of energy balance and mammographic density in the Nurses' Health Study

Mammographic density is a strong risk factor for breast cancer; however the mechanism that underlies this association is unclear. We hypothesized that measures of energy balance early in life and in adulthood may be associated with mammographic density. We conducted a cross-sectional analysis of 1,398 women in the Nurses' Health Study to examine associations between physical activity, childhood and current body fatness, weight gain from age 18 years to present and mammographic density. Percent mammographic density was measured from digitized mammograms by a computer-assisted method. Demographic and lifestyle data were obtained from prospectively collected questionnaires. For all analyses, subjects were stratified into three groups: premenopausal women, postmenopausal women not currently taking hormones, and postmenopausal women currently taking hormones. Childhood body fatness was inversely associated with mammographic density. The correlations ranged from -0.15 to -0.19 in the three strata of women (P<or=0.001). The difference in mean percent mammographic density between the leanest and heaviest body types ranged from 6.2 to 9.9%. Similarly, adult body fatness was inversely associated with percent mammographic density. The correlations ranged from -0.41 to -0.48 in the three strata of women (P<0.0001). The difference in mean percent mammographic density between the leanest and heaviest body types ranged from 22.3 to 35.1%. Weight gain from age 18 was also inversely associated with mammographic density. There was no association between recent physical activity and mammographic density. These findings indicate that childhood and adult body fatness and weight change from age 18 are inversely associated with mammographic density.

Lifetime adult weight gain, central adiposity, and the risk of pre- and postmenopausal breast cancer in the Western New York exposures and breast cancer study

While there are quite consistent data regarding associations of body weight and postmenopausal breast cancer, there are now accumulating data that would indicate that weight gain in adult life is more predictive of risk than absolute body weight. There is, however, little known about the relative impact of timing of weight gain in adult life as well as other characteristics of the weight and breast cancer association that might provide insight into the mechanism of the observation. We conducted a population-based case control study of breast cancer (1996-2001), the Western New York Exposures and Breast Cancer Study. Included were 1,166 women with primary, histologically confirmed, incident breast cancer and 2,105 controls frequency-matched on age, race and county of residence. Unconditional logistic regression was used to estimate odds ratios and 95% confidence intervals. We found increased risk of breast cancer associated with lifetime adult weight gain among post- but not premenopausal women, and there was a 4% increase in risk for each 5 kg increase in adult weight. Further there was a tendency toward a stronger association for those with higher waist circumference and those with positive estrogen or progesterone status, and who had never used HRT. We also found an association with risk for weight gain since first pregnancy and for weight gain between the time of the first pregnancy and menopause, independent of body mass index and lifetime adult weight gain. Our results suggest that there are time periods of weight gain that have greater impact on risk, and that central body fat, receptor status and hormone replacement therapy may all affect the observed association.

Polymorphisms in O 6-methylguanine DNA methyltransferase and breast cancer risk

OBJECTIVE

Endogenous and exogenous estrogens influence breast cancer risk by interacting with estrogen receptor (ER). The O-methylguanine DNA methyltransferase (MGMT) gene has a dual role in repairing alkylation damage and in inhibiting ER-mediated cell proliferation. We assessed the two MGMT polymorphisms, Leu84Phe and Ile143Val, with breast cancer risk. We also evaluated the potential interactions between the two polymorphisms and estrogen-related risk factors and cigarette smoking on breast cancer risk.

METHODS

We conducted a nested case-control study within the Nurses' Health Study (1311 cases, 1760 controls).

RESULTS

Compared with the 84Leu/Leu genotype, the Phe/Phe genotype had a multivariate odds ratio (OR) of 1.68 (95% confidence interval (CI), 0.98-2.88). This positive association was magnified among postmenopausal women with body mass index>25 (OR, 3.01; 95% CI, 1.30-6.94), those in the highest tertile of pre-diagnostic plasma endogenous estradiol levels (Phe carriers versus non-carriers, OR, 2.42; 95% CI, 1.49-3.94), non-current postmenopausal hormone users (OR, 2.60; 95% CI, 1.19-5.64), and possibly estrogen receptor-positive cases (OR, 1.82; 95% CI, 0.99-3.35). We did not observe a main effect of the Ile143Val polymorphism or its interactions with these factors. No interaction was observed between either of the polymorphisms and cigarette smoking on breast cancer risk.

CONCLUSIONS

These data suggest that the Leu84Phe polymorphism affect the capacity of MGMT to inhibit estrogen receptor-mediated cell proliferation and is associated with breast cancer risk.

