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Breast Health

November 2007

Energy balance and breast cancer risk: a prospective cohort study.

While there is evidence that breast cancer risk is positively associated with body mass index (in postmenopausal women) and energy intake and inversely associated with physical activity, few studies have examined breast cancer risk in association with energy balance, the balance between energy intake and expenditure. Therefore, in the cohort study reported here, we studied the independent and combined associations of vigorous physical activity, energy consumption, and body mass index (BMI), with breast cancer risk. The investigation was conducted in 49,613 Canadian women who were participants in the National Breast Screening Study (NBSS) and who completed self-administered lifestyle and food frequency questionnaires between 1980 and 1985. Linkages to national mortality and cancer databases yielded data on deaths and cancer incidence, with follow-up ending between 1998 and 2000. During a mean 16.4 years of follow-up, we observed 2,545 incident breast cancer cases. Due to exclusions for various reasons, the analyses were based on 40,318 subjects amongst whom there were 1,673 incident cases of breast cancer. Participation in vigorous physical activity and body mass index were not independently associated with breast cancer risk in the total cohort. A statistically significant positive trend was observed, however, between energy intake and breast cancer risk (P (trend )= 0.01). Although there was some variation in risk associated with vigorous physical activity, and BMI when the analyses were stratified by menopausal status, these interactions were not statistically significant. The interaction between menopausal status and energy intake, however, was of borderline statistical significance (P (interaction )= 0.06), with a statistically significant increased risk of breast cancer associated with highest versus lowest quartile of energy intake among premenopausal women (Hazard Ratio [HR] = 1.45, 95% confidence interval [CI] = 1.13- 1.85, P (trend) = 0.001). There was evidence of an increased risk of breast cancer associated with a relatively high body mass index among postmenopausal women in the highest quartile level of energy intake (Hazard Ratio [HR] = 1.72, 95% confidence interval [CI] = 1.01- 2.93, P (trend) = 0.05). In addition, there was evidence of an increased risk of breast cancer among premenopausal, physically inactive, overweight/obese women who consumed > or =1972 kcal/day compared to physically active normal weight women who consumed <1972 kcal/day (HR = 1.60, 95% CI = 1.08-2.37). Our data suggest that obese premenopausal women with relatively high energy intake may be at increased risk of breast cancer. In addition, energy imbalance, represented by a relatively high energy intake, lack of participation in vigorous physical activity, and a relatively high body mass index, may be associated with increased breast cancer risk, particularly among premenopausal women.

Breast Cancer Res Treat. 2006 May;97(1):97-106


Urinary estrogen metabolites and breast cancer: a case-control study.

Preliminary studies suggest that the estrogen metabolite 16 alpha-hydroxyestrone is associated with breast cancer, whereas 2-hydroxyestrone is not. However, epidemiological studies evaluating this relationship and taking established risk factors for breast cancer into account are lacking. The purpose of this study was to examine the association of the ratio of the urinary estrogen metabolites (2-hydroxyestrone and 16 alpha-hydroxyestrone) and of the individual metabolites with breast cancer. A spot urine sample, a brief history, and clinical data were collected from breast cancer cases (n = 42) and from women coming to the hospital for a routine mammogram or attending a free breast cancer screening (n = 64). 2-Hydroxyestrone and 16 alpha-hydroxyestrone were measured by enzyme immunoassay, and the estrogen metabolite ratio (EMR; 2-hydroxyestrone:16 alpha-hydroxyestrone) was computed. Cases and controls were similar in terms of age (mean age of cases, 53.8 +/- 15.1 years, versus 54.2 +/- 10.4 years for controls; P = 0.9) and demographics. Mean EMR was not associated with breast cancer overall (1.67 +/- 0.80 versus 1.72 +/- 0.66; P = 0.7). However, in postmenopausal women, the mean EMR was significantly lower in cases compared to controls (1.41 +/- 0.73 versus 1.81 +/- 0.71; P = 0.05). The multivariate adjusted odds ratios for the intermediate and lowest tertiles of the EMR relative to the highest among postmenopausal women were 9.73 (95% confidence interval, 1.27-74.84) and 32.74 (95% confidence interval, 3.36-319.09), respectively. The test for trend was highly significant (P = 0.003). Analyses of the individual metabolites indicated that 16 alpha-hydroxyestrone was a strong risk factor. The EMR did not show any consistent associations with age, race/ethnicity, age at first birth, parity, body mass index, family history of breast cancer, smoking, or alcohol intake. These data suggest a strong, inverse association of the EMR and a strong positive association of 16 alpha-hydroxyestrone with breast cancer in postmenopausal women. Larger studies are needed to confirm these results and to assess the relationship of the EMR and of the individual metabolites with breast cancer, with attention to menopausal status and clinical factors and with adjustment for known breast cancer risk factors.

