A study of diet and breast cancer

Total Energy Intake: Implications for Epidemiologic Analyses

In 1986, Willett and Stampfer (Am J Epidemiol. 1986;124(1):17-27) propelled the nutritional epidemiology field forward by publishing a commentary emphasizing the importance of analyzing diet in relation to total energy intake in epidemiologic analyses of diet and disease, detailing the value of accounting for body size, physical activity, and metabolic efficiency in diet-disease analyses via energy intake adjustment. Their publication has since been cited over 2,886 times and has inarguably advanced methodology for studying diet-disease associations, with most nutritional epidemiology studies standardly including some form of energy adjustment. However, there remains debate regarding the best scenarios and methods for energy adjustment. The goals of this commentary are to provide an updated review on factors that account for interindividual differences in energy intake, provide a balanced discussion regarding the considerations for or against adjustment for energy intake, and provide an updated examination of the commonly employed methods for the analysis of nutrient-disease associations. The principles of energy adjustment continue to be relevant nearly 25 years later, as it remains a critical method to account for potentially confounding interindividual variations in body size and physical activity.

Adherence to Mediterranean dietary quality index and risk of breast cancer in adult women: a case-control study

BACKGROUND

Breast cancer (BC) is the fifth most prevalent cause of cancer-related deaths in Iran. Given that the role of whole-diet on cancer risk is important, this study aimed to assess the association of MedDQI and breast cancer risk.

METHODS

This hospital-based case-control study was performed on 150 women with pathologically confirmed breast cancer within the period of less than 3 months. Controls were 150 apparently healthy that were matched by age. Dietary data was collected using a validated questionnaire. To examine participants' adherence to MedDQI, the MedDQI was created according to foods and nutrients highlighted or minimized in the MedDQI construction.

RESULTS

After adjusting for possible confounders, participants in the highest quartile of the MedDQI score had 55% lower odds of breast cancer than women in the bottom quartile (OR: 0.45, 95% CI: 0.21, 0.94, P trend: 0.02). Stratified analysis by menopausal status showed such association in postmenopausal women (OR: 0.24, 95% CI: 0.07, 0.8, P trend: 0.055) after controlling for age and energy intake.

CONCLUSION

The results showed an inverse association between adherence to the MedDQI and risk of breast cancer among Iranian women. More prospective studies are needed to confirm our results.

Consumption of “Diabetes Risk Reduction Diet” and Odds of Breast Cancer Among Women in a Middle Eastern Country

Background:

Given the role of insulin resistance in several cancers, we hypothesized that consumption of a diet that reduces insulin resistance might lower the risk of breast cancer.

Objective

The present study was designed to assess the association between consumption of “diabetes risk reduction diet” (DRRD) and odds of breast cancer among a large group of women in a Middle Eastern country.

Methods

This population-based case-control study enrolled 350 newly diagnosed cases of stage I-IV breast cancer and 700 age-matched apparently healthy individuals as controls. We collected dietary data via a validated 106-item Willett-format semi-quantitative dish-based food frequency questionnaire. A DRRD score was included based on 9 dietary factors (cereal fiber, coffee, nuts, whole fruits, ratio of polyunsaturated to saturated, trans fat, sugar-sweetened beverages, red and processed meat, and lower glycemic index). For food and nutrient items with a protective association with diabetes in earlier studies, participants were given the score as the quintile of that food item, but for food groups with unfavorable association with diabetes, we did vice versa. Total DRRD score ranged from 5 to 45.

Results

Mean age of cases and controls was 65.28 and 61.04 years. Mean BMI of patients with breast cancer and controls was 25.5 and 21.0. We found that individuals with the greatest adherence to the DRRD were 0.41 times less likely to have breast cancer than those with the lowest adherence (OR: 0.59; 95% CI: 0.38, 0.90, and P-trend = 0.002). Stratified analysis by menopausal status indicated a significant inverse relationship in postmenopausal women (OR: 0.57; 95% CI: 0.36–0.90), but not in premenopausal women (OR: 0.76; 95% CI: 0.19–2.96). Moreover, by BMI status, we found statistically significant inverse association between adherence to the DRRD and odds of breast cancer among normal-weight women (OR: 0.59; 95% CI: 0.36, 0.98) but not in overweight women (OR: 0.66; 95% CI: 0.31, 1.40). Conclusions: Significant inverse associations were found between adherence to DRRD and breast cancer, especially among postmenopausal and normal-weight women.

Systematic integrated analyses of methylomic and transcriptomic impacts of early combined botanicals on estrogen receptor-negative mammary cancer

Dietary botanicals such as the cruciferous vegetable broccoli sprouts (BSp) as well as green tea polyphenols (GTPs) have shown exciting potential in preventing or delaying breast cancer (BC). However, little is known about their impact on epigenomic aberrations that are centrally involved in the initiation and progression of estrogen receptor-negative [ER(−)] BC. We have investigated the efficacy of combined BSp and GTPs diets on mammary tumor inhibition in transgenic Her2/neu mice that were administered the diets from prepubescence until adulthood. Herein, we present an integrated DNA methylome and transcriptome analyses for defining the early-life epigenetic impacts of combined BSp and GTPs on mammary tumors and our results indicate that a combinatorial administration of BSp and GTPs have a stronger impact at both transcriptome and methylome levels in comparison to BSp or GTPs administered alone. We also demonstrated a streamlined approach by performing an extensive preprocessing, quality assessment and downstream analyses on the genomic dataset. Our identification of differentially methylated regions in response to dietary botanicals administered during early-life will allow us to identify key genes and facilitate implementation of the subsequent downstream functional analyses on a genomic scale and various epigenetic modifications that are crucial in preventing ER(−) mammary cancer. Furthermore, our realtime PCR results were also found to be consistent with our genome-wide analysis results. These results could be exploited as a comprehensive resource for understanding understudied genes and their associated epigenetic modifications in response to these dietary botanicals.

