Physical activity and breast cancer risk among women in the southwestern United States

The Clinicopathological Profile of Breast Cancer in Young Women from a Tertiary Care Center

Background Increasing number of young breast cancer patients are seen in India and many of these young breast cancer patients are considered to have more aggressive disease biology.

Aim The aim of this article was to study the clinicopathological profile of breast cancer patients in the young and older patients to understand the difference between these two groups.

Methods This was a retrospective study conducted on 421 breast cancer patients.

Results Total of 421 breast cancer patients were studied, out of which 158 patients were less than or equal to 40 years age group and 263 patients were in more than or equal to 50 years age group. Commonest T stage on presentation was T2, which was seen 56.32% of young breast cancer patients and in 64.64% of older patients. Higher nodal spread was seen in younger patients when compared with older patients (p-value = 0.00001). Older group patients had significant decline from anatomical to pathological prognostic stage group compared with younger group (29 vs. 13.29%; p-value = 0.00001). Grade 3 tumors were seen in 58.23% of younger patients and 22.05% of older patients (p-value = 0.00001). Triple-negative breast cancer was seen more commonly in younger group compared with older group (p-value = 0.0088).

Conclusions Significant number of breast cancer patients present in younger age group in India. Younger breast cancer patients tend to have higher grade tumors and triple-negative breast cancer is common in younger age groups. Pathological prognostic stage grouping appears clinically more relevant than anatomical stage groups.

Influence of physical activity at a young age and lifetime physical activity on the risks of 3 obesity-related cancers: systematic review and meta-analysis of observational studies

CONTEXT

Excess weight has been linked to increased risks of 13 types of cancers. Physical activity is a non-nutritional modifiable lifestyle factor that is not only crucial for weight control but is also known to regulate hormones and metabolic pathways that may contribute to carcinogenesis. There is solid evidence that being physically active during middle and late adulthood lowers the risks of 3 obesity-related cancers, namely breast cancer, colon cancer, and endometrial cancer. However, the associations between physical activity at a young age (childhood, adolescence, and young adulthood; age 5 to ≤30 yr) and lifetime physical activity and the risks of breast cancer, colon cancer, and endometrial cancer are less defined.

OBJECTIVE

The present systematic review and meta-analysis of observational studies was performed in accordance with the MOOSE guidelines to determine whether physical activity at a young age and lifetime physical activity may lower the risks of breast cancer, colon cancer, and endometrial cancer.

DATA SOURCES

The PubMed and Web of Science databases were searched for relevant observational studies published from inception to July 2018.

STUDY SELECTION

Observational studies (prospective cohort, case-cohort, nested case-control, historical cohort, and case-control) were considered relevant if they investigated the association between physical activity at a young age or lifetime physical activity and the risks of developing selected cancers.

DATA EXTRACTION

A random-effects meta-analysis was performed to generate the summary relative risk (RR) with 95%CI for the highest vs the lowest category of physical activity of any type.

RESULTS

Eighty publications were included in the present meta-analysis. Higher physical activity at a young age was associated with lower risks of breast cancer (RR 0.81, 95%CI 0.76, 0.87) and colon cancer (RR 0.67, 95%CI 0.50, 0.88). Similarly, lifetime physical activity was inversely associated with the risks of breast cancer (RR 0.79, 95%CI 0.72, 0.86) and colon cancer (RR 0.75, 95%CI 0.69, 0.82). For breast cancer, menopausal status did not appear to modify the observed inverse association. The benefit with respect to endometrial cancer risk reduction was only observed with higher lifetime physical activity (RR 0.77, 95%CI 0.67, 0.88), not with higher physical activity at a young age (RR 0.89, 95%CI 0.73, 1.07).

CONCLUSIONS

Being physically active over a lifetime, starting from early childhood, may lower the risks of developing breast cancer, colon cancer, and endometrial cancer.