Measures of adiposity and risk of breast cancer in older postmenopausal women

OBJECTIVES

To determine whether higher adiposity is associated with greater breast cancer risk in older postmenopausal women.

DESIGN

Prospective cohort study with mean follow-up of 11.3 years.

SETTING

Four U.S. clinical centers.

PARTICIPANTS

Seven thousand five hundred twenty-three women (mean age 73.5) enrolled in the Study of Osteoporotic Fractures.

MEASUREMENTS

Weight, height, and waist and hip circumference were measured at baseline. Body composition was determined using bioelectrical impedance. Risk factor information was obtained by interview and questionnaire. Bone mineral density was measured using dual energy x-ray absorptiometry. The outcome was incident invasive breast cancer, confirmed using medical records.

RESULTS

After adjustment for multiple risk factors, including bone density, women in the uppermost quartiles of weight, weight gain since age 25, body mass index, waist circumference, and percentage of body fat had higher breast cancer rates than women in the first quartiles of each measure. For example, breast cancer rates were 49% higher for women in the uppermost quartile of weight (hazard ratio (HR)=1.49, 95% confidence interval (CI)=1.05-2.10), 64% higher for women in the top quartile of weight gain since age 25 (HR=1.64, 95% CI=1.15-2.34), and 58% higher for women in the top quartile of percentage of body fat (HR=1.58, 95% CI=1.11-2.23) than for women in the lowest quartile of each measure. The associations between adiposity measures and breast cancer rates were not altered when the analyses were limited to very elderly women (> or = 70).

CONCLUSION

Higher adiposity is an independent risk factor for breast cancer in elderly women.

Role of Lipid Peroxidation in the Epidemiology and Prevention of Breast Cancer

We have recently proposed a common mechanistic pathway by which obesity and hypertension lead to increased renal cell cancer risk. Our hypothesis posits lipid peroxidation, which is a principal mechanism in rodent renal carcinogenesis, as an intermediate step that leads to a final common pathway shared by numerous observed risks (including obesity, hypertension, smoking, oophorectomy/hysterectomy, parity, preeclampsia, diabetes, and analgesics) or protective factors (including oral contraceptive use and alcohol) for renal cell cancer [Cancer Causes Control 2002;13:287-93]. During this exercise, we have noticed how certain risk factors for renal cell carcinoma are protective for breast cancer and how certain protective factors for renal cell carcinoma increase risk for breast cancer. Parity and oophorectomy, for example, are positively associated with renal cell carcinoma but are negatively associated with breast cancer. Similarly, obesity and hypertension are positively associated with renal cell carcinoma, but obesity is negatively associated with breast cancer in premenopausal women and hypertension during pregnancy is negatively associated with breast cancer. Furthermore, alcohol intake, negatively associated with renal cell carcinoma, is also positively associated with breast cancer. We propose here the possibility that lipid peroxidation may represent a protective mechanism in breast cancer. Although this runs counter to the conventional view that lipid peroxidation is a process that is harmful and carcinogenic, we present here the chemical and biological rationale, based on epidemiologic and biochemical data, which may deserve further consideration and investigation.

Body mass and mortality after breast cancer diagnosis

Obesity is an established risk factor for some breast cancers, but less is known about its effect on breast cancer prognosis. Understanding this relationship is important, given the increasing number of women diagnosed with breast cancer and the growing prevalence of obesity. We conducted a cohort analysis of 3,924 women ages 20 to 54 with incident breast cancer enrolled between 1980 and 1982 in the Cancer and Steroid Hormone study, a case-control study. Interview data were linked to survival information from the Surveillance, Epidemiology, and End Results Program. We used proportional hazards models to examine the relationship between breast cancer mortality and adult body mass index (BMI; calculated using usual adult weight), BMI at age 18, and weight change from age 18 to adulthood. Hazard ratios (HR) were adjusted for cancer stage and other factors. During a median follow-up of 14.6 years, 1,347 women died of breast cancer. Obese women (adult BMI>or=30.00) were significantly more likely than lean women (BMI<or=22.99) to die of breast cancer [HR, 1.34; 95% confidence interval (CI), 1.09-1.65]. Women with BMIs of 25.00-29.99 (HR, 1.25; 95% CI, 1.08-1.44) or 23.00-24.99 (HR, 1.20; 95% CI, 1.04-1.39) also had higher breast cancer mortality (P for trend <0.0001). BMI at age 18 and weight change were not associated with breast cancer mortality independently of other factors. Obesity could be a preventable risk factor for death among breast cancer patients. Further study is needed to determine how these findings might affect recommendations to reduce breast cancer mortality.