Correlations between Cancer Mortality Rates from Various Italian Regions

Death certification rates from 17 non-sexual and 4 sexual cancers were used to examine patterns of correlation between various cancers within the 20 Italian regions. A large number of strongly positive correlations emerged, reflecting the geographical distribution of cancer mortality in Italy which shows substantially higher rates for several common sites in northern areas. The most notable findings were the high positive correlations between various tobacco-related cancers in both sexes (however somewhat higher in males), the positive correlations between most intestinal sites and between a well defined group of other cancers including intestines in both sexes, breast and ovary in females and prostate in males, previously described in several widely heterogeneous populations. Various alcohol-related cancers showed high positive coefficients in males but not in females. Several suggestions which emerged from previous correlation studies but which generally lacked convincing biological or epidemiological consistency were not confirmed by the present data. Conversely, a few strong correlations emerged in the present study which are not explainable in terms of available knowledge of the causes of cancer, or obvious confounding. Though probably incidental, the existence of these correlations between cancers with widely heterogeneous or largely undefined etiology is still an indirect indication that these neoplasms are largely avoidable, since it is unlikely that the same genetic determinants are strongly associated with such different malignancies.

Meta-Analysis of Saturated Fatty Acid Intake and Breast Cancer Risk

The associations between saturated fatty acid (SFA) consumption and risk of breast cancer (BC) remains inconclusive. Therefore, we conducted this meta-analysis to determine the quantitative relations between dietary SFA intake and incidence of BC.Literatures published up to April 2015 were systematically screened through Pubmed and Web of Science. Relevant publication quality was evaluated by conducting the Newcastle-Ottawa scale. We used fixed effects models or random effect models to calculate the summary relative risks (RRs) and odds ratios (ORs), and conducted sensitivity analyses and evaluated the publication bias.We identified a total of 52 studies (24 cohort studies and 28 case-control studies), with over 50,000 females diagnosed with BC. The associations between dietary SFA intake and risk of BC were 1.18 for case-control studies (high vs low intake, 95% confidence interval [CI] = 1.03-1.34) and 1.04 for cohort studies (95% CI = 0.97-1.11). When restricted analyses to population-based studies, positive associations were observed for both cohort (RR [95% CI] = 1.11 [1.01-1.21]) and case-control studies (OR [95% CI] = 1.26 [1.03-1.53]). Additionally, for case-control studies, significant positive associations between higher SFA intake and BC risk were observed for Asian (OR [95% CI] = 1.17 [1.02-1.34]) and Caucasian (OR [95% CI] = 1.19 [1.00-1.41]), as well as for postmenopausal women (OR = 1.33, 95% CI: 1.02-1.73). In contrast, higher dietary SFA intake was not associated with risk of BC among premenopausal women, in cohort studies or hospital-based studies.A positive association between higher dietary SFA intake and postmenopausal BC risk was observed in case-control but not in cohort studies. More studies are warranted to confirm these findings.

Dietary fat intake in relation to lethal breast cancer in two large prospective cohort studies

Whether fat intake influences risk of developing more aggressive, lethal breast tumors is unknown. We evaluated intakes of total fat, specific types of fat, and cholesterol prior to diagnosis in relation to lethal breast cancer risk in 88,759 women in the Nurses' Health Study (NHS; 1980-2010) and 93,912 women in the Nurses' Health Study II (NHSII; 1991-2010). Diet was assessed every 4 years using a semi-quantitative food frequency questionnaire. Breast cancers were confirmed with pathology reports; deaths were confirmed by next of kin or the National Death Index. We defined lethal cases as women with invasive breast cancer who died of breast cancer. We pooled the cohorts and used multivariable Cox proportional hazards models. We identified 1,529 lethal breast cancer cases (1,279 in NHS and 250 in NHSII). Higher total fat intake was associated with a slightly lower lethal breast cancer risk (top vs. bottom quintile hazard ratio [HR] 0.85; 95 % CI 0.72, 1.01; p trend = 0.05). Specific types of fat were generally not associated with lethal breast cancer risk. For example, compared with those in the lowest quintile of saturated fat intake, those in the highest quintile had a HR of 0.98 (95 % CI 0.75, 1.26; p trend = 0.96). Among women diagnosed with breast cancer, pre-diagnosis fat intake was not associated with survival. Higher pre-diagnosis fat intake was not associated with greater risk of lethal breast cancer in these large prospective cohort studies, consistent with the weight of the evidence against a causal role for fat intake and breast cancer incidence.

Total energy intake and breast cancer risk in sisters: the Breast Cancer Family Registry

Energy restriction inhibits mammary tumor development in animal models. Epidemiologic studies in humans generally do not support an association between dietary energy intake and breast cancer risk, although some studies suggest a more complex interplay between measures of energy intake, physical activity, and body size. We examined the association between total energy intake jointly with physical activity and body mass index (BMI) and the risk of breast cancer among 1,775 women diagnosed with breast cancer between 1995 and 2006 and 2,529 of their unaffected sisters, enrolled in the Breast Cancer Family Registry. We collected dietary data using the Hawaii-Los Angeles Multiethnic Cohort food frequency questionnaire. Using conditional logistic regression to estimate the odds ratios (OR) and 95 % confidence intervals (CI) associated with total energy intake, we observed an overall 60-70 % increased risk of breast cancer among women in the highest quartile of total energy intake compared to those in the lowest quartile (Q4 vs. Q1: OR = 1.6, 95 % CI: 1.3-2.0; P (trend) < 0.0001); these associations were limited to pre-menopausal women or women with hormone receptor-positive cancers. Although the associations were slightly stronger among women with a higher BMI or lower level of average lifetime physical activity, we observed a positive association between total energy intake and breast cancer risk across different strata of physical activity and BMI. Our results suggest that within sisters, high energy intake may increase the risk of breast cancer independent of physical activity and body size. If replicated in prospective studies, then these findings suggest that reductions in total energy intake may help in modifying breast cancer risk.

