Alcohol consumption and risk of breast cancer

Estrogen, alcohol and breast cancer risk

Estrogen replacement has been used for many years to reverse the hypoestrogenic symptoms of menopause and prevent osteoporosis. Studies have found that estrogen replacement also decreases cardiovascular risk. In addition, social use of alcohol has been found to decrease cardiovascular risk. Therefore, both estrogen replacement therapy and alcohol use have been proposed to have cardiovascular benefits, and are often used in combination. Epidemiologic evidence indicates that estrogen replacement therapy after menopause increases breast cancer risk. Regular alcohol consumption is also associated with increase in risk. However, interactions between the two are poorly understood. In addition, if alcohol alters circulating estrogen levels in estrogen users, this may have implications in terms of altering the risks:benefit ratio of estrogen replacement in an undesirable direction. For example, there are data suggesting that the use of both alcohol and estrogen may increase breast cancer risk more than the use of either one alone. Data support both acute and chronic effects of alcohol in raising circulating estrogen levels in premenopausal women on no hormonal medications. In postmenopausal women studies focusing on acute effects of alcohol on estrogen metabolism indicate that alcohol has a much more pronounced effect in women using estrogen replacement than in those who do not. Studies evaluating chronic effects of alcohol ingestion on circulating estrogens in postmenopausal women are needed.

The association between alcohol and breast cancer: popular press coverage of research

OBJECTIVES

This study was undertaken to examine popular press reports of the association between alcohol and breast cancer.

METHODS

Articles from scientific journals and stories from newspapers and magazines published from January 1, 1985, to July 1, 1992, were retrieved from six on-line databases. Lay press stories were analyzed to determine which medical articles were publicized and what information was reported.

RESULTS

Fifty-eight scientific articles on the relationship of alcohol and breast cancer were found, and 64 newspaper and 23 magazine stories were retrieved. The press cited 11 studies, 19% of those published during the study period. Three studies were featured in 77% of popular press stories. No scientific review articles were reported. Behavioral recommendations were given to the public in 63% of stories.

CONCLUSIONS

The vast majority of scientific studies on alcohol and breast cancer were ignored in press reports. We encourage researchers and the popular press to give the public a broader understanding of public health issues.

Mental and physical health consequences of alcohol use in women

Chronic consumption of alcohol in levels typically consumed by alcoholic women clearly produces adverse health consequences, including a shorter life expectancy. The health consequences of alcohol use appear to depend on the characteristics of the person consuming the alcohol (genetic vulnerability to particular diseases, the particular point in the life span when the majority of the alcohol is consumed, and the pattern of consumption typical for that individual). For adolescence and young adulthood, emphasis is placed on increased rates of accidental and suicidal mortality. For middle age, breast cancer risk and risk for developing osteoporosis is discussed. Finally, use of alcohol alone and in combination with psychoactive drugs presents special problems for older women. Other specific adverse effects of alcohol are reviewed with respect to gender differences in cardiovascular, hepatological, and neuropathological outcome, as well as with respect to HIV/AIDS. Psychiatric comorbidity and domestic violence are also discussed with respect to gender differences.

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.