Long-term weight change and breast cancer risk: the European prospective investigation into cancer and nutrition (EPIC)

We examined prospectively the association between weight change during adulthood and breast cancer risk, using data on 1358 incident cases that developed during 5.8 years of follow-up among 40 429 premenopausal and 57 923 postmenopausal women from six European countries, taking part in the European prospective investigation into cancer and nutrition study. Multivariate Cox regression models were used to calculate hazard ratios according to weight change (kg), defined as the weight difference between age at enrolment and age 20 adjusted for other risk factors. Changes in weight were not associated with premenopausal breast cancer risk. In postmenopausal women, weight gain was positively associated with breast cancer risk only among noncurrent hormone replacement therapy (HRT) users (P-trend ⩽0.0002). Compared to women with a stable weight (±2 kg), the relative risk for women who gained 15–20 kg was 1.50 (95% confidence interval (CI) 1.06–2.13). The pooled RR per weight gain increment of 5 kg was 1.08 (95% CI 1.04–1.12). Weight gain was not associated with breast cancer risk in current HRT users, although, overall, these women experienced a much higher risk of breast cancer compared with nonusers. Our findings suggest that large adult weight gain was a significant predictor of breast cancer in postmenopausal women not taking exogenous hormones.

Body size changes in relation to postmenopausal breast cancer among women on Long Island, New York

To examine effects of body size change on postmenopausal breast cancer, the authors conducted a population-based case-control study among 990 cases and 1,006 controls participating in the Long Island Breast Cancer Study Project in 1996-1997. Women who had gained more than 15 kg (33 pounds) since age 20 years were at a 1.6-fold increased risk of breast cancer (95% confidence interval (CI): 1.11, 2.26) relative to their counterparts with stable (+/-3 kg) weight. Subjects who had gained more than 11 kg (24 pounds) during the peri- and postmenopausal years (since age 50 years) had 1.62 times the risk of breast cancer of those whose weight remained unchanged during this time period. This effect of peri- and postmenopausal body size gain was present only among never users of hormone replacement therapy (odds ratio (OR) = 2.02 (95% CI: 1.35, 3.02) as opposed to 0.81 (95% CI: 0.43, 1.53) for ever users; multiplicative interaction: p < 0.01) and was more pronounced among women with estrogen receptor-positive/progesterone receptor-positive breast cancer (OR = 2.17, 95% CI: 1.38, 3.42). Weight loss over the lifetime was associated with decreased risk of postmenopausal breast cancer (OR = 0.55, 95% CI: 0.32, 0.96). These results add to the literature by focusing on the perimenopausal weight trajectory and support efforts urging women to avoid weight gain as they age.

Association of gain and loss of weight before and after menopause with risk of postmenopausal breast cancer in the Iowa women's health study

Obesity and adult weight gain are well-established risk factors for postmenopausal breast cancer. Although there are a few studies demonstrating the contribution of adult weight gain to breast cancer risk, whether weight gain during a critical time period is specifically associated with risk, or whether subsequent weight loss among women who have gained weight will reduce the excess risk, is not firmly established. We investigated the association of changes in weight (loss or gain in excess of 5% of body weight) using two risk factor models: (a) age 18 to 30 years and age 30 years to menopause and (b) age 30 years to menopause and after the menopause to the baseline study in 1986 on risk of postmenopausal breast cancer in a prospective cohort of 33,660 postmenopausal women in Iowa. Over 15 years of follow-up, 1,987 cases of breast cancer occurred. Data were analyzed using proportional hazards regression models adjusted for established breast cancer risk factors. The most frequently observed pattern of body weight over time was a consistent increase; these women were observed to have the highest rates of breast cancer and served as the reference category for all comparisons. The lowest-risk groups were (a) women who maintained or lost weight from age 18 to 30 years and then lost weight from age 30 years to menopause [risk ratio (RR), 0.36; 95% confidence interval (95% CI), 0.22-0.60] and (b) women who maintained or lost weight from age 30 years to menopause and then lost weight after the menopause (RR, 0.48; 95% CI, 0.22-0.65). Women who gained weight from age 30 years to menopause but then lost weight after the menopause experienced risk reductions (RR, 0.77; 95% CI, 0.64-0.92) although perhaps slightly smaller in magnitude than women who maintained their weight in both time intervals (RR, 0.63; 95% CI, 0.55-0.73). Women who gained weight from age 18 to 30 years and then lost weight from age 30 years to menopause had comparable risk reductions (RR, 0.61; 95% CI, 0.46-0.8) with women who maintained their weight in both time intervals (RR, 0.73; 95% CI, 0.64-0.84). Women who gained weight during the period from age 30 years to menopause but who had stable weight after menopause had rates similar to the reference group. These data suggest prevention of weight gain between age 18 years and menopause or weight loss and maintenance during these years reduces risk of postmenopausal breast cancer.

