Risk factors for breast cancer by oestrogen receptor status: a population-based case-control study

Fish Intake Is Positively Associated with Breast Cancer Incidence Rate

Animal studies have, in general, been supportive of a protective effect of fish and fish (n-3) PUFA against breast cancer risk; but the epidemiologic evidence of such a relationship is limited. Case-control and cohort studies have rarely shown significant associations. The association between total fish intake and the effect of fat content and preparation method of the fish, in relation to the incidence rate ratios of breast cancer, were investigated among postmenopausal women. We also investigated the effect of fish intake with respect to estrogen receptor expression of breast cancer tumors. A total of 23,693 postmenopausal women from the prospective study "Diet, Cancer and Health" were included in the study. During follow-up, 424 women were diagnosed with breast cancer. The incidence rate ratio (IRR) and 95% CI per each additional 25 g of mean daily intake of fish were 1.13 (CI, 1.03-1.23). Analysis of fatty fish gave IRR of 1.11 (CI, 0.91-1.34), and the result for lean fish was 1.13 (CI, 0.99-1.29). When fish intake was stratified into three types of preparation methods, the IRR for fried fish was 1.09 (CI, 0.95-1.25), for boiled fish 1.09 (CI, 0.85-1.42), and for processed fish 1.12 (CI, 0.93-1.34). The IRR per additional 25 g of mean daily intake of fish was 1.14 (CI, 1.03-1.26) for estrogen receptor-positive (ER+) and 1.00 (CI, 0.81-1.24) for estrogen receptor-negative (ER-) breast cancer. In conclusion, this study showed that higher intakes of fish were significantly associated with higher incidence rates of breast cancer. The association was present only for development of ER+ breast cancer.

Fruits and vegetables intake differentially affects estrogen receptor negative and positive breast cancer incidence rates

Despite intensive research, the evidence for a protective effect of fruits and vegetables on breast cancer risk remains inconclusive. Other risk factors for breast cancer seem to vary with the estrogen receptor status of the breast tumor, and it is thus possible that the inconsistent results regarding a preventive effect of fruits and vegetables are due to lack of controlling for estrogen receptor status. The objective of this study was to investigate the effect of fruit and vegetable intake on postmenopausal breast cancer and explore whether the estrogen receptor status of the tumor modifies this relation. Postmenopausal women (n = 23,798; aged 50-64 y) provided information about diet and established risk factors for breast cancer in the cohort "Diet, Cancer and Health." During follow-up, 425 cases were diagnosed with breast cancer. Associations between intake of fruits and vegetables and the breast cancer rate were analyzed using Cox's regression model. The association for all breast cancers was an incidence rate ratio (IRR) of 1.02 (95% CI, 0.98-1.06) per 100 g/d increment of total intake of fruits, vegetables and juice. For estrogen receptor-positive (ER(+)) breast cancer, a borderline significant increase in the rate was seen, IRR: 1.05 (95% CI, 1.00-1.10), whereas a preventive effect was seen for estrogen receptor-negative (ER(-)) breast cancers, IRR: 0.90 (95% CI, 0.81-0.99). In conclusion, we did not find the overall breast cancer rate to be associated with the intake of fruits and vegetables, but there seemed to be different effects for ER(+) and ER(-) breast cancer.

Dietary intake of selected fatty acids, cholesterol and carotenoids and estrogen receptor status in premenopausal breast cancer patients

Although a wealth of research has focused on the influence of diet on breast cancer risk, the relationships between dietary factors and tumor characteristics of breast cancer, like estrogen receptor (ER) status, are not well characterized. In a case-case study, we evaluated self-reported dietary intake for five individual carotenoids, selected fatty acids, and cholesterol 1 year before diagnosis in 34 premenopausal breast cancer patients with ER-negative tumors and 86 premenopausal breast cancer patients with ER-positive tumors from The University of Texas M. D. Anderson Cancer Center. In multivariate logistic regression analysis adjusted for age, body mass index, and ethnicity, high intakes of linoleic acid were associated with more than a threefold greater risk of ER-negative disease than ER-positive disease (odds ratio (OR) = 3.48, 95% confidence interval (CI) = 1.42-8.54), whereas high cholesterol intake was associated with lower risk of ER-negative disease (OR = 0.35, 95% CI = 0.14-0.92). In a model evaluating carotenoids, selected fatty acids, and cholesterol together, the association with high intake of linoleic acid remained statistically significant (OR = 3.96,95% CI = 1.53-10.25), while those for high intake of cholesterol (OR = 0.38, 95% CI = 0.14-1.03) and low intake of cryptoxanthin (OR = 0.43, 95% CI = 0.17-1.06) were of marginal significance. While no striking associations were observed for the intakes of total carotenoids, selected fatty acids, and cholesterol, our analysis revealed an association for the consumption of a specific fatty acid (i.e., linoleic acid), suggesting dietary influence of this factor on ER status in premenopausal breast cancer patients. However, larger studies are needed to clarify the role of micronutrients in ER status in breast cancer.