Cancer morbidity in alcohol abusers

Data on the association between alcohol abuse and cancer morbidity are scarce in large cohorts of non-hospitalised alcoholic men and women. Of 18,368 alcohol abusers who entered an outpatient clinic in Copenhagen during 1954-87, 18,307 were followed and their cancer incidence was compared with that of the total Danish population. On average the 15,214 men were observed for 12.9 years and the 3,093 women for 9.4 years. The overall morbidity of cancer was increased significantly. Of the men, 1,441 developed cancer [relative risk (RR) = 1.6; 95% confidence interval (CI) = 1.5-1.7], while 182 women did (RR = 1.5; 95% CI 1.3-1.8). Significantly increased incidences were found of cancer in the tongue, mouth, pharynx, oesophagus, liver, larynx, lung and pleura and secondary cancer. The women had significantly increased risk of cervical cancer (RR = 2.0; 95% CI 1.2-3.0). The men developed prostatic cancer significantly more frequently than expected (RR = 1.4; 95% CI 1.2-1.8). The risk of melanomas (RR = 0.5; 95% CI 0.2-0.8) was significantly lower than expected. The relative risks of cancer of the stomach, pancreas, kidney and endocrine system were only slightly increased. The study group did not develop more colonic (RR = 1.0; 95% CI 0.8-1.3) or rectal cancer (RR = 1.0; CI 0.7-1.3) than expected. The risk of breast cancer in women was slightly increased (RR = 1.3; 95% CI 0.9-1.7), but not statistically significant. Thus, the associations between alcohol and cancer of the upper digestive and respiratory tract and the liver are confirmed. In addition, this study indicates an increased occurrence of cancer of the prostate gland, pleura and uterine cervix in alcohol abusers.

Alcoholic beverages and breast cancer: some observations on published case-control studies

We identified 38 case-control studies investigating possible associations between alcoholic beverage consumption and cancer of the female breast. Each study was characterized according to design features such as: control type (hospital or community based), risk factors controlled for, matching strategy, and statistical power. We examined the effect of these design variables on several outcome variables including identification of any significant elevation in odds ratio and characterization of any dose-response effect. The major finding of this study is that of a striking difference between hospital and community based controlled studies with respect to (1) the level of any estimated dose-response effect, and (2) the finding of statistically significant elevations in odds ratios at levels of consumption below 4 drinks per week. In summary, the generally weak associations reported in these case-control studies along with the measurement and/or selection biases implied by our findings would lead one to the conclusion that present evidence does not support a causal association. This conclusion seems to be in accord with results from cohort studies and with similar conclusions from several other reviews.

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.

Recall and selection bias in reporting past alcohol consumption among breast cancer cases

Recall and selection bias are well-recognized potential problems in case-control studies of alcohol and cancer, but few analyses have attempted to assess the direction and the magnitude of these potential biases. We thus examined alcohol consumption in relation to risk of breast cancer using dietary questionnaires administered both before and after the diagnosis of breast cancer in the Nurses' Health Study (United States). Among cohort members who completed a dietary questionnaire in 1986 and who were free of cancer, 616 were diagnosed with breast cancer during follow-up to December 1989. These cases and 1,277 controls (a random sample of cohort members who did not develop cancer up to 1990) then were sent another questionnaire inquiring about their diet in 1985. Four hundred and ninety-four cases (80.2 percent) and 999 controls (78.2 percent) responded to the second questionnaire. The analysis based on the prospective (1986) questionnaire demonstrated an elevated risk of breast cancer among women who drank 30 or more g of alcohol daily (about two drinks) relative to nondrinkers (odds ratio [OR] = 1.55, 95 percent confidence interval [CI] = 1.01-2.39). The analysis based on the retrospective questionnaire also indicated a similar but slightly attenuated elevation of risk of breast cancer among women who drank at least 30 g daily (OR = 1.42, CI = 0.85-2.40). In these data, bias due to selection and recall had only minor effects on reported intake of alcohol consumption.

Alcoholic beverage consumption and risk of breast cancer in Spain

The relation between alcoholic beverage consumption and risk of breast cancer was examined. We used data from a population-based, case-control study that included almost all incident cases occurring in five Spanish regions from February 1990 to July 1991. A total of 762 women between 18 and 75 years of age, with a histologically confirmed, first diagnosis of breast cancer, were compared with 988 control women. Alcoholic beverage intake was measured by an interviewer-administered, semiquantitative food-frequency questionnaire. We used 'nondrinkers' as the reference category and divided the remainder into four categories according to alcohol intake. The multiple logistic analyses included not only alcohol intake but also possible confounding factors such as total caloric intake, age, socioeconomic status, and reproductive and medical histories. Even at moderate levels of alcohol intake (less than 8 g/day), a 50 percent increase in risk of breast cancer was found. The trend across categories of intake was statistically significant for wine and distilled drinks, as well as total alcohol intake. Consumption of 20 g or more of alcohol per day was associated with a 70 percent elevation in breast cancer risk compared with that of nondrinkers (adjusted relative risk (RR) = 1.7, 95 percent confidence interval = 1.3-2.3). Although the magnitude of the RR observed in our study was modest, our findings provide further support for a positive association between alcohol consumption and risk of breast cancer.