Body mass index and breast cancer risk in African American women

PURPOSE

Studies of the relationship between body mass index (BMI) and breast cancer in African American women have been few. We conducted a case-control study to examine whether BMI is associated with risk of breast cancer in this population.

METHODS

Cases were 304 women diagnosed with breast cancer at the ages of 20 to 64 years. Controls were 305 women without a history of breast cancer. Telephone interviews were conducted to collect data on history of exposure to various factors at or before the date of diagnosis in cases or equivalent date in controls (reference date). Using logistic regression, we compared cases and controls in BMI at age 18, BMI at the reference date, and change in BMI between the two dates.

RESULTS

Using BMI at reference date, we found an odds ratio (OR) of 1.75 (95% confidence interval [CI], 1.02-3.02) and 2.32 (95% CI, 1.33-4.03) for women with BMI of 25 to 29.9 and 30 or higher, respectively, compared with women having BMI lower than 25. The corresponding OR estimates for BMI at age 18 were not significantly different from the unity. The average annual change in BMI between age 18 and date of diagnosis or reference date was associated with breast cancer risk, as shown that more BMI change tended to increase breast cancer risk compared with the baseline quartile of change. When data were analyzed by menopausal status, the association was found for both post-menopausal and pre-menopausal tumors for BMI at reference date but not for BMI at age 18. There was a higher risk for more annual BMI change compared with the baseline for both pre-menopausal and post-menopausal women.

CONCLUSION

Our results suggest that BMI at reference date and change in BMI were associated with increased risk of breast cancer in African American women, and the association might be found for both post-menopausal and pre-menopausal tumors.

A combined breast health/weight loss intervention for Black women

BACKGROUND

Overall incidence of breast cancer is slightly lower, but mortality rates are higher, for Black women compared to White women. Higher body mass index (BMI), sedentary lifestyles, and lower compliance with recommended breast health behaviors may contribute to higher risk and mortality.

METHODS

A randomized pilot intervention trial was conducted to assess feasibility and efficacy of a combined breast health/weight loss intervention for 64 overweight or obese Black women, ages 35-65. The primary objectives were to determine whether a 20-week (twice weekly) intervention could decrease weight and dietary fat intake and increase physical activity and breast self-exam (BSE) proficiency.

RESULTS

The project was implemented in two cohorts and retention was high for both (96% and 89%, respectively). Both cohorts showed increased proficiency in BSE in the intervention versus the control group (2.4 vs. -0.4, P<0.05; 3.3 vs. -0.2, P<0.001, respectively), but only cohort 2 showed decreased percent body weight (4.0% decrease vs. 0.9% increase, P<0.01), increased physical activity frequency (2.4 vs. 0.1 times/week, P<0.05), and a trend for decreased dietary fat (-2.6% kcal vs. 0.0% kcal, P=0.07) in the intervention compared to the control group.

CONCLUSION

Few studies have documented weight loss among Black women, and no combined breast health/weight loss intervention has been conducted. This study documents the feasibility of recruiting, randomizing, and retaining women in a combined intervention and demonstrated weight loss and associated lifestyle changes.

Strategies for managing breast cancer risk after the menopause

Postmenopausal women in Western societies are conscious of breast cancer as a potential cause of death and ill health, which they wish to avoid with the advice of their doctors. Yet many factors that predispose women to the development of cancer will have been laid down before the menopause, in their genetic makeup or during their adolescent years. Even in middle age it is important to take account of the intrinsic level of risk, and to give women advice tailored to their own individual risk level. This results from their family history, previous diseases such as benign breast disease, and previous treatment for breast cancer or Hodgkin's disease. For those at the highest level of risk, strategies will include regular screening, prophylactic mastectomy, and the use of chemoprevention agents, such as tamoxifen. These women should avoid hormone replacement therapy (HRT) and control their menopausal symptoms and osteoporosis through the use of other agents now available - venlafaxine for menopausal symptoms and bisphosphonates for osteoporosis. Raloxifene is an agent under trial that may be valuable for breast cancer control as well as for osteoporosis. Women at standard population risk will require less robust preventive strategies, which will include screening and lifestyle modification. Their decisions regarding HRT should now be modified by recent evidence of associated risks. Recent studies show that tibolone causes less mammographic density and has a lower relative risk of breast cancer than combined estrogen/progestogen preparations. There is limited evidence that controlling obesity, participating in exercise and adopting a diet low in fats and high in fruit and vegetables will alter risk at this age. These precautions will, however, reduce the risk of other diseases common in this age group, such as hypertension, heart disease, stroke, and type 2 diabetes mellitus. Alcohol, even in small amounts, is a risk factor for breast cancer. Given the cardioprotective effect of moderate alcohol intake, advice on alcohol must reflect the individual relative risk of cardiovascular disease and breast cancer. Personal risk assessment is relevant for all women. Screening and a healthy lifestyle are worthwhile approaches for all, with the more aggressive approaches such as chemoprevention and prophylactic surgery reserved for those who have substantially elevated levels of risk. Once the menopause has passed, screening is probably the most effective evidence-based tool for breast cancer control by early diagnosis.