Smoking (active and passive) and breast cancer: epidemiologic evidence up to June 2001

The first generation of studies evaluating the association between exposure to tobacco smoke and breast cancer merely compared active to nonactive smokers, with varying degrees of detail in the definition of active smoking. With rare exceptions, studies of this kind failed to show an effect of smoking on breast cancer risk. However, such analysis is probably insufficient. The most recent reports on the smoking-breast cancer connection have two characteristics. Some have separated women exposed to passive smoking from those nonexposed to either active or passive smoke. Other reports have focused on factors that modify the effect of smoking on breast cancer incidence, such as genetic markers or hormone receptors. A minority of reports combines these two characteristics. This review addresses the epidemiologic evidence for a link between smoking and breast cancer and discusses the implications of this evidence for future studies.

Organochlorine exposures influence on breast cancer risk and survival according to estrogen receptor status: a Danish cohort-nested case-control study

BACKGROUND

The relationship between breast cancer and organochlorine exposure is controversial and complex. As estrogen receptor positive and negative breast cancer may represent different entities of the disease, this study was undertaken to evaluate organochlorines influence on breast cancer risk and survival according to receptor status.

METHODS

The background material stems from the Copenhagen City Heart Study (Denmark 1976-78). The breast cancer risk was investigated in a cohort nested case-control design including 161 cases and twice as many breast cancer free controls. The cases served as a cohort in the survival analysis. Serum organochlorine concentrations were determined by gaschromotography.

RESULTS

The observed increased breast cancer risk associated with exposure to dieldrin derived from women who developed an estrogen receptor negative (ERN) tumor (Odds ratio [OR] I vs. IV quartile, 7.6, 95% confidence interval [95% CI] 1.4-46.1, p-value for linear trend 0.01). Tumors in women with the highest dieldrin serum level were larger and more often spread at the time of diagnosis than ERP tumors. The risk of dying was for the remaining evaluated compounds higher among patients with ERP breast cancer when compared to those with ERN. In the highest quartile of polychlorinated biphenyls (SigmaPCB) it was more than 2-fold increased (Relative risk [RR] I vs. IV quartile, 2.5, 95% CI 1.1-5.7), but no dose-response relation was apparent.

CONCLUSION

The results do not suggest that exposure to potential estrogenic organochlorines leads to development of an ERP breast cancer. A possible adverse effect on prognosis of hormone-responsive breast cancers needs to be clarified.

Effect of ethanol on proliferation and estrogen receptor-alpha expression in human breast cancer cells

There is substantial epidemiological evidence suggesting that alcohol consumption is associated with increased risk for breast cancer. However, possible biological mechanisms have not been clearly established. In the present studies, a direct effect of ethanol on the proliferation and intracellular content of cyclic AMP (cAMP) in two estrogen receptor-positive (ER+) and two estrogen receptor-negative (ER-) human breast cancer cell lines was examined. Treatment of ER+ human breast cancer cells (MCF-7 and ZR75.1) with ethanol at concentrations between 10 and 100 mM was associated with increased cell numbers compared to controls. The ERalpha content and the amount of intracellular cAMP also increased in ER+ cells exposed to ethanol, compared to controls. On the other hand, ethanol treatment did not increase cell proliferation or cAMP levels in the ER- (BT-20 and MDA-MB-231) human breast cancer cells. Therefore, ethanol added at physiologically relevant concentrations to ER+ human breast cancer cell cultures can enhance cell proliferation and increase the content of ERalpha.