Breast cancer in adolescents and young adults

Breast cancer is the most common cancer of adolescents and young adult (AYA) women aged 15 to 39 years, accounting for 5.6% of all invasive breast cancer in women. In comparison with older women, AYAs are more likely to have familial cancer predisposition genes, larger breast tumors, unfavorable biological characteristics, distant metastatic disease at diagnosis, and adverse outcome. Endocrine therapy and some chemotherapy recommendations differ between young and older women. AYAs require coordinated multidisciplinary care, treatment regimens that minimize late effects such as premature menopause and osteoporosis, and proactive management of psychological and sexual health during and after cancer treatment.

Alcohol, Physical Activity, Smoking, and Breast Cancer Subtypes in a Large, Nested Case-Control Study from the Norwegian Breast Cancer Screening Program

Background: To what extent alcohol, smoking, and physical activity are associated with the various subtypes of breast cancer is not clear. We took advantage of a large population-based screening cohort to determine whether these risk factors also increase the risk of the poor prognosis subtypes.Methods: We conducted a matched case-control study nested within the Norwegian Breast Cancer Screening Program during 2006-2014. A total of 4,402 breast cancer cases with risk factor and receptor data were identified. Five controls were matched to each case on year of birth and year of screening. Conditional logistic regression was used to estimate ORs of breast cancer subtypes adjusted for potential confounders.Results: There were 2,761 luminal A-like, 709 luminal B-like HER2-negative, 367 luminal B-like HER2-positive, 204 HER2-positive, and 361 triple-negative cancers. Current alcohol consumption was associated with breast cancer risk overall [OR 1.26; 95% confidence interval (CI), 1.09-1.45] comparing 6+ glasses a week to never drinkers. However, this risk increase was found only for luminal A-like breast cancer. Smoking 20+ cigarettes a day was associated with an OR of 1.41 (95% CI, 1.06-1.89) overall, with significant trends for luminal A-like and luminal B-like HER2-negative cancer. Current physical activity (4+ hours/week compared with none) was associated with 15% decreased risk of luminal A-like cancer, but not clearly with other subtypes.Conclusions: In this large study, alcohol, smoking, and physical activity were predominantly associated with luminal A-like breast cancer.Impact: Alcohol, smoking, and physical activity were associated with luminal A-like breast cancer subtype. Cancer Epidemiol Biomarkers Prev; 26(12); 1736-44. ©2017 AACR.

The Interaction between Genetic Ancestry and Breast Cancer Risk Factors among Hispanic Women: The Breast Cancer Health Disparities Study

Background: Hispanic women have lower breast cancer incidence rates than non-Hispanic white (NHW) women. To what extent genetic versus nongenetic factors account for this difference is unknown.Methods: Using logistic regression, we evaluated the interactive influences of established risk factors and ethnicity (self-identified and identified by ancestral informative markers) on breast cancer risk among 2,326 Hispanic and 1,854 NHW postmenopausal women from the United States and Mexico in the Breast Cancer Health Disparities Study.Results: The inverse association between the percentage of Native American (NA) ancestry and breast cancer risk was only slightly attenuated after adjusting for known risk factors [lowest versus highest quartile: odds ratio (OR) =1.39, 95% confidence interval (CI) = 1.00-1.92 among U.S. Hispanics; OR = 1.92 (95% CI, 1.29-2.86) among Mexican women]. The prevalence of several risk factors, as well as the associations with certain factors and breast cancer risk, differed according to genetic admixture. For example, higher body mass index (BMI) was associated with reduced risk among women with lower NA ancestry only [BMI <25 versus >30: OR = 0.65 (95% CI, 0.44-0.98) among U.S. Hispanics; OR = 0.53 (95% CI, 0.29-0.97) among Mexicans]. The average number of risk factors among cases was inversely related to the percentage of NA ancestry.Conclusions: The lower NA ancestry groups were more likely to have the established risk factors, with the exception of BMI. Although the majority of factors were associated with risk in the expected directions among all women, BMI had an inverse association among Hispanics with lower NA ancestry.Impact: These data suggest that the established risk factors are less relevant for breast cancer development among women with more NA ancestry. Cancer Epidemiol Biomarkers Prev; 26(5); 692-701. ©2016 AACR.