Obesity and cancer

Large prospective studies show a significant association with obesity for several cancers, and the International Agency for Research on Cancer has classified the evidence of a causal link as 'sufficient' for cancers of the colon, female breast (postmenopausal), endometrium, kidney (renal cell), and esophagus (adenocarcinoma). These data, and the rising worldwide trend in obesity, suggest that overeating may be the largest avoidable cause of cancer in nonsmokers. Few obese people are successful in long-term weight reduction, and thus there is little direct evidence regarding the impact of weight reduction on cancer risk. If the correlation between obesity and cancer mortality is entirely causal, we estimate that overweight and obesity now account for one in seven of cancer deaths in men and one in five in women in the US.

Does diet affect breast cancer risk?

The role of specific dietary factors in breast cancer causation is not completely resolved. Results from prospective studies do not support the concept that fat intake in middle life has a major relation to breast cancer risk. However, weight gain in middle life contributes substantially to breast cancer risk. Alcohol is the best established dietary risk factor, probably by increasing endogenous estrogen levels. Hypotheses relating diet during youth to risk decades later will be difficult to test. Nevertheless, available evidence is strong that breast cancer risk can be reduced by avoiding weight gain during adult years, and by limiting alcohol consumption.

Weight Change and the Risk of Late-Onset Breast Cancer in the Original Framingham Cohort

OBJECTIVE

Adult weight gain has been associated with a twofold risk of postmenopausal breast cancer. Data are limited regarding whether weight gain at specific periods of marked changes in estrogen- and insulin-related hormones have different risk associations. This study assesses the relation of adult weight change overall and at specific, hormonally relevant times with diagnosis of a first breast cancer after age 55 (late onset).

METHODS

Framingham study data were used to assess premenopausal (25-44 yr), perimenopausal (45-55 yr), postmenopausal (after 55 yr), and adult lifetime (from 25 yr) weight change in relation to late-onset breast cancer in 2,873 women followed for up to 48 yr, with 206 late-onset breast cancers.

RESULTS

Adult lifetime weight gain was associated with an increased risk of late-onset breast cancer (P trend = 0.046). Weight gain during specific time periods was not associated with breast cancer. Data suggested a possible decreased risk of breast cancer with weight loss from ages 25 to 44 and 45 to 55 yr (relative risk = 0.4 [0.2-1.2] and 0.5 [0.3-0.9], respectively).

CONCLUSION

These data confirm prior reports of an association between adult lifetime weight gain and increased risk of late-onset breast cancer and support current recommendations to avoid adult weight gain.

Weight gain, body mass index, hormone replacement therapy, and postmenopausal breast cancer in a large prospective study

Excess adiposity and hormone replacement therapy (HRT) are important contributors to postmenopausal breast cancer risk. HRT has been shown to modify the association between body weight and breast cancer risk, although few studies are sufficiently large to examine the risk of breast cancer associated with body mass index (BMI) and weight gain separately among current HRT users and nonusers. This study includes 1,934 incident breast cancer cases occurring among 62,756 postmenopausal women in the Cancer Prevention Study-II Nutrition Cohort. Age-adjusted incidence rates were calculated, and Cox proportional hazards models were used to examine the association of BMI and adult weight gain (since age 18 years) with breast cancer risk stratified by HRT use. Total adult weight gain strongly predicted breast cancer risk among former and never HRT users (P for trend < 0.0001). Weight gain of 21-30 pounds was associated with a rate ratio of 1.4 (95% confidence interval 1.1-1.8); rates doubled among women gaining >70 pounds compared with women who maintained their weight within 5 pounds of their weight at age 18. After accounting for weight gain, neither recent BMI nor BMI at age 18 were independent predictors of risk. Among current HRT users, no association was seen between breast cancer and either BMI or weight gain. Adult weight gain is strongly associated with postmenopausal breast cancer only among non-HRT users in this study. These data illustrate the importance of examining breast cancer risk factors separately by HRT use; the effects of other risk factors may be attenuated or obscured among women taking HRT.