Smoking associated with hormone receptor negative breast cancer

Women who smoke have less favourable prognosis following breast-cancer diagnosis. Some studies suggest that this is due to a more advanced stage at diagnosis, on average. Our present aim was to assess whether smoking is associated with other prognostic markers as well, e.g., hormone receptor status, histopathology and tumour differentiation. The evaluation was based on 268 incident cases in a cohort of 10,902 women (35% smokers) followed for an average of 12.4 years. An immunohistochemical method on recuts of tumour tissue was used to assess hormone receptor status. One pathologist classified all tumours according to the WHO system, Nottingham grade and Nottingham Prognostic Index. The relative risk (RR) of oestrogen receptor-negative tumours was, for current smokers, 2.21 [95% confidence interval (CI) 1.23-3.96] and, for ex-smokers, 2.67 (95% CI 1.41-5.06) compared to never-smokers. Ex-smokers had an increased risk of progesterone receptor-negative tumours (RR = 1.61, 95% CI 1.07-2.41), but there were no other significant associations between smoking habits and oestrogen receptor-positive or progesterone receptor-positive or -negative tumours. The incidence of Nottingham grade III tumours was higher in ex-smokers than in never-smokers (RR = 2.03, 95% CI 1.17-3.54). In terms of histopathological type or Nottingham Prognostic Index, there were no significant differences between smoking groups. We conclude that smoking is associated with an increased occurrence of hormone receptor-negative tumours.

Tumor variants by hormone receptor expression in white patients with node-negative breast cancer from the surveillance, epidemiology, and end results database

PURPOSE

Hormone receptor expression (presence-positive or absence-negative) may reflect different stages of one disease or different breast cancer types. Determining whether hormone receptor expression represents one or more breast cancer phenotypes would have important paradigmatic and practical implications.

METHODS

Breast cancer records were obtained from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) database. The study included 19,541 non-Hispanic white women with node-negative breast cancer. Standard tumor cell characteristics and breast cancer-specific survival were analyzed by independent estrogen receptor (ER+ and ER-), independent progesterone receptor (PR+ and PR-), and joint ERPR expression (ER+PR+, ER+PR-, ER-PR+, and ER-PR-).

RESULTS

Age frequency density plots by hormone receptor expression showed two overlapping breast cancer populations with early-onset and/or late-onset etiologies. Independent ER+ and PR+ phenotype were associated with smaller tumor sizes, better grade, and better cancer-specific survival than ER- and PR- breast cancer types. Joint ERPR phenotype exhibited biologic gradients for tumor size, grade, and cancer-specific survival, which ranked from good to worse for ER+PR+ to ER+PR- to ER-PR+ to ER-PR-.

CONCLUSION

Variations of standard tumor cell characteristics and breast cancer-specific survival by hormone receptor expression in white patients with node-negative breast cancer suggested two breast cancer phenotypes with overlapping etiologies and distinct clinical features.

Breast cancer incidence in relation to smoking cessation

High plasma levels of oestrogens are associated with increased breast cancer risk. If smoking, as has been suggested, have both a tumour initiating mutagenic effect and a protective anti-oestrogenic effect, one would assume that smokers who give up smoking have the highest incidence of breast cancer. This was evaluated in the follow-up of a cohort of 10,902 women of whom 4,359 were premenopausal. Record-linkage with official cancer registries yielded 416 incident cases during an average follow-up of 13.6 years. The adjusted relative risk in all ex-smokers was 1.31 (1.02-1.69), as compared to never smokers, and in premenopausal ex-smokers it was 1.57 (1.07-2.30). Breast cancer incidence in premenopausal ex-smokers was inversely related to time since cessation, (p for trend = 0.01), and was highest among the women who had given-up smoking less than 12 months before screening: 2.76 (1.55-4.91). There was no significant association between current smoking and breast cancer risk. We conclude that incidence of breast cancer in premenopausal women who have given up smoking is higher than it is in smokers and never smokers. To what extent this may be related to endocrine effects associated with smoking cessation remains to be evaluated.