Achievements and future of nutritional cancer epidemiology

We consider some of the earlier work and some recent results on diet and cancer (since the 2007 WCRF/AICR report on Diet and Cancer), discuss challenges facing nutritional cancer epidemiology, and consider the field from the perspective of the need to apply what we know in cancer control. We highlight 2 current difficulties; first, we are uncertain on the stage of carcinogenesis on which many nutritional factors act, second, we often do not know what dose of a nutritional factor is needed to achieve its expected protective effect in humans. Part of the difficulty is the measurement error associated with food frequency questionnaires. Calibration studies (as in the European Prospective Investigation on diet and Cancer) have helped to reduce this, and pooled studies have helped to clarify associations. However, there is too little work on new biomarkers of nutrition; with the new techniques available (especially proteomics, and metabolomics) it should be possible to identify more and better biomarkers that could be used in repeated blood or urine samples and give very good information on diet. In cancer control we need to determine how to reduce the prevalence of obesity and increase physical activity in populations, not whether they are causal factors. This could be achieved by community-based interventions linked to some of the new cohort studies being initiated. We conclude we have reached the stage in nutritional cancer epidemiology where we need to concentrate more on applying the lessons we have learnt, than in seeking new aetiological associations.

Energy intake and risk of postmenopausal breast cancer: an expanded analysis in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) cohort

Although animal experiments have consistently shown a positive relationship between breast cancer and energy intake, evidence from human studies remains inconclusive. In the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial cohort, 29,170 women, ages 55 to 75 years, who successfully completed a food frequency questionnaire (FFQ) at entry (1993-2001), were followed through 2007, and 1,319 incident breast cancers were ascertained (median time from FFQ completion to diagnosis, 4.4 years). Women in the highest quartile of energy intake, relative to the lowest, had modestly, but significantly, increased breast cancer risk [multivariate relative risk (RR), 1.21; 95% confidence interval (95% CI), 1.03-1.42; P(trend) = 0.03]. The inclusion of body mass index and physical activity in the model reduced risk slightly (RR, 1.18; 95% CI, 1.00-1.39; P(trend) = 0.07). However, in similar analyses using energy intake from a FFQ administered approximately five years after entry (27,428 women; 806 incident breast cancers; median time from FFQ completion to diagnosis, 2.7 years), women in the highest and lowest quartiles of energy intake had similar risk. When follow-up time after the first FFQ was divided into three 4-year periods, the multivariate RRs for high versus low energy intake increased from 1.21 to 1.37 to 1.55 with increasing time since dietary assessment. Although the divergent results for the two FFQs could be due to subtle questionnaire differences, our findings suggest a modest positive association between energy intake and postmenopausal breast cancer that strengthens with time since dietary assessment.

The role of dietary measurement error in investigating the hypothesized link between dietary fat intake and breast cancer--a story with twists and turns

The association between dietary fat and breast cancer is one of the most controversial hypotheses in nutritional epidemiology. In this editorial, the authors review the evidence from animal and human studies, including international correlation, case-control, cohort studies, intervention trials, and studies comparing dietary assessment instruments. The authors emphasize the importance of the role played by measurement error arising from assessing dietary habits using self-reported questionnaires, as it can distort estimated associations, not necessarily towards the absence of an association. They describe the twists and turns of the dietary fat and breast cancer debate that have revolved around this issue.

Association of energy intake and energy balance with postmenopausal breast cancer in the prostate, lung, colorectal, and ovarian cancer screening trial

Energy restriction remains one of the most effective ways known to prevent breast cancer in animal models. However, energy intake has not been consistently associated with risk of breast cancer in humans. In a prospective study, we assessed whether energy intake, body size, and physical activity each independently influence breast cancer risk in postmenopausal women and estimated the joint effect of combinations of these individual factors. As part of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, 38,660 women, ages 55 to 74 years and recruited from 10 centers in the United States during 1993 to 2001, were randomized to the screening arm of the trial. At baseline, the women completed a self-administered questionnaire, including a food frequency questionnaire. During follow-up from 1993 to 2003, 764 incident breast cancer cases were ascertained. Women in the highest quartile of energy intake (> or = 2,084 kcal/d) compared with those in the lowest quartile (<1,316 kcal/d) had a significantly increased risk for breast cancer [multivariate relative risk (RR), 1.25; 95% confidence interval (95% CI), 1.02-1.53; P(trend continuous) = 0.03]. Current body mass index (BMI) was also positively and significantly associated with risk (multivariate RR comparing >30 kg/m2 with <22.5 kg/m2, 1.35; 95% CI, 1.06-1.70; P(trend) = 0.01). Women with > or = 4 hours/wk of vigorous recreational physical activity had a significantly reduced risk of breast cancer compared with those who reported no recreational physical activity (multivariate RR, 0.78; 95% CI, 0.60-0.99; P(trend) = 0.15). None of these associations with individual energy balance measures was substantially confounded by the other two measures. When we estimated the joint effect of all three variables, women with the most unfavorable energy balance (the highest energy intake, highest BMI, and least physical activity) had twice the risk (RR, 2.10; 95% CI, 1.27-3.45) of women with the most favorable energy balance (the lowest energy intake, lowest BMI, and most physical activity). Although our estimates of absolute energy intake, based on a food frequency questionnaire, are imperfect, these results suggest that energy intake, in addition to BMI and physical activity may be independently associated with breast cancer risk. In addition, these three aspects of energy balance may act jointly in determining breast cancer risk.