Do alcohol intake and mammographic densities interact in regard to the risk of breast cancer?

BACKGROUND

The effect of alcohol intake on mammographic densities and the possible interaction between these two factors in regard to the risk of breast cancer were assessed using information from the Breast Cancer Detection and Demonstration Project.

METHODS

Mammograms taken during the first year of screening for patients whose breast cancer was detected in the 5th year of follow-up (n = 266) and their matched controls (n = 301) were blindly assessed for the percent of mammographic densities, which were measured by planimetry.

RESULTS

Among controls, alcohol intake was weakly, positively associated with the percent of mammographic densities (Spearman rank correlation coefficient, 0.09), although the association may have been the result of chance (P = 0.12). After adjustment for confounding factors, the lifetime alcohol intake did not appear to modify the effect of the percent mammographic densities on the risk of breast cancer (P for the interaction, 0.09).

CONCLUSIONS

Longitudinal studies and larger case-control studies should be conducted to assess the relationship between diet and changes in mammographic densities further.

Alcohol and breast cancer: a review

This paper reviews the major studies on the possible relationship between drinking alcohol and breast cancer. The majority of these studies show some association between levels of alcohol consumption and breast cancer. However, the evidence of a causal link is lacking. A number of problems in interpreting the data are discussed. Given the high incidence of breast cancer in many countries, this is an important area. However, the imputed role of alcohol must not be exaggerated, particularly if this means that other more important factors in the equation fail to be examined.

Alcohol and breast cancer risk--putting the current controversy into perspective

The potential association of alcohol intake with breast cancer risk is currently being debated in the literature and a clear consensus of opinion has not emerged. Clarification of the issues surrounding this controversy would be helpful in developing recommendations for the general public regarding alcohol use. A review of the available evidence regarding the association of alcohol with breast cancer is presented followed by an application of the Bradford Hill criteria for causal inference to this data to examine the existence and nature of the association of alcohol with breast cancer risk. Results of published studies demonstrated a weak association of alcohol with breast cancer risk that was consistent only for relatively high levels of intake (more than 1 or 2 drinks daily). Increasing daily intake was associated with increased risk, but the association was not linear. Criteria relating to temporality and analogy to other causal associations were satisfied while inconsistent evidence was available for those relating to epidemiologic and biologic sense. The criterion for specificity was not satisfied and no experimental evidence was available. It is concluded that insufficient evidence exists to support a causal association of alcohol consumption with breast cancer risk. Further research is recommended to resolve conflicting evidence and to provide additional evidence where needed. In the meantime, recommendations that women should reduce their consumption of alcohol beyond existing guidelines to modify breast cancer risk are probably premature.

Alcohol consumption and the risk of breast cancer: a report from the Tecumseh Community Health Study

The relationship between prior alcohol consumption and the risk of breast cancer was studied in 1954 women in the Tecumseh Community Health Study (TCHS) who entered the cohort in 1959-1960 and were followed potentially for 28 years. The mean alcohol consumption at baseline was 0.89 (SD 2.2) oz/week for premenopausal women and 0.85 (SD 2.2) oz/week for postmenopausal women. Only 25% of the cohort consumed more than 0.5 oz of ethanol/week or about 1.6 g/day. The adjusted relative risks (RRs) for breast cancer associated with the use of ethanol vs never drinking were 0.93 (95% CI, 0.40-2.18) for ex-drinkers, 1.08 (95% CI, 0.64-1.82) for 0- less than 1 drink/day, 1.23 (95% CI, 0.49-3.10) for 1- less than 2 drinks/day and 1.12 (95% CI, 0.25-5.01) for greater than or equal to 2 drinks/day. There were only 37 subjects in the group at the highest level of consumption (greater than or equal to 2 drinks/day). There was no significant interaction between alcohol and the period of onset of breast cancer (premenopausal or postmenopausal). In the TCHS, alcohol consumption generally at levels not exceeding 2 drinks/day, was not significantly associated with an increased risk of breast cancer. Although we have found little excess risk associated with alcohol consumption, the wide confidence intervals summarized above are not inconsistent with previously published reports that have suggested a modest positive association.