Meta-analysis of studies on breast cancer risk and diet: the role of fruit and vegetable consumption and the intake of associated micronutrients

A meta-analysis was carried out, in order to summarise published data on the relationship between breast cancer, fruit and vegetable consumption and/or the intake of beta-carotene and vitamin C. Relative risks were extracted from 26 published studies from 1982 to 1997. Random and fixed effects models were used. Between studies, heterogeneity was found for vegetables, fruit, vitamin C but not for beta-carotene. Summary relative risk (RR) estimates based upon a random effects model, except for beta-carotene, for 'high consumption' compared with 'low consumption', derived from the studies satisfying the inclusion criteria were as follows: vegetable consumption: RR=0.75 (95% CI (confidence interval) 0.66-0.85) from 17 studies; fruit consumption: RR=0.94 (95% CI 0.79-1.11) from 12 studies; vitamin C: RR=0.80 (95% CI 0.68-0.95) from 9 studies; beta-carotene: RR=0.82 (95% CI 0.76-0.91) from 11 studies. This analysis confirms the association between intake of vegetables and, to a lesser extent, fruits and breast cancer risk from published sources. Increasing vegetable consumption might reduce the risk of breast cancer.

Familial aggregation of breast cancer with early onset lung cancer

Site-specific familial aggregation and evidence supporting Mendelian codominant inheritance have been shown in lung cancer. In characterizing lung cancer families, a number of other cancers have been observed. The current study evaluates whether first-degree relatives of early onset lung cancer cases are at increased risk of breast cancer. Families were identified through population-based lung cancer cases and controls under 40 years of age. Cases were ascertained through the Metropolitan Detroit SEER registry; controls through random-digit dialing. Data were available for 384 female relatives of 118 cases and 465 female relatives of 161 controls. Breast cancer in relatives was evaluated after adjusting for age, race, sex, and smoking status of each family member and the sex and age of the probands. A positive family history of early onset lung cancer increased breast cancer risk among first-degree relatives 5. 1-fold (95% CI, 1.7-15.1). Relatives of cases with adenocarcinoma of the lung were at highest risk (RR = 6.3, 95% CI 2.0-20). Mean age of breast cancer diagnosis among relatives of cases was 52.2 years and not statistically different from relatives of controls. Three case families also reported early ovarian cancers (mean age of diagnosis of 35 years). These findings suggest that shared susceptibility genes may act to increase risk of early onset lung and breast cancer in families.

Estrogen and progesterone receptor concentrations and prevalence of tumor hormonal phenotypes in older breast cancer patients

We examined the concentrations of estrogen (ER) and progesterone receptors (PR) and the distribution of tumor phenotypes as a function of age in breast cancer patients. ER and PR concentrations were determined in tissue biopsies from 1739 patients with primary breast cancer, using ligand binding assays. Tumors were classified as estrogen receptor positive (ER+) or negative (ER-) and progesterone receptor positive (PR+) or negative (PR-) based on the presence or absence of receptor binding activity. Tumors were stratified into four phenotypes: ER+PR+; ER+PR-; ER-PR+; and ER-PR-. Significant positive associations were found between ER concentration and age (p = 0.0001) and between PR concentration and age (p = 0.0002). The median ER concentrations were statistically different by age groups, with the greatest levels in older versus younger patients. The prevalence of ER+PR+ tumor phenotype increased with age. In contrast, the prevalence of ER-PR- and ER-PR+ tumor phenotypes decreased with age. The median PR-to-ER ratio decreased with age (p = 0.0001), and this trend was attributed to increased ER concentration with age. The prevalence of ER-PR- and ER-PR+ tumor phenotypes is greater in younger patients suggesting that hormonal regulation of ER gene expression may be responsible for the observed age disparity of tumor phenotypes in breast cancer.

Alcohol consumption and breast cancer oestrogen and progesterone receptor status

We examined the role of alcohol on the risk of breast cancer by the joint oestrogen receptor (ER) and progesterone receptor (PR) status of the tumour using data from two case-control studies conducted in Los Angeles County, USA. Eligible premenopausal patients were 733 women aged < or =40 years and first diagnosed from 1 July 1983 to 1 January 1989. Eligible postmenopausal patients were 1169 women aged 55-64 years and first diagnosed from 1 March 1987 to 31 December 89. Patients were identified by the University of Southern California Cancer Surveillance Program. Neighbourhood controls were individually matched to patients by parity (premenopausal patients) and birth date (+/-3 years). ER and PR status were obtained from medical records for 424 premenopausal and 760 postmenopausal patients. The analyses included 714 premenopausal and 1091 postmenopausal control subjects. Alcohol use was generally not associated with premenopausal risk of breast cancer, regardless of hormone-receptor status. Among the postmenopausal women, those who consumed, on average, > or =27 g of alcohol/d experienced an odds ratio (OR) of 1.76 [95% confidence interval (CI) 1.14-2.71] for ER-positive/PR-positive breast cancer relative to women who reported no alcohol consumption. Alcohol use was less clearly associated with risk of other receptor types among postmenopausal women. These data suggest that alcohol may preferentially increase risk of ER-positive/PR-positive breast cancer in postmenopausal women.