Investigating the causes of vertigo in breast cancer survivors

The vertigo symptom in breast cancer survivors has rarely been mentioned. The aim of this study was to investigate the causes of vertigo in breast cancer survivors with vertigo. From May 1997 to April 2003, 36 consecutive female breast cancer survivors with vertigo underwent a battery of tests including physical examination, neurological examination, serum lipid profile, plain chest radiograph, whole body bone scan, liver sonography, audiometry, electronystagmography (ENG) and MRI scan. Based on these tests, the causes of vertigo were attributed to peripheral labyrinthine origin in 14 patients (39%) and central origin in 22 patients (61%) consisting of 11 cases of vascular insufficiency, eight of hyperlipidemia and three of posterior fossa metastases (8%). The latter included one case of cerebellopontine angle and two of cerebellum, accompanied by extracranial systemic metastases, e.g., of the lung, bone or liver. In conclusion, vertigo in breast cancer survivors warrants concern, especially in those with extra-cranial systemic metastasis accompanied by headache. In addition to 8% occurrence of posterior fossa metastasis, other possible causes for vertigo in breast cancer survivors consist of vascular insufficiency, hyperlipidemia and labyrinthine lesion.

Dietary fat and breast cancer risk revisited: a meta-analysis of the published literature

Animal experiments and human ecological studies suggest that dietary fat intake is associated with a risk of breast cancer, but individual-based studies have given contradictory results. We have carried out a meta-analysis of this association to include all papers published up to July 2003. Case–control and cohort studies that examined the association of dietary fat, or fat-containing foods, with risk of breast cancer were identified. A total of 45 risk estimates for total fat intake were obtained. Descriptive data from each study were extracted with an estimate of relative risk and its associated 95% confidence interval (CI), and were analysed using the random effects model of DerSimonian and Laird. The summary relative risk, comparing the highest and lowest levels of intake of total fat, was 1.13 (95% CI: 1.03–1.25). Cohort studies (N=14) had a summary relative risk of 1.11 (95% CI: 0.99–1.25) and case–control studies (N=31) had a relative risk of 1.14 (95% CI 0.99–1.32). Significant summary relative risks were also found for saturated fat (RR, 1.19; 95% CI: 1.06–1.35) and meat intake (RR, 1.17; 95% CI 1.06–1.29). Combined estimates of risk for total and saturated fat intake, and for meat intake, all indicate an association between higher intakes and an increased risk of breast cancer. Case–control and cohort studies gave similar results.

Body mass index, height and cumulative menstrual cycles at the time of diagnosis are not risk factors for poor outcome in breast cancer

Obesity, height and age at menarche have been shown to be risk factors for the development of primary breast cancer. However, their prognostic influence on breast cancer once it has presented is uncertain. The present study analysed 448 patients with primary breast cancer to determine whether or not body mass index (BMI), height and cumulative menstrual cycles at diagnosis are independent prognostic variables. The effects of all three variables on survival time and disease free interval were estimated. Of the 448 patients after a median follow up of 6 years, 190 (42%) developed recurrence and 162 (36%) had died. Body Mass Index and height could be calculated from available data in 403 patients and cumulative menstrual cycles in 388 patients. There was no evidence of an effect of BMI on survival time (P=0.99; hazard ratio=1.000; 95% Confidence Interval 0.968-1.034) or disease free interval (P=0.92; hazard ratio=1.002; 95% Confidence Interval 0.973-1.031). Similarly, height and cumulative menstrual years did not influence outcome in patients with primary breast cancer. However, nodal status and tumour size were both significant prognostic factors (P<0.001). The present study found no association between Body Mass Index, height and cumulative menstrual years and outcome in patients with primary breast cancer.

Vitamin D, calcium and prevention of breast cancer: a review

Several recent epidemiologic and experimental studies have suggested that decreased calcium and vitamin D intake and high dietary fat are associated with mammary gland carcinogenesis. Complete reduction or elimination of human exposure to environmental factors such as high-fat diets is inherently difficult to implement. Recent studies have begun to evaluate a possible role for increased dietary calcium and vitamin D in reducing the risk of colonic and mammary cancers, even in the presence of a high-fat diet. Studies from our laboratory recently found that decreased dietary calcium and vitamin D in a high-fat diet induced adverse changes in the mammary gland and several other organs, which were reversed by increasing dietary calcium and vitamin D; the findings further suggest a possible role for increased dietary calcium and vitamin D in the chemoprevention of these cancers.

Understanding meta-analysis in cancer epidemiology: dietary fat and breast cancer

Meta-analyses of the relationship between dietary fat and breast cancer risk using different methodologies have reported conflicting results. This investigation compares methodologic aspects of meta-analyses of patient data (MAP) with meta-analyses of data from the literature (MAL), and computes relative risk (RR) estimates from a random effects model using 28 published studies of dietary fat and breast cancer. MAP and MAL results compare closely when homogeneity is verified. When statistical homogeneity is rejected, a random effects model adjusting for study design and location is appropriate. The highest RR was found for case-control studies of European women (RR: 1.46), followed by North American case-control studies (RR: 1.25), case-control studies of women on other continents (RR: 1.23), cohort studies in Europe (RR: 1.20), and cohort studies in North America (RR: 1.02). The overall risk estimate in a MAL with heterogeneous studies should be interpreted only in a conditional model.