Is alcohol a carcinogenic risk?

Consumption of alcoholic beverages has been implicated as a risk factor for the development of various cancers including oesophageal, oral, pharyngeal, laryngeal, liver and breast cancers. This article is a commentary on an earlier paper entitled 'Alcohol: a carcinogenic risk?' which challenges some of the evidence relating alcoholic beverage consumption to risk for these cancers. In the course of commenting on this paper, evidence is reviewed which shows a relationship between these cancers and consumption of alcoholic beverages, which is often found to be dose-related.

What can a woman do about her risk of dying of breast cancer?

Every day, American women are told that one in ten will develop breast cancer, and some groups perceive their risk to be so high as to justify immediate bilateral mastectomy. Many associations with breast cancer have been identified, including a history of benign breast diseases, in situ carcinoma, a family history of breast cancer, prolonged menstruation as a result of early menarche or delayed menopause, few or late pregnancies, excessive alcohol intake, obesity, and possibly the use of estrogens as oral contraceptives or postmenopausal replacement therapy. In spite of these associations, our understanding of either the cause(s) of breast cancer or the sequence of events leading to a diagnosis of breast cancer is still inadequate to make global public health recommendations regarding life style--or even to initiate well-designed studies. The epidemiologic evidence strongly suggests, however, that events relatively early in a woman's life are more important than later events, even though most of the risk of developing breast cancer will be expressed after the age of 75. Possibly one of the greatest contributions we can make to our patients' welfare is to share the knowledge that the risk of dying of breast cancer is considerably smaller than the risk of developing breast cancer; that the risk of early death from breast cancer rarely exceeds 10% in even the highest risk groups; and that the life styles most likely to reduce the risk of cardiovascular disease and other scourges of womankind are also those most likely to reduce the risk of developing breast cancer.

Alcohol consumption and breast cancer

Epidemiologic studies of the relationship of alcohol consumption and breast cancer are generally in support of a direct association, although they are not entirely consistent. Studies supporting this finding have come from many countries around the world and from many investigators working with different study designs and types of populations. Ten of 16 case-control studies, and five of six cohort studies have produced results supporting a positive association. When evaluated together through techniques such as meta-analysis, these studies suggest that there is a 50% increase in breast cancer risk for women who average between one and two drinks per day. All types of alcoholic beverages seem to increase the risk, but there is little agreement between studies on dose-response relationships. No biologic explanation for alcohol's possible role in breast carcinogenesis is yet known, but several hypotheses have been advanced. In the absence of any effective method of primary breast cancer prevention, and because current risk factors explain so little of the incidence of this common cancer, alcohol consumption is of potential importance from both public health and etiologic perspectives. The possible protective effect of moderate alcohol consumption on heart disease should be considered when assessing the risks of this level of consumption on breast cancer.