A meta-analysis of published literature on waist-to-hip ratio and risk of breast cancer

Epidemiological studies have identified body weight as a risk factor for breast cancer. Beyond the amount of adipose tissue a woman has, its distribution, particularly abdominally, may be a risk factor in breast cancer etiology. Body fat distribution is commonly measured by a waist-to-hip circumference ratio lpar;WHR). We performed a meta-analysis to summarize the published literature on WHR and breast cancer risk. After assembling all published studies, we extracted mean WHRs for study participants and adjusted risk estimates comparing highest with lowest partition of WHR and calculated weighted mean differences in WHR between cases and noncases and summary risk estimates based on study design and menopausal status. The weighted mean difference was 0.016 [95% confidence interval (CI) = 0.005-0.028] for all studies combined. The summary risk estimates were 1.80 (95% CI = 1.29-2.50) for case-control studies and 1.27 (95% CI = 1.07-1.51) for cohort studies. By menopausal status, the summary risks were 1.79 (95% CI = 1.22-2.62) for premenopausal women and 1.50 (95% CI = 1.10-2.04) for postmenopausal women. For all studies combined, the summary risk was 1.62 (95% CI = 1.28-2.04). This meta-analysis indicates that a greater WHR is associated with increased risk of breast cancer and suggests that the avoidance of abdominal obesity may reduce risk of the disease.

Central obesity and breast cancer risk: a systematic review

The specific effect of central rather than general obesity on breast cancer risk is not clear. This review examines the relationship between waist and waist-hip ratio (WHR) and risk of breast cancer in pre- and post-menopausal women using all available cohort and case-control data. The databases of the Cochrane Library, Medline, Cancer Lit and Embase were searched until October 2002. Relevant cohort and case-control studies with separate analyses in pre- and/or post-menopausal women were included. Random effects meta-analyses were carried out, subgrouped by pre- or post-menopausal status and cohort or case-control design. Sensitivity analyses were also performed. Five cohort studies with 72,1705 person years of observation (453 pre-menopausal and 2684 post-menopausal cases), and three case-control studies comprising 276 pre-menopausal cases with 758 pre-menopausal controls and 390 post-menopausal cases with 1071 post-menopausal controls were included. Pooled results from cohort studies using the most adjusted data [but without adjustment for weight or body mass index (BMI)] suggest a 39% lower risk of breast cancer in post-menopausal women with the smallest waist (compared with the largest) and a 24% lower risk in women with the smallest WHR. In pre-menopausal women, however, pooled results suggest that measurement of waist or WHR have little effect on risk of breast cancer. Adjustment for BMI abolished the relationship between waist or WHR and risk of post-menopausal breast cancer, but introduced such a relationship amongst pre-menopausal women. The relationship between a smaller measurement of waist or WHR and lower risk of post-menopausal breast cancer appears to result from the associated correlation with BMI. Amongst pre-menopausal women, central (not general) obesity may be specifically associated with an increased risk of breast cancer.

Breast cancer: occurrence, risk factors and hormone metabolism

Breast cancer is by far the most frequent cancer among women worldwide. Its determinants include reproductive events, exogenous and endogenous hormone levels and metabolism, exposures, such as radiation and chemicals, and genetics. This paper will review available evidence from all of these areas, exploring the occurrence of cancer, risk factors for occurrence and the hormonal milieu that underlies it.

Exposures in childhood, adolescence and early adulthood and breast cancer risk: a systematic review of the literature

A growing body of work indicates that exposures over the life course have important roles to play in the aetiology of breast cancer. This review synthesises the literature that has been published in the area of early life events and female breast cancer risk. The review finds some evidence, primarily from cohort studies on the relationship between birthweight and breast cancer, to suggest that in utero events are related to breast cancer risk in adulthood. Strong evidence to support a positive association between height and breast cancer exists. Postulated mechanisms for this relationship include the role of early diet in subsequent disease risk, and the influence of endogenous growth factors mediating the relationship. There is some evidence to suggest that leg length is the component of height which is generating the observed associations between height and breast cancer. There is no consistent pattern of association between relative weight in childhood or adolescence and risk of breast cancer. The evidence to suggest an association between physical activity in early life and breast cancer risk is convincing from case-control studies, but is not fully substantiated by the results of three cohort studies. There are inconsistent results regarding the association between smoking at a young age and breast cancer risk. There is little evidence for an association between passive smoking in early life and breast cancer risk. No clear association between early drinking and breast cancer risk exists. These results are discussed in relation to possible underlying mechanisms and health promotion strategies which could reduce breast cancer risk.