Relation of smoking to breast cancer by estrogen receptor status

It has been suggested that smoking is associated with estrogen-negative breast cancer but not with estrogen-positive breast cancer. A population-based case-control study was conducted in Geneva, Switzerland, to determine the relation of passive and active smoking to breast cancer when the referent unexposed category consisted of women unexposed to active and passive smoke. The 242 patients with breast cancer (cases), in whom estrogen receptor (ER) status was determined on biopsy material, were compared with 1,059 women free of breast cancer (controls). Lifetime history of active and passive smoking was recorded year by year, between age 10 and the date of interview. Prevalence rates of ER+ tumors were 74.7% in pre-menopausal women and 74.2% in post-menopausal women. Post-menopausal active smokers had a lower prevalence of ER+ tumors (70.0%, p = ns). Among pre-menopausal women, the age-adjusted ORs of breast cancer with having smoked an average of > or = 20 cigarettes per day (cpd) during lifetime were 2.7 for ER- tumors and 2.6 for ER+ tumors. Among post-menopausal women, corresponding ORs were 5.7 for ER- tumors and 2.4 for ER+ tumors. Smoking was related to both ER- and ER+ breast cancer in pre- and post-menopausal women, but the strength of the association appeared to be greater for ER- tumors among post-menopausal women.

Estrogen receptor status of breast cancer: a marker of different stages of tumor or different entities of the disease?

Breast cancer can be divided into two types according to the estrogen receptor (ER) level of the tumor: ER-positive and ER-negative. Two hypotheses have been raised about the relationship between ER-positive and ER-negative breast tumors. One hypothesis considers ER status as an indicator of a different stage of the disease. The other regards ER-positive and ER-negative tumors as different entities. For both etiological and biological studies of breast cancer it is important to know which hypothesis is correct. In this paper, we review evidence for and against each hypothesis and suggest issues to be addressed in future studies.

Tumor characteristics and survival of breast cancer patients in relation to premorbid diet and body size

Nutritional factors have been suggested to play an important role in the prognosis of breast cancer through their effect on tumor characteristics. This study evaluated four tumor characteristics and prognosis in relation to premorbid diet and body size. From a cohort of 89,835 women in the National Breast Screening Study (NBSS) in Canada, data on 676 incident cases of invasive carcinoma of breast, on whom we had dietary information, were used. A high energy intake lowered the likelihood of being ER positive and PR positive but after adjusting for ER status, was still associated with a higher risk of dying of breast cancer. Total fat and various types of fats were associated with a greater likelihood that a woman would be ER and PR positive, however the likelihood of dying from breast cancer was higher with higher fat consumption. There was no significant effect of higher intakes of beta carotene or vitamin C on ER status, nodal status or tumor size, but a significantly lower risk of dying from breast cancer was observed. Higher intake of carbohydrates and calcium was associated with a lowered frequency of ER and PR positive status but also with a lower risk of dying. Of the five indicators of body size studied, higher triceps skinfold thickness was associated with a slightly lower chance of being ER positive, PR positive, and node negative, and a significantly higher likelihood of dying. It appears that while there are significant associations between some of the diet and body size variables and tumor characteristics, the effect of most nutritional factors on prognosis in breast cancer may not be mediated via their effect on tumor characteristics.

Hormones and breast and endometrial cancers: preventive strategies and future research

A number of hormonal approaches for prevention of endometrial and breast cancers have been proposed. Because of the hormonal responsiveness of both tumors, much attention has focused on effects of exogenous hormone use. Although estrogens in hormone replacement therapy increase the risk of endometrial cancer, the disease is substantially reduced by long-term use of oral contraceptives. The issues with breast cancer are more complex, mainly because of a variety of unresolved effects. Long-term estrogen use is associated with some increase in breast cancer risk, and certain patterns of oral contraceptives appear to predispose to early-onset disease. With respect to estrogens, preventive approaches for both tumors would include use for as limited periods of time as possible. Addition of a progestin appears to lower estrogen-associated endometrial disease, but its effect on breast cancer risk remains less clear. Additional studies on effects of detailed usage parameters should provide useful insights into etiologic mechanisms. Other preventive approaches for endometrial cancer that may work through hormonal mechanisms include staying thin, being physically active, and maintaining a vegetarian diet. Breast cancer risk may possibly be reduced by extended periods of breastfeeding, restriction of intake of alcoholic beverages, remaining thin later in life, and being physically active. Additional research is needed to clarify the biologic mechanisms of these associations. The bridging of epidemiology with the biologic sciences should clarify many unresolved issues and lead to better preventive approaches.