Racial and age differences in multiple primary cancers after breast cancer: a population-based analysis

The occurrence of multiple primary cancers was evaluated among 17,944 white and black female residents of Metropolitan Detroit diagnosed with breast cancer between 1973 and 1983. Invasive second primary cancers were diagnosed among 1106 of these women, almost twice the expected number. Subsequent in situ cancers were detected four times more often than expected. Fifty-six percent of the subsequent invasive cancers were of the breast (Standardized Incidence Ratio, SIR = 3.80). Black women experienced higher risk of subsequent breast cancers (SIR = 5.30) than white women (SIR = 3.62). Highest risk was seen among women first diagnosed before age 40 (SIR for black women = 26.15, SIR for white women = 10.87) and within five years of initial diagnosis. These findings suggest that young breast cancer patients, especially black women, are at high risk of developing a second primary breast cancer soon after their initial diagnosis and should be under continued medical surveillance. The occurrence of multiple primary breast cancers among young women suggests a genetic component to risk. Identification of this subpopulation would be useful in the study of molecular and genetic markers for cancer. Subsequent colon (SIR = 1.24) and cervical (SIR = 1.54) cancers also were diagnosed significantly more often than expected, as were ovarian cancers among white women (SIR = 1.45). These findings are consistent with common etiologic factors associated with these cancers.

Relationship between alcohol consumption and breast cancer morbidity rates in Western Australia, 1971--1984

Per adult (greater than or equal to 15 years) consumption of beer, wine, spirits and absolute alcohol for a 14-year period (1971--1984) was related to female breast cancer morbidity rates in Western Australia. Mann-Whitney U-tests showed that during the 7 years of highest wine consumption the highest rates for breast cancer occurred for females aged 30--59 years, but for women over 60 years of age the result was insignificant. The findings are consistent with a number of previous studies which have shown a positive association between alcohol consumption and increased risk of breast cancer.

A case-control study of breast cancer and alcohol consumption habits

A population-based case-control study was conducted to investigate the contribution of alcohol consumption during the early adult years (ages 18-35 years) and later adult years (older than age 35) to breast cancer risk. Alcohol consumption histories were obtained by questionnaire from 277 breast cancer cases, 372 population controls, and 433 controls with cancer of sites other than breast. Alcohol exposure during both age periods was significantly greater for breast cancer cases, but risks, estimated by maximum likelihood odds ratios, were highest for alcohol consumption frequency during the early adult period. Age-adjusted odds ratios and 95% confidence intervals (CI) for breast cancer risk and early age drinking (10 versus 0 drinks/week) were 2.2 (95% CI = 1.34, 3.5), relative to the population controls and 2.0 (95% CI = 1.3, 3.1) relative to the cancer controls. Based on later-age drinking of ten versus zero drinks/week, odds ratios were 1.8 (95% CI = 1.3, 2.6) and 1.6 (95% CI = 1.2, 2.2) relative to the population and cancer controls, respectively. The risk estimates were not altered by introduction of the following covariates into the analyses: mother with breast cancer, family status, education, body mass index, smoking, supplemental hormone use, and diet.

Alcohol consumption in a case-control study of breast cancer in southern France

The effect of alcohol consumption on breast cancer risk was investigated in a hospital-based, case-control study of 808 patients (349 cases and 459 controls) in Montpellier (France). Semi-quantified diet history including beverage consumption as well as relevant medical and personal characteristics were assessed by interview. A dose-rate relationship for total alcohol consumption was found with unadjusted odds ratios ranging from 1.8 (95% CI 1.2-2.8) for 1 to 2 drinks per week to 3.5 (95% CI 2.0-6.1) for more than 17 drinks per week, in comparison with less than 1 drink per week. Confounding by known or suspected determinants of breast cancer, smoking, use of oral contraceptives, lipid and vitamin consumption was looked into. Significant interactions were found with level of education and lipid consumption, with a higher risk for alcohol in women having had less schooling or consuming less fat. Adjustment with respect to the other risk factors did not modify the relationship. There was a significant risk increase both for wine and stronger drinks. Along with several other studies, our results give support to the hypothesis that alcohol is a risk factor in breast carcinogenesis.