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

High BMI is a well-known risk factor for postmenopausal breast cancer. There have been some reports of excess risk in association with weight gain and WHR, but little is known about the influence of body fatness per se. Using data from the Malmö Diet and Cancer Study, a prospective cohort study, 12,159 postmenopausal women (59.9 +/- 7.7 years) were categorized by quintiles of baseline anthropometric and impedance measures and reported weight change since age 20. RRs from multivariate Cox regression models were calculated. All analyses were adjusted for age, height, smoking, alcohol consumption, occupation, marital status, parity, age at first pregnancy, age at menarche and current hormone use. During the 5.7 years of follow-up, there were 246 incident breast cancer cases. Weight, height, BMI and %BF were positively associated with risk of breast cancer (p(trend) <or= 0.02). %BF showed the strongest association, with an RR of 2.01 (95% CI 1.26-3.21) in the highest vs. lowest quintile. There was significant modification of this association by hormone use, suggesting a greater impact of body fatness among nonusers. Fat distribution was not independently associated with breast cancer risk. Women with weight gain >21 kg (top quintile) had an RR of 1.75 (95% CI 1.11-2.77) compared to women with low weight gain. Breast cancer risk in postmenopausal women is predicted by increased body fat and weight gain. %BF is a more discriminating risk factor for breast cancer incidence than the commonly used BMI.

Body mass index in young adulthood and cancer mortality: a retrospective cohort study

STUDY OBJECTIVE

To examine the relation between body mass index (BMI) in young adulthood and subsequent mortality from cancer.

DESIGN

Cohort study.

SETTING

University of Glasgow student health service. Weight and height were measured by a physician, and used to calculate BMI.

PARTICIPANTS

8335 men and 2340 women who attended the student health service while at university between 1948 and 1968, and who were followed up with the NHS central register.

MAIN RESULTS

The main outcome measure was cancer mortality. Three hundred and thirty nine men and 82 women died of cancer during the follow up (mean 41 years). BMI was associated with mortality from all cancers in men and women, although it did not reach conventional statistical significance. The adjusted hazard ratio (HR) (95% CI) per 5 kg/m(2), was 1.22 (0.97 to 1.53) in men and 1.43 (0.95 to 2.16) in women. Two hundred men and 61 women died from cancers not related to smoking. The adjusted HR for mortality from these were 1.36 (1.02 to 1.82) and 1.80 (1.13 to 2.86) respectively. These results are adjusted for height, number of siblings, pulse rate, year of birth, age, smoking, birth order, number of siblings, and age at menarche in women. Site specific analyses, comparing the highest with the lowest quartile of the BMI distribution found increased risks of prostate cancer (n=28) and breast cancer among heavier subjects. No association between BMI and colorectal cancer was found.

CONCLUSIONS

BMI in adolescence has lasting implications for risk of cancer mortality in later life. Future research will include measures of BMI throughout the lifecourse, to determine the period of greatest risk of obesity, in terms of cancer mortality.

Physical consequences of schizophrenia and its treatment: the metabolic syndrome

Schizophrenia is a life shortening illness. Unnatural causes and natural causes are put forward as reasons for this excess mortality. In terms of the latter, a host of different physical disorders occur with increased frequency in schizophrenia. When taken together, some of these illnesses such as type 2 diabetes mellitus and cardiovascular disorders constitute the Metabolic Syndrome; a characteristic phenotype of those with this syndrome is excessive visceral fat distribution. The exact reasons why this particular syndrome occurs in schizophrenia is as yet unclear though factors such as life style, poor diet and lack of exercise may contribute to it's development. Alternatively, overactivity of the hypothalamic-pituitary-adrenal axis leading to hypercortisolaemia can also result in excessive visceral fat accumulation. This minireview aims to explore the potential role of these issues and medication in terms of the increased morbidity and mortality observed in schizophrenia.