Perspectives on cancer prevention

Cancer prevention is a major component of cancer control, which also comprises screening, treatment, rehabilitation and palliative care. Preventive approaches need to be congruent with those adopted for other chronic diseases, with a major impact in reduction of incidence and mortality of many common cancers to be expected from smoking control and dietary modification. Increasing interest is now being paid to other environmental causes of cancer, and to gene-environment interactions. However, one of the major research needs remains the evaluation of better ways to convince people to make the necessary changes in their lifestyle that will reduce their risk of cancer.

Reproducibility and validity of a food-frequency questionnaire designed for use in girls age 7 to 12 years

This study focused on a food-frequency questionnaire (FFQ) designed to measure nutrient intake in girls aged 7 to 12 years, inclusive. The instrument's reproducibility and validity were assessed using food records (FRs) as gold standards of measurement. Log-transformed nutrient intake estimates were compared from two FFQs and between FFQs and FRs. Intraclass correlation coefficients measuring the reproducibility of the FFQ ranged from 0.11 (starch) to 0.69 (fiber). Intraclass correlation coefficients measuring agreement between FFQ and 14l-day FR data varied between 0.15 (starch) and 0.68 (vitamin B2) for the first, and between 0.06 (starch) and 0.95 (vitamin B1) for the second FFQ. FFQs were in the best agreement with FRs for the following nutrients: fiber, vitamin B1, vitamin B2, vitamin C, and beta-carotene. Joint classifications revealed that overall, 36% of subjects were similarly categorized by FFQ and FR, and 70% of those in the lowest or highest FR quartiles were were found in the lowest or highest FR quartiles were found in the lowest or highest two FFQ quartiles, respectively.

Serum vitamin E level in patients with breast cancer

In this study, the serum vitamin E (total tocopherol) levels in patients with breast cancer (n = 100) and healthy controls (n = 70) were measured. The mean values for vitamin E were found to be 0.44 mg/100 ml in breast cancer patients and 1.108 mg/100 ml in controls. In the statistical evaluation, the vitamin E levels in breast cancer patients are significantly lower than in the controls (P < 0.05). The influence of factors such as suckling period, age of first gestation, smoking status and dietary habits were also studied.

Cancer risks among female farmers in Sweden

There are few studies on cancer risks among female farmers, particularly on breast cancer and cancer in female genital organs. We have conducted a cohort study of cancer risk among 50,682 women with occupations in agriculture according to the Swedish 1970 census. The cohort was followed up in the nationwide, population-based, Cancer-Environment Register from 1 January 1971 until death or until 31 December 1987. Expected number of cases was based on annual cancer incidence in five-year age groups. The standardized incidence ratio (SIR) was computed as the ratio between observed and expected number of cases. A total of 4,474 cases of cancer were observed in the cohort from 1971 until 1987 cf 5,273 expected, resulting in a significantly decreased SIR of 0.85 (95 percent confidence interval [CI] = 0.82-0.87). SIR for breast cancer was significantly decreased (0.83, CI = 0.78-0.88), as was the SIR for cervix uteri (0.40, CI = 0.31-0.50). For the other female genital organs, SIR was close to one. Other cancer sites with significantly decreased SIRs were: colon (0.90, CI = 0.81-1.00); rectum (0.86, CI = 0.74-1.00); lung (0.46, CI = 0.37-0.57); kidney (0.81, CI = 0.68-0.97); urinary organs (0.57, CI = 0.45-0.72); connective tissue and muscle (0.62, CI = 0.39-0.95); and non-Hodgkin's lymphomas (0.78, CI = 0.63-0.96).

Dietary fat and breast cancer risks. An epidemiologic perspective

BACKGROUND

Breast cancer is one of the most important public health problems facing women in the United States and similar populations today. No readily modifiable risk factors for the disease have been conclusively identified, hence establishment of a positive association between fat intake and risk is of major public health importance.

METHODS

An evaluation of the strengths and limitations of epidemiologic studies addressing the postulated association between fat intake and breast cancer risk is presented. In light of this assessment, an evaluation of the results of ecologic and case-control studies has been conducted.

RESULTS

Of the three types of epidemiologic studies considered, ecologic studies provide the weakest evidence. Although case-control studies are more prone to bias than cohort studies, there is conflicting evidence as to the existence and magnitude of bias in previously conducted case-control studies. Ecologic studies and case-control studies support the existence of a positive association, particularly for saturated fat intake in postmenopausal women. However, given the methodologic limitations of these types of study and the more equivocal nature of evidence from cohort studies, it would be imprudent to interpret these associations as representing causality.

CONCLUSIONS

The totality of the epidemiologic evidence does not support the existence of a strong association between fat intake and breast cancer risk; however, the possibility of a weak association cannot be excluded. Even a weak association could be important in terms of public health. The most fruitful area for future research is likely to be the establishment of new cohort studies and the continued follow-up of existing cohorts, particularly if these could address diet at different times in life, for example, during adolescence.

Interrelationship between dietary lipids and calories and experimental mammary gland tumorigenesis

The purpose of this communication was to review and critique the studies designed to examine the interrelationship between dietary fat and calories in experimental rodent mammary gland tumorigenesis. The results of these studies clearly show that hyperalimentation of fat, either saturated or unsaturated, significantly stimulates this tumorigenic process. This has been demonstrated in an impressive array of carcinogen-induced, transplantable, spontaneous, and metastatic experimental rodent mammary gland tumor systems. The stimulatory effect of high levels of dietary fat appears to act primarily at the promotional stage of this tumorigenic process. Whether the mammary tumor stimulatory effect of high levels of dietary fat is a result of the metabolic activity of the fat per se or is due to an excessive energy (caloric) intake has been examined. Data obtained from the experimental studies that address this issue support the viewpoint that the mammary tumorigenic-enhancing activities of a high fat diet is, at least in part, through a caloric mechanism.