Alcohol, cigarette smoking and breast cancer

The results of two case-control studies of breast cancer which included questions on exposure to tobacco and alcohol are reported. One study included 998 hospital cases and a like number of matched hospital controls while the other included 118 cases identified during mammographic screening and a like number of matched normal screenees. Both studies used the same questionnaires and the same methods to obtain information. The results with regard to cigarette smoking differed between the two studies. The hospital-based study showed a decreased risk of breast cancer with increasing amounts smoked (relative risk for 15 or more cigarettes per day was 0.82, 95% confidence interval 0.60-1.13) while the screening study showed an increased risk (relative risk for 15 or more cigarettes per day was 2.90, 95% confidence interval 1.16-7.25). Evidence is presented that both results may be attributable to bias in the selection of cases and controls. It is concluded that reliable results on the relationship between smoking and breast cancer are only likely to come from population-based studies. These studies, in general, have found no relationship. Neither study produced any hint of an association between alcohol consumption and breast cancer. From this, it appears that bias in subject selection may not be such a significant factor in interpretation of studies of alcohol and breast cancer as it is in studies of smoking and the disease. A number of other difficulties in the interpretation of studies of alcohol and breast cancer are considered, including the great variation in the amount of alcohol consumed. It is concluded that the assertion that alcohol is a risk factor for breast cancer remains unproven.

Alcohol and breast cancer: an overview

We have reviewed available reports from 1974-1987 linking alcohol consumption with breast cancer. Although three prospective studies show a slightly increased risk of breast cancer for consumers versus non-consumers of alcohol, the results of correlation studies and case control studies have been inconsistent. In both positive and negative studies the amount of alcohol consumed by women with breast cancer was low, and if there is an association between alcohol and breast cancer, then it would appear that complete abstinence would be required to reduce the risk of this disease. At present, it seems premature to consider such a drastic recommendation until further information becomes available.

Cigarette smoking, alcohol consumption and risk of breast cancer in young women

The possible association between cigarette smoking, alcohol consumption and the risk of development of breast cancer before the age of 45 was investigated by means of a population-based case-control study in Sweden and Norway. Information was obtained, by personal interview, from 422 (89.2%) of all eligible patients with breast cancer newly diagnosed between May 1984 and May 1985, and from 527 (80.6%) of all age-matched controls. The possible confounding effects of oral contraceptive (OC) use, education, and reproductive and several other factors were taken into account in multivariate analyses. No association was found between ever smoking (versus never smoking) and breast cancer (odds ratio 1.0; 95% confidence interval (CI) 0.8-1.3). Further, there was no relation between breast cancer and duration of smoking, age at start of regular smoking, length of time since the start of regular smoking, or number of cigarettes smoked per day. There was no significant interaction between smoking, use of OCs, parity, and breast cancer. A moderate or high current consumption of beer, wine, liquor or total alcohol did not increase the risk of breast cancer. An alcohol intake of 5 grams per day or more was associated with a decreased risk of breast cancer (odds ratio 0.6; 95% CI 0.4-0.9), but possible effects of a change in habits after diagnosis, of recall bias and of residual confounding, e.g. by dietary habits, need serious consideration.

Alcohol and breast cancer: a cohort study

The relation between alcohol consumption and several causes of death, including breast cancer, was examined in a population of 581, 321 women enrolled in a prospective study in 1959 and followed for 12 years. Women who drank occasionally had about the same breast cancer mortality rate as nondrinkers; those who drank one to four drinks per day had SMRs 7-26% higher; five drinks per day, 1.89; and six or more drinks per day, 1.65. The two highest-consumption groups' risks were significantly higher than those of nondrinkers after multivariate adjustment for several breast cancer risk factors. Distinctive dose-response relationships were observed for two known alcohol-related conditions: cirrhosis of the liver and cancer of the aero-digestive tract, suggesting that results for other causes are not seriously biased by misclassification of drinking habits. Death rates from all causes combined were elevated for drinkers of three or more drinks per day. Whether or not the association of elevated breast cancer death rates ultimately turns out to be causal, there is ample reason to continue to warn the public against excessive drinking.

Diet and cancer. Any progress in the interim?