Association of body size and fat distribution with risk of breast cancer among Chinese women

Most previous studies addressing the association of body size, weight change and body fat distribution with the risk of breast cancer were conducted in Western societies with a high proportion of overweight people. It remains unclear whether the dose-response relation observed in earlier studies can be extended to women with "normal" weight based on prevailing Western standards. To address this issue, we analyzed data from a population-based case-control study of breast cancer recently completed among Chinese women in urban Shanghai. In-person interviews and anthropometric measurements were completed for 1,459 women newly diagnosed with breast cancer from 25 to 64 years of age and 1,556 controls frequency-matched to cases on age. Unconditional logistic regression was employed to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CI) related to anthropometric variables and self-reported body weight. Currently measured weight, body mass index [BMI: weight (kg)/height(m)(2)] or height was each found to be positively related to risk of postmenopausal breast cancer in a dose-response manner, with ORs (95% CI) being 2.0 (1.4-3.0), 2.0 (1.2-3.2) or 1.7 (1.2-2.5), respectively, for the highest category of weight, BMI or height compared to the lowest category of these variables. These variables were unrelated to premenopausal breast cancer risk. Reported weight at ages >40 years and weight gain after age 20 were more predictive for postmenopausal breast cancer than weight at an earlier age. After adjustment for BMI, waist-to-hip ratio was related to an increased risk of premenopausal [OR = 1.7 (1.3-2.3) for the highest category compared to the lowest category] but not postmenopausal breast cancer. This study suggests that, even in a relatively thin Chinese population, weight gain and height are related to an increased risk of postmenopausal breast cancer, while central fat distribution was associated with premenopausal breast cancer. General weight control may be an effective measurement for breast cancer prevention.

Relation of body mass index to tumor markers and survival among young women with invasive ductal breast carcinoma

BACKGROUND

Obesity has been shown to affect breast carcinoma prognosis, with the heaviest women having a higher mortality due to breast carcinoma. Few studies have focused on premenopausal women or the correlation of body mass index (BMI) to tumor characteristics related to prognosis.

METHODS

The authors conducted a population-based follow-up study for mortality of 1177 women younger than 45 years of age who had invasive ductal breast carcinoma diagnosed from 1983 through 1992. Histologic slides and/or tumor tissue were collected for pathologic review, immunohistochemistry assays, and bivariate flow cytometric analysis.

RESULTS

Women with breast carcinoma who were in the highest quartile of BMI were 2.5 times as likely (95% confidence interval [CI], 1.6-3.9) to die of their disease within 5 years of diagnosis compared with women in the lowest quartile of BMI. The tumors of the women in the highest quartile of BMI were more likely to be estrogen receptor negative (odds ratio [OR], 1.5; 95% CI, 1.0-2.2) and to have a high S-phase fraction (OR, 1.9; 95% CI, 1.2-3.1), high histologic grade (OR, 1.7; 95% CI, 1.0-2.9), high mitotic cell count (OR, 2.0; 95% CI, 1.2-3.1), and large tumor size (2 to < 5 cm: OR, 2.3; 95% CI, 1.5-3.1; or > or = 5 cm: OR, 2.7; 95% CI, 1.5-4.8) compared with the tumors of women whose BMI was in the first quartile. Relative to the large tumors (> or = 2 cm) in women in the lowest BMI quartile, the large tumors in women in the highest BMI quartile were more likely to express markers of high proliferation, indicating they may have grown faster than similar size tumors of the thinnest women. In a multivariate analysis including the tumor characteristics, obesity, as measured by being in the highest quartile of BMI, remained an independent prognostic factor for mortality (hazard ratio, 1.7; 95% CI, 1.0-2.9; P < 0.05.

CONCLUSIONS

Our study results indicated that being in the highest quartile of BMI was a strong predictor of mortality in women with breast carcinoma diagnosed at a young age. The tumors of the heavy women were larger and more likely to have markers of high cellular proliferation than those of thinner women.

Review of anthropometric factors and breast cancer risk

Epidemiological evidence implicating anthropometric risk factors in breast cancer aetiology is accumulating. For premenopausal women, breast cancer risk increases with increasing height, but decreases with higher weight or body mass index, and no association with increased central adiposity exists. For postmenopausal women, an increased risk of breast cancer is found with increasing levels of all the anthropometric variables including height, weight, body mass index, waist-hip ratio, waist circumference and weight gain. Weight loss appears to decrease risk, particularly if it occurs later in life. Breast size may be a risk factor for breast cancer, however, the current evidence is inconclusive. Several hypothesized biologic mechanisms exist to explain how anthropometric factors influence breast cancer risk. Obesity may increase levels of circulating endogenous sex hormones, insulin and insulin-like growth factors that all, in turn, increase breast cancer risk. Genetic predisposition to obesity and to specific body fat distributions are also implicated. With obesity, there are increased levels of fat tissue that can store toxins and can serve as a continuous source of carcinogens. Recommendations for future research on anthropometric factors and breast cancer are provided. Sufficient evidence exists to support strategies to avoid weight gain throughout life as a means of reducing postmenopausal breast cancer risk.