Alcohol and breast cancer. Where are we now and where do we go from here?

The alcohol-breast cancer hypothesis is important because (1) breast cancer is a major source of morbidity and mortality, (2) alcohol consumption is common, and (3) drinking is modifiable. Reports from more than 50 epidemiologic investigations of this hypothesis have now appeared. A recent metaanalysis of these studies indicates both a modest positive association between alcohol and breast cancer (an approximately 25% increase in risk with daily intake of the equivalent of two drinks) and a dose-response relation. Data suggest that risk increases with consumption of alcohol in general, regardless of beverage type. Several factors, including age, weight, and estrogen usage, have been shown to modify this relation in some studies. The authors discuss a series of methodologic issues in the study of alcohol and breast cancer. These include error in alcohol assessment, difficulties in evaluating small relative risks, and the potential for confounding. Several biologic mechanisms could account for an alcohol-breast cancer relation, with increasing attention being paid to a possible mediating effect of reproductive steroid hormones. Animal studies are a relatively recent development in this area; results have been mixed. Incorporation of more refined temporal, quantitative, and qualitative indicators of alcohol exposure in future epidemiologic studies would be valuable, as would further exploration of the endocrine and other metabolic effects of moderate alcohol consumption. The alcohol-breast cancer hypothesis remains intriguing, but causality has not been established.

Nutritional risk factors for breast cancer

The observation of large differences in breast cancer rates between countries has led to the hypothesis that excessive intake of dietary fat is an important risk factor for breast cancer in women. Case-control and prospective studies, however, generally have failed to show associations between dietary fat and breast cancer risk. There therefore is only weak evidence that modest reductions in fat intake (for instance to levels of 30% of caloric intake from fat) will reduce breast cancer risk. The possible benefits of lowering fat intake to levels substantially below 30% of calories will need to be tested in a randomized trial. In the meantime, the possible roles of micronutrient imbalances and childhood nutritional factors need to be studied better. Obesity is related to breast cancer in a complex way that suggests that a hormonal correlate of excessive body weight might affect breast cancer growth and metastasis. The potential benefit of intentional weight loss as an adjunct breast cancer treatment deserves further study. Many studies have suggested that drinking alcohol, even at modest levels, might increase breast cancer risk. Because the potential benefits of modest levels of alcohol for cardiovascular disease may outweigh the risk for breast cancer, recommendations for total alcohol abstinence may be premature for women with an average breast cancer risk. Women at unusually high risk for breast cancer who have a lower-than-average risk for cardiovascular disease, however, might make an informed decision to abstain from alcohol intake. Following current dietary advice to increase the amount of fruits, vegetables, and whole grains in the diet while reducing fats is certainly prudent for women to reduce their risk of several chronic disease, but current data points to the somber conclusion that such changes probably will have little effect on breast cancer risk.

The association between breast cancer and diet and other factors

To explore the effects of diet and other factors on breast cancer development, a case-control study was conducted in Tianjin between 1986-87. After adjusting for confounding factors, it was found that factors associated with increased risk of breast cancer included --early age at menarche; late age at menopause; late age at first birth; high Qutelet's index; histories of breast wound, disease and benign tumor; and a family history of malignant tumor, high fat, high calorie, low vegetable intake; elevated serum cholesterol and LDL-cholesterol; and lower levels of serum HDL-cholesterol and whole blood selenium.

Vitamin D adequacy: a possible relationship to breast cancer

(1) Low levels of dietary calcium and vitamin D, biochemically interrelated, increase the promoting action of high dietary fat on chemically induced mammary carcinogenesis in animal studies. (2) High dietary fat increases mammary epithelial cell proliferation, particularly the "hormonally driven" hyperproliferation during breast growth and development in young animals. Increased dietary calcium (and probably vitamin D) lessens the increase of proliferation induced by high fat. These data, although limited, suggest that the maximum effect of diet (high fat increase, as well as calcium and vitamin D modulation) on eventual breast cancer may be during puberty, and adolescence, when the mammary gland is actively growing and developing. (3) An inverse epidemiological correlation has been developed between sunlight availability as a source of vitamin D and the risk of breast cancer in the U.S. and Canada. (4) Current vitamin D and calcium dietary intake in the U.S. is far below the RDA in all female age groups, particularly for the elderly. (5) Reduction of breast cancer risk, and simultaneously osteoporosis, might be achieved by increasing dietary intake of calcium and vitamin D to RDA levels. This may be particularly applicable to females during puberty and adolescence.

Assessment of the reliability of a diet history questionnaire

The purpose of this study was to estimate the reliability of a self-administered food frequency questionnaire developed at the National Cancer Institute (NCI) (Bethesda, MD). Food intake information was collected from 48 women with breast cancer and 50 women who had a familial breast cancer risk. These women were participants in a long-term investigation of diet and breast cancer at the Ohio State University (Columbus, OH). Pearson correlation coefficients were obtained for 29 nutrients. The effect of time between questionnaires, age, weight, and caloric intake was also examined. The results showed moderate reliability coefficients for most of the nutrients (r = 0.5-0.8). For the majority of nutrients, the women with breast cancer had higher coefficients than did the high-risk women. High-risk women with shorter elapsed time periods between the first and second questionnaire had higher reliability coefficients as did women who consumed fewer calories. Age and weight (standardized by height) showed no effect on reliability. Recommendations for improving the NCI questionnaire in addition to using it as a standard method of measuring food intake are discussed.