It has been 5 years since the National Research Council (NRC) Committee on Diet, Nutrition and Cancer published "Interim Dietary Guidelines" for the nutritional prevention of cancer. The term "interim" implies that these recommendations should be regarded as temporary, pending more definitive findings from additional scientific research. This article reviews findings relevant to the connections between diet and cancer that have emerged from nutritional epidemiology subsequent to the 1982 the NRC report. Some recent research has supported the earlier work which served as a basis for the interim recommendations, some has not, and additional hypotheses have emerged. There continues to be evidence, although it is inconsistent, that dietary fat may be an important factor in colon cancer, and that something related to fruits and vegetables, perhaps carotene, may lower the risk of lung cancer. However, the hypothesized relationships between dietary fat and breast cancer and between dietary fiber and colon cancer have been less consistently supported by new findings. Meanwhile, a new hypothesis has emerged relating alcohol intake to breast cancer risk, although many important questions remain regarding the age at which alcohol use may affect risk, and the dose above which risk is increased. The last 5 years seem to have been characterized by only slow progress in our understanding of the relationship between diet and cancer. It is clear that in 1988 we are still very much in the interim. Critical methodologic assessments of the reasons for the discrepancies in findings among the various studies, and meta analytic approaches may be helpful in increasing our understanding of the set of epidemiologic research conducted to date. More important, however, are the many types of studies now underway, including more rigorously designed observational studies and chemo-preventive and dietary-preventive trials. These studies will likely provide more definitive future answers to the questions we still face in the interim.

Alcohol consumption and risk of breast cancer

In a population-based case-control study conducted in Adelaide, South Australia, and involving 451 case-control pairs aged 20-74 years, the risk of breast cancer for women consuming more than 9.3 g of alcohol per day was 50% higher than for non-drinkers (unadjusted RR 1.46, 95% CI 1.00-2.13). The increase in risk persisted upon control for potential confounding variables including dietary or diet-related factors, and was not restricted to any particular type of beverage. Lower levels of alcohol consumption were not associated with substantial alterations in risk of breast cancer. When examined within menopausal strata, the effect of alcohol was more pronounced in pre-menopausal women, although none of the estimates of effect within menopausal strata were statistically significant. Although positive associations between alcohol consumption and risk of breast cancer have been observed in previous studies, support for a causal association is, at most, qualified. However, given the widespread nature of this exposure, at least in developed countries, further and more detailed investigations of this association are required.

Alcohol consumption and breast cancer in the epidemiologic follow-up study of the first National Health and Nutrition Examination Survey

We investigated the relation between alcohol consumption and breast cancer in the Epidemiologic Follow-up Study of the first National Health and Nutrition Examination Survey, a cohort study based on sample of the U.S. population. A total of 7188 women 25 to 74 years of age who were examined during the period 1971 through 1975 were included in the analysis. Information about alcohol consumption was obtained during the base-line interview. The median follow-up period for this cohort was 10 years. One hundred twenty-one cases of breast cancer that developed after the baseline examination were identified through hospital records or death certificates. The relative-risk estimate for any amount of drinking relative to no drinking was 1.5 (95 percent confidence interval, 1.1 to 2.2). The estimates for three levels of consumption, from the lowest to the highest, were 1.4 (confidence interval, 0.9 to 2.3), 1.5 (0.9 to 2.6), and 1.6 (1.0 to 2.7), in comparison to no drinking at all. These relative-risk estimates were not materially affected by adjustment for known risk factors for breast cancer or for several dietary factors. The results of this study, consistent with those of two other cohort studies and a number of case-control studies, suggest that moderate alcohol consumption is associated with an elevation in the risk of breast cancer of 50 to 100 percent.