Parity is associated with axillary nodal involvement in operable breast cancer

INTRODUCTION

Although multiparous women have a decreased incidence of breast cancer, several series have observed that multiparous women have a higher risk of axillary nodal metastases and diminished survival.

METHODS

To study this hypothesis in greater detail, this study analyzed data from 223 consecutive women with clinically operable (T1-3, N0-1, M0) breast cancer, all of whom had undergone axillary node dissection (AND) by one surgeon (83 mastectomy/AND, 140 lumpectomy/AND). The number of pregnancies and other hormonally related factors were recorded. Results were compared to pathologic data (node status, tumor size, estrogen and progesterone receptors).

RESULTS

Seventy-eight patients (35.0%) had positive axillary nodes. Increasing parity was associated with an increased likelihood of positive nodes (Odds ratio 1.22 (95% CI: 1.04-1.42), p = 0.012) as was increasing tumor size (Odds ratio 1.31 (1.07-1.59), p = 0.007). The effect of parity was independent of tumor size, age, or hormone receptors.

CONCLUSIONS

In this series, which includes only operatively staged patients, increasing parity is associated with nodal positivity. This effect is of a magnitude similar to that of increasing tumor size, and confirms observations from other studies. Information regarding parity may be useful for prognostic purposes, as well as providing insights into basic breast cancer biology.

An examination of obesity and breast cancer survival in post-menopausal women

A historical prospective study was conducted at the Mercy Hospital of Pittsburgh, Pennsylvania (USA), to study the role of post-menopausal obesity in the recurrence and survival of breast cancer. Records from 301 post-menopausal women diagnosed with breast cancer from 1977 to 1985 were followed for at least 5 years from data supplied by the Tumor Registry and medical records. Data collected included age, height, weight, race, hormone receptor status, stage and size of tumour, number of positive nodes, site of distant metastasis, first course of treatment, and 5 year recurrence and survival. Forty-five per cent of patients were obese (n = 136), while 55% were non-obese (n = 165). Obesity was defined by the Quetelet index (patients with values > 27 were considered obese). The recurrence rates for the obese and non-obese groups were 40% and 39% respectively, and were not significantly different. Univariate and multivariate analyses showed that there was no significant association between obesity in post-menopausal women and likelihood of recurrence of or death from breast cancer.

A hospital-based case-control study of breast-cancer risk factors by estrogen and progesterone receptor status

It has been proposed that breast cancers may differ in their pathogenesis and etiology according to their estrogen receptor (ER) and progesterone receptor (PR) status. This hospital-based case-control study in Japan assessed the relationship between known and suspected breast-cancer risk factors and ER and PR status. Information on risk factors was collected from histologically confirmed breast-cancer cases (n = 519) and from cancer-free controls (n = 9,506). Of 160 cases with known ER status, 58 percent were ER-positive; 38 percent of 157 cases with known PR status were PR-positive. No statistically significant differences were found between ER-positive cf ER-negative cases. However, statistically significant differences between PR-positive cf PR-negative cases were observed for number of full-term pregnancies (P = 0.01), menstrual regularity as a teenager (P = 0.024), and occupation as housewife (P = 0.036). Borderline differences were observed for age at menopause (P = 0.074), and age at menarche (P = 0.083). This study provides some evidence that etiologic distinctions may be greater between PR-positive and PR-negative breast cancers than between ER-positive and ER-negative breast cancers.

Breast cancer in Canada: to screen or not to screen?