Alcoholic beverage consumption in relation to risk of breast cancer: meta-analysis and review

The objective was to evaluate the association between alcohol consumption and risk of breast cancer. Data from 38 epidemiologic studies on alcohol consumption in relation to risk of breast cancer in women were included in a meta-analysis. A qualitative literature review also was conducted. The results showed strong evidence of a dose-response relation; however, the slope of the dose-response curve was quite modest. For example, daily consumption of one alcoholic drink was associated with an 11 percent increase (95 percent confidence interval, seven to 16 percent) in the risk of breast cancer compared with nondrinkers. An explanation for the marked variation in results across studies was not found. The modest size of the association and variation in results across studies leave the causal role of alcohol in question. The evidence that alcohol consumption affects the risk of breast cancer, however, appears to be growing stronger.

Clinical management of women at increased risk for breast cancer

A large number of women in the population are at risk for the development of breast cancer. Methods now exist to accurately assess risk and to provide quantitative estimates of the chance of a woman developing breast cancer in her lifetime. Histologic assessment of premalignant breast pathology aids in the evaluation of risk. The availability of primary chemoprevention clinical trials reduces the number of indications for prophylactic mastectomy. Women at risk for breast cancer and women who have had a malignant lesion at another anatomic site have an increased risk for new cancers at multiple sites. We propose screening strategies based on epidemiologic information about the risks of these diseases and on the predictive value of the available screening tests. The merits and inadequacies of specific management strategies are considered. We review the risks and benefits of estrogen replacement therapy for women at increased risk for breast cancer and consider the ethical implications of both risk assessment and the various interventions.

A meta-analysis of studies of dietary fat and breast cancer risk

There is strong evidence that breast cancer risk is influenced by environmental factors, and animal experiments and human ecological data suggest that increased dietary fat intake increases the incidence of the disease. Epidemiological evidence on the relationship of dietary fat to breast cancer from cohort and case control studies has however been inconsistent. To examine the available evidence we have carried out a meta-analysis to summarise quantitatively the large published literature on dietary fat in the aetiology of breast cancer. After assembling all of the published case control and cohort studies, we extracted the relative risk in each study that compared the highest to the lowest level of intake. We then calculated a summary relative risk for all studies. The summary relative risk for the 23 studies that examined fat as a nutrient was 1.12 (95% CI 1.04-1.21). Cohort studies had a summary relative risk of 1.01 (95% CI 0.90-1.13) and case control studies a relative risk of 1.21 (95% CI 1.10-1.34). Summary estimates of risk for specific types of fat excluded unity for only saturated fat. For the 19 studies that examined food intake, the summary relative risks were 1.18 (95% CI 1.06-1.32) for meat, 1.17 (95% CI 1.04-1.31) for milk, and 1.17 (95% CI 1.02-1.36) for cheese. Summary relative risks for total fat intake were examined for several potential modifying factors. Regression analysis showed that European studies were more likely than studies done in other countries to show an increased relative risk associated with dietary fat and breast cancer, after taking into account potential modifying factors that included study design and quality.

Role of nutrition in women's health: diet and breast cancer

Breast cancer, which is the most frequently diagnosed malignancy in women today, remains a major threat. As the incidence increases at 1% to 2% annually, breast cancer strikes about 182,000 US women each year and kills 46,000. Known risk factors, such as age, early menarche, late age of first pregnancy, late menopause, family history, and obesity, account for only 40% to 50% of breast cancer cases. Consequently, the etiology of 50% to 60% of cases is unknown. Perhaps no area is more controversial than the link between nutrition and cancer, in particular the association between dietary fat and the development of breast cancer. Findings from animal research and international correlation studies indicate a causal relationship between fat intake and breast cancer. A recent analysis of 12 case-control studies among postmenopausal women also showed a 50% increase in relative risk among women ingesting high intakes of saturated fat. Furthermore, analyses of postmenopausal women in Hawaii estimated that 10% to 20% of breast cancer could be prevented by notably decreasing saturated fat intake. Nevertheless, epidemiologic studies (case-control and cohort) give conflicting results regarding the causal relationship between fat intake and breast cancer. The fact that these studies have failed to consistently show a significant association between dietary fat and breast cancer risk may be attributable to the difficulty of collecting accurate dietary information and other methodologic limitations. Findings are also limited by the lack of data on the influence of a high-fat diet during childhood.(ABSTRACT TRUNCATED AT 250 WORDS)

A rationale for dietary intervention in postmenopausal breast cancer patients: an update

In 1982, we proposed a large-scale randomized prospective trial to test the hypothesis that decreasing dietary fat intake from 38% to 20% of total calories would increase the disease-free interval and/or five-year survival rate for postmenopausal breast cancer patients. We now review new evidence from epidemiological studies, laboratory animal model studies, and preliminary feasibility trials that has accumulated over the past decade, in support of such a trial, and suggest that a more appropriate dietary goal is a reduction in fat intake to 15% of total calories.