Moderate alcohol consumption and the risk of breast cancer

In 1980, 89,538 U.S. women 34 to 59 years of age, with no history of cancer, completed an independently validated dietary questionnaire that included the use of beer, wine, and liquor. During the ensuring four years, 601 cases of breast cancer were diagnosed among cohort members. Among the women consuming 5 to 14 g of alcohol daily (about three to nine drinks per week), the age-adjusted relative risk of breast cancer was 1.3 (95 percent confidence limits, 1.1 and 1.7). Consumption of 15 g of alcohol or more per day was associated with a relative risk of 1.6 (95 percent confidence limits, 1.3 and 2.0; Mantel extension chi for linear trend = +4.2; P less than 0.0001). Adjustment for known breast cancer risk factors and a variety of nutritional variables did not materially alter this relation. Significant associations were observed for beer and liquor when considered separately. Among women without risk factors for breast cancer who were under 55 years of age, the relative risk associated with consumption of 15 g of alcohol or more per day was 2.5 (95 percent confidence limits, 1.5 and 4.2). These prospective data derived from measurements of alcohol intake recorded before the diagnosis of breast cancer confirm the findings of several previous case-control studies. Viewed collectively, they suggest that alcohol intake may contribute to the risk of breast cancer.

Dietary factors and the risk of breast cancer

We evaluated the risk of breast cancer in relation to the frequency of consumption of a few selected dietary items. Data were used from a case-control study of 1,108 histologically confirmed breast cancer patients and 1,281 control subjects who were in the hospital for acute conditions unrelated to any of the established or suspected risk factors for breast cancer. Moderately elevated risk estimates were associated with higher levels of fat consumption in seasonings [butter, margarine, and oil, relative risk (RR) = 1.34, 95% confidence interval (CI) = 1.06-1.71] and meat (RR = 1.36, 95% CI = 1.12-1.65), whereas a reduced risk (RR = 0.42, 95% CI = 0.34-0.51) was associated with a more frequent green vegetable consumption. It was not possible to show that these associations were incidental, because allowance for several identified potential confounding factors, including the major identified or potential risk factors for breast cancer, did not materially modify the risk estimates. Further, no appreciable interaction emerged with age or menopausal status, because the diet-related risk estimates were similar in pre- or postmenopausal women. However, the implications of these findings in terms of specific micronutrients (e.g., retinol or beta-carotene) and biological correlates are still unclear. Alcohol consumption was significantly greater among breast cancer cases, with a multivariate risk estimate of 2.92 for the highest level. Thus, the present findings confirm that various aspects of diet may influence the risk of breast cancer, although the small amount of available knowledge does introduce serious uncertainties in any discussion of the potential implications in terms of prevention on a public health scale.

Alcohol and cancer

The cancers consistently associated with ingestion of alcohol, the head and neck cancers, are also associated with tobacco use and arise from epithelia that are in direct contact with both agents. Tobacco smoking-related cancers at sites not directly in contact with alcoholic beverages, that is, lung, bladder, and perhaps pancreas, do not consistently show a relationship to alcohol consumption, although lung and pancreatic tumors are associated in some studies. Liver cancer was thought to be strongly related to alcohol consumption on epidemiological grounds and because of its relationship to cirrhosis. As knowledge of the viral etiology of some cirrhoses has evolved and as methods to detect viruses have developed, the significant association between hepatitis B virus and hepatocellular carcinoma has become clear. Alcohol and hepatitis B virus may interact in the etiology of the disease and have important separate roles as well. There are epidemiologic and experimental data showing that malnutrition (resulting from poor food choice), economic deprivation, or alcoholism contributes to the risk for head, neck, and liver cancers. Colon cancers occur about equally in men and women, are found in well-nourished populations, and are not associated with tobacco smoking. Rectal cancers show a preponderance of cases in men but are frequently found in women as well and are not thought to be associated with smoking or malnutrition. The association between colorectal cancers and alcohol consumption, when it is found, apparently occurs at even relatively low alcohol intakes and is often stronger for consumption of beer than of other beverages. Nutritional and metabolic mechanisms proposed for the influence of alcohol on carcinogenesis are supported by studies in human subjects and laboratory animals. Animal models are needed in which effects of ethanol on carcinogenesis can be consistently demonstrated and which can then be used to examine mechanisms.