Cancer Epidemiol Biomarkers Prev. 1997 Jul;6(7):505-9


Estrogen metabolism and breast cancer.

BACKGROUND: Specific pathways involved in estrogen metabolism may play a role in the etiology of breast cancer. We used data from a large population-based case-control study to assess the association of the urinary estrogen metabolites 2-hydroxyestrone (2-OHE1), 16alpha-hydroxyestrone (16-OHE1), and their ratio (2/16) with both invasive and in situ breast cancer. METHODS: Study participants from the Long Island Breast Cancer Study Project provided a spot urine specimen and completed a comprehensive interviewer-administered questionnaire. Women who used exogenous hormones or who took tamoxifen in the 6 months before urine collection were excluded from the analysis, leaving 269 invasive cases, 158 in situ cases, and 326 controls. Unconditional logistic regression was used to obtain adjusted odds ratios (ORs) for invasive and in situ breast cancer, separately, in relation to tertiles of the individual metabolites (standardized for creatinine) and the 2/16 ratio, stratified by menopausal status. RESULTS: The OR for invasive breast cancer was inversely associated with the 2/16 ratio among premenopausal women (OR = 0.50 for extreme tertiles; 95% confidence interval = 0.25-1.01). ORs ranged from 0.32 to 0.60 when women were stratified by whether cases had received chemotherapy within 6 months before urine collection and by estrogen receptor status. In postmenopausal women, there was a slight reduction in the odds ratio for invasive cancer with high levels of the 2/16 ratio (OR = 0.78; 95% confidence interval = 0.46-1.33). Neither the individual metabolites nor the ratio were associated with in situ breast cancer. CONCLUSION: These data provide support for the hypothesis that the 2/16 ratio is associated with reduced breast cancer risk. The most consistent associations were observed with invasive cancer in premenopausal women.

Epidemiology. 2006 Jan;17(1):80-8


Indole-3-carbinol. A novel approach to breast cancer prevention.

The results show that all of the carcinogens, oncogenes, and tumor-associated viruses that we have studied profoundly affect the extent of 2- and 16 alpha-hydroxylation in a prorisk direction. All of the dietary and biological responses associated with increased cancer risk decrease 2-hydroxylation and increase 16 alpha-hydroxylation. Remarkably, although PAHs are reported to induce P450-1A1, we have found them to decrease 2-hydroxylation. Finally, using indole-3-carbinol to induce 2-hydroxylation results in the chemoprevention of mammary tumors in rodents and recurrences of laryngeal papillomas in humans. Also correlating with these studies in HPV is the decrease in the C-2/C-16 alpha metabolite ratio observed in women with CIN relative to control subjects. The greatest decrease was observed in women with the most severe form, CIN3. These findings are under further investigation.

Ann NY Acad Sci. 1995 Sep 30;768:180-200


Hormonal profiles in women with breast cancer.

The literature findings on endogenous hormonal profiles in women with breast cancer are reviewed in detail. It is concluded that four sets of findings are valid: (1) diminished adrenal androgen production, probably genetic, in women with premenopausal breast cancer; (2) ovarian dysfunction (luteal inadequacy plus increased testosterone production) in breast cancer at all ages; (3) increased 16 alpha-hydroxylation of estradiol in breast cancer at all ages; and (4) evidence that prolactin is a permissive risk factor for breast cancer, and that the pregnancy-induced decrease in prolactin levels may account for the protective effect of early pregnancy against breast cancer.

Obstet Gynecol Clin North Am. 1994 Dec;21(4):751-72


Soy isoflavones—benefits and risks from nature’s selective estrogen receptor modulators (SERMs).

Phytoestrogens have become one of the more topical areas of interest in clinical nutrition. These non-nutrient bioactive compounds are ubiquitous to the plant kingdom and possess a wide range of biological properties that contribute to the many different health-related benefits reported for soy foods and flaxseeds--two of the most abundant dietary sources of phytoestrogens. Reviewed is the recent knowledge related to their pharmacokinetics and clinical effects, focusing mainly on isoflavones that are found in high concentrations in soy foods. Arguments are made for considering soy isoflavones as natural selective estrogen receptor modulators (SERMs) based upon recent data of their conformational binding to estrogen receptors. Rebuttal is made to several key and important issues related to the recent concerns about the safety of soy and its constituent isoflavones. This article is not intended to be a comprehensive review of the literature but merely highlight recent research with key historical perspectives.

J Am Coll Nutr. 2001 Oct;20(5 Suppl):354S-362S