Polyunsaturated fatty acids in serum phospholipids and risk of breast cancer: a case-control study from the Janus serum bank in Norway

We have tested the hypothesis that specific polyunsaturated fatty acids (PUFA) of the n-3 and n-6 families, as measured in serum phospholipids, are negatively associated with the risk of breast cancer. The study is based on serum samples from women who have donated blood to the Janus serum bank at the University Hospital in Oslo, Norway. It consists of sera from 87 women who developed breast cancer (cases) subsequent to blood donation and 235 women who were free of any diagnosed cancer (controls), but were of similar age and had similar blood storage time as the cases. We measured fatty acids (monounsaturated, polyunsaturated and saturated) in serum phospholipids, and made comparisons between cases and controls. The results showed that there was an inverse relation between the n-6 PUFA linoleic acid (18:2n-6) and risk of breast cancer, but this association was restricted to women who were 55 years and younger. In this age group, the relative risk (odds ratio) of women in the highest quartile of linoleic acid was 0.4 (95% confidence limits, 0.2 and 1.0) compared with women in the lowest quartile, and there was a negative trend over quartiles of linoleic acid (Mantel's chi for trend = -2.49, P < 0.02). No association was noted between the n-3 PUFA of marine oil origin and breast cancer risk. If the measured concentration of linoleic acid in serum phospholipids reliably reflects dietary intake, these data suggest that linoleic acid in the diet may decrease breast cancer risk among women at premenopausal and perimenopausal age. No similar association with n-3 unsaturated fatty acids was observed. It is noteworthy that none of the measured fatty acids (saturated or unsaturated) showed a positive association with breast cancer risk.

Tamoxifen reduces serum insulin-like growth factor I (IGF-I)

Antiestrogens are widely used in the management of hormonally responsive breast cancer in both adjuvant and palliative settings, and are currently being evaluated as chemopreventive agents. The classical mechanism of action of these drugs involves inhibition of estrogen-stimulated neoplastic cell proliferation by blockade of estrogen receptors present on breast cancer cells. This paper reviews recent clinical and laboratory data that suggest that the commonly used antiestrogen tamoxifen also acts to reduce serum IGF-I levels. Estrogens appear to play a permissive role in growth hormone (GH) release by the pituitary gland and GH is known to stimulate IGF-I expression by hepatocytes. It is therefore possible that blockade of estrogen receptors in the hypothalamic-pituitary axis by tamoxifen interferes with GH release, leading to reduced hepatic IGF-I expression. In view of results suggesting that IGF-I is a more potent mitogen than estradiol for breast cancer cells and data demonstrating a positive correlation between estrogen receptor level and IGF-I receptor level of breast cancer cells, the IGF-I lowering effect of tamoxifen may contribute to the cytostatic activity of the drug. The interrelationships between steroid hormone physiology and IGF-I physiology may have relevance to a variety of commonly used treatments for hormonally responsive cancers.

A randomized controlled trial of dietary fat reduction: the retention of subjects and characteristics of drop outs

We have examined the feasibility of carrying out a randomized controlled trial of dietary fat reduction in women at increased risk for breast cancer. The randomization was either to a control group who were taught the principles of balanced nutrition, but were not counselled to change their fat intake, or to an intervention group who were taught to reduce their dietary fat intake to 15% of total calories from a baseline average of 35% of calories. Potentially eligible subjects were women attending a breast diagnostic clinic who had the mammographic pattern of dysplasia. Subjects were recruited by letter from their referring surgeon followed by a telephone call. Subjects interested in participating in the study then entered by one of two phases. In Phase I, the study was explained, informed consent sought and willing subjects randomized to the intervention or control group. Using this procedure 227 subjects were randomized and 48 (21%) dropped out of the study in the 12 months following randomization. (A drop out was defined as a subject who persistently failed to keep appointments and provide nutrient data.) Of these drop outs, 30 (63%) occurred at or soon after randomization. A modified procedure of entry was then adopted in which subjects interested in the study were first taught the procedures involved, including keeping food records and clinic appointments, and were then asked to provide consent and randomized. Two hundred and eighty subjects were enrolled using this modified procedure and 25 (9%) have dropped out in the 12 months following randomization.(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary fat, calories, and mammary gland tumorigenesis

In this communication, a vast array of studies designed to examine the relationship between dietary fat and experimental mammary gland tumorigenesis was reviewed and critiqued. It is clear, as reported by many laboratories, that as the fat content of the diet is increased from a low or standard level to a high level, a consistent and substantial increase in the development of rodent mammary gland tumors is observed. The longer the duration the high-fat diet is fed, the greater the enhancing effect on tumorigenesis. Furthermore, the stimulatory effect of a high-fat diet is observed even when fed commencing late in an animal's life. A multitude of studies also have provided evidence that the type of fat can markedly influence the development of rodent mammary gland tumors. In general, high dietary levels of unsaturated fats (e.g., corn oil, sunflower-seed oil) stimulate this tumorigenic process more than high levels of saturated fats (e.g., beef tallow, coconut oil); diets rich in certain fish oils (e.g., Menhaden oil, Max EPA) are often the most inhibitory to this tumorigenic process. Importantly, however, supplementation of saturated fat or fish oil diets with modest amounts of unsaturated fats, e.g., corn oil, often negates the mammary tumor inhibitory activities of these fats. Thus, rather extreme differences in the types of fat are required for a differential in mammary gland tumorigenesis; common proportionate blends of different fats of animal, plant, and/or fish origin are often unable to differentially influence this tumorigenic process. Diets rich in monoenoic fatty acids, e.g., those containing high levels of olive oil, have been examined in a number of studies; results from these studies have been inconsistent. A number of reports suggest that the increase in development of mammary tumors in rodents fed a high-fat diet, compared with those fed a low-fat diet, is due to specific metabolic activities of the fat per se, activities independent of a caloric mechanism. Careful analysis of these reports suggest that such a conclusion may not be totally warranted. Indeed, persuasive evidence is accumulating indicating that the major mammary tumor development enhancing activities of a high-fat diet may be via a caloric (energy) mechanism. Caloric restriction, even in animals fed a high-fat diet, significantly suppresses mammary tumor development. Even mild caloric restriction (e.g., 12%) can significantly suppress development of mammary tumors in rodents.(ABSTRACT TRUNCATED AT 400 WORDS)