Lomas (1988) and Sabatier (1987) have suggested models by which to examine the roles that values, scientific knowledge, institutions, and the learning process play in the formulation of both national and clinical health-care policies. Utilizing their frameworks, this article offers an explanation for the development of high-volume screening mammography policies in Canada, despite the suggested inefficacy of screening technologies for 'unavoidable' illnesses such as carcinoma in the breast. The preliminary results of Canada's National Breast Screening Study further complicate this tissue. Inappropriate framing of the 'problem' in the policy-making process, by actors highly influenced by societal values and scientific evidence, is identified as the reason for present and planned policies and practices contradicting the first principles of health-policy analysis.

Fruit, vegetables, and cancer prevention: a review of the epidemiological evidence

Approximately 200 studies that examined the relationship between fruit and vegetable intake and cancers of the lung, colon, breast, cervix, esophagus, oral cavity, stomach, bladder, pancreas, and ovary are reviewed. A statistically significant protective effect of fruit and vegetable consumption was found in 128 of 156 dietary studies in which results were expressed in terms of relative risk. For most cancer sites, persons with low fruit and vegetable intake (at least the lower one-fourth of the population) experience about twice the risk of cancer compared with those with high intake, even after control for potentially confounding factors. For lung cancer, significant protection was found in 24 of 25 studies after control for smoking in most instances. Fruits, in particular, were significantly protective in cancers of the esophagus, oral cavity, and larynx, for which 28 of 29 studies were significant. Strong evidence of a protective effect of fruit and vegetable consumption was seen in cancers of the pancreas and stomach (26 of 30 studies), as well as in colorectal and bladder cancers (23 of 38 studies). For cancers of the cervix, ovary, and endometrium, a significant protective effect was shown in 11 of 13 studies, and for breast cancer a protective effect was found to be strong and consistent in a meta analysis. It would appear that major public health benefits could be achieved by substantially increasing consumption of these foods.

Oral contraceptives and breast disease

Epidemiologic data support the hypothesis that the types of OCs used before the mid-1970s protected against most forms of benign breast disease. It is unclear whether current low-dose progestogen OCs will confer the same protection. Further studies are necessary to clarify this. For breast cancer, the relationship is more complex. It is possible that prolonged use of high-dose OCs exert a small increased risk for breast cancer development in women before age 45. Furthermore, prolonged use before a first term pregnancy may result in a small increase in risk for breast cancer before age 45. Studies evaluating the effect of current low-dose OCs are necessary to elucidate what, if any, effect they may have on breast cancer development. Furthermore, as our population ages, studies will be able to determine what effect, if any, may be present in women over age 60, those women with the highest underlying risk of breast cancer. And finally, more research of basic breast tissue physiology and the effect of endogenous and exogenous hormones on this complex organ is needed.

Steroid receptor status and the epidemiology of breast cancer

This case-control study examined risk factors for breast cancer according to tumor estrogen receptor (ER) status and progesterone receptor (PR) status. The data included 607 case patients and 1214 control subjects matched by age and residence. Of 528 case patients with steroid receptor information, 67% had ER-positive tumors and 55% had PR-positive tumors. Odds ratios for ER-positive and ER-negative breast cancer were similar with respect to menopausal status, age at menarche, history of cystic breast disease, and Quetelet Index. Family history of breast cancer was a stronger risk factor for ER-negative than for ER-positive breast cancer and the odds ratios for number of births were suggestive of a different effect. While ER and PR status were highly correlated, there were some differences in their associations with risk factors. Odds ratios for PR-positive and PR-negative breast cancer differed for number of births and were suggestive of differences with respect to menopausal status, Quetelet Index, and family history of breast cancer. These findings do not suggest different causal pathways for ER-positive and ER-negative breast cancer. However, they do indicate that PR status may play a role in the etiology of breast cancer.

Steroid receptors in breast cancer

Recent advances in steroid receptor structure and function now indicate that oestrogen binds to the oestrogen receptor (ER) molecule at a specific site, denoted region E. This allows binding of the oestrogen-ER complex to DNA via cysteine residues in region C of the ER molecule, which tetrahedrally co-ordinate zinc. This modulates transcription and stimulates cell growth. A number of newly discovered growth factors are also regulated by ER, as is the progesterone receptor. Steroid receptor concentrations in tissues can now be measured on smaller tissue samples using enzyme immunoassay or on cells obtained by fine needle aspiration using monoclonal antibody technology. The prognostic value of steroid receptor is limited, but still constitutes the best marker for predicting response to endocrine therapy. The role of steroid receptors in selecting patients for adjuvant therapy is discussed.