Psychosocial Variables Related to Why Women are Less Active than Men and Related Health Implications

This article reviews psychosocial influences on women’s participation in physical activity as they differ from men and how associated activity differences impact women’s risk for a number of chronic diseases. This topic directly aligns with the mission of this special edition related to disparities in women’s health as the typically lower level of physical activity in females directly impacts their health. On average, females participate in physical activity at lower rates than their male counterparts. These lower rates of physical activity are directly related to both incidence of and outcomes from cardiovascular disease, type 2 diabetes, and breast and gynecological cancers. The relationship between psychosocial factors that are understood to affect physical activity differs between men and women. Specifically, self-efficacy, social support, and motivation are empirically substantiated factors that found to impact physical activity participation among women differently than men. Understanding these relationships is integral to designing effective interventions to target physical activity participation in women so that the related health risks are adequately addressed.

Recreational physical activity and risk of triple negative breast cancer in the California Teachers Study

BACKGROUND

Evidence has accumulated showing that recreational physical activity reduces breast cancer risk. However, it is unclear whether risk reduction pertains to specific receptor-defined subtypes. Moreover, few studies have examined whether changes in the amount of recreational physical activity during adulthood influence breast cancer risk.

METHODS

A total of 108,907 women, ages 22 to 79 years with no history of breast cancer when joining the California Teachers Study in 1995-1996, completed a baseline questionnaire and were eligible for the study. Through 2012, 5882 women were diagnosed with invasive breast cancer. Breast cancer subtypes were defined by the expression status of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). Multivariable Cox proportional hazards models provided adjusted hazard ratios (HRs) and 95 % confidence intervals (CIs) for breast cancer overall and ER/PR/HER2-defined subtypes associated with long-term (from high school through age 54 or age at cohort entry, whichever was younger) and baseline (during 3 years prior to baseline) recreational physical activity. Among women who also completed a follow-up questionnaire at 10 years after baseline in 2005-2008 (54,686 women, 1406 with invasive breast cancer), risk associated with changes in the amount of recreational physical activity from baseline to the 10-year follow-up (during 3 years prior to the 10-year follow-up) was determined.

RESULTS

Both long-term and baseline strenuous recreational physical activity were inversely associated with risk of invasive breast cancer (P trend ≤0.03). The observed associations were mainly confined to women with triple negative breast cancer (TNBC, ER-/PR-/HER2-, P trend ≤0.02) or luminal A-like subtype (ER+ or PR+ plus HER2-) who were former users of menopausal hormone therapy at baseline (P trend = 0.02, P homogeneity of trends ≤0.03). Moreover, women who consistently engaged in the highest level (≥3.51 h/wk/y) of strenuous recreational physical activity between baseline and 10-year follow-up had the lowest risk of breast cancer (HR = 0.71, 95 % CI = 0.52-0.98) when compared to those who were consistently low (≤0.50 h/wk/y).

CONCLUSIONS

Strenuous recreational physical activity is associated with lower breast cancer risk, especially TNBC. The benefit may be maximized by consistently engaging in high-intensity recreational physical activity during adulthood.

Meeting or Exceeding Physical Activity Guidelines is Associated with Reduced Risk for Cancer in Mexican-Americans

BACKGROUND

Epidemiologic studies have shown that inadequate physical activity was associated with cancers in whites and other ethnic groups, but in Mexican-Americans data are limited. This study aimed to measure the association between physical activity and reported cancer risk in Mexican-Americans.

METHODS

Participants were drawn from the Cameron County Hispanic Cohort (n=3,391), a randomly selected Mexican-American cohort in Texas on the US-Mexico border. Physical activity was assessed using the International Physical Activity Questionnaire. Cancer was self-reported by the participants as being told by a health care provider that they had cancer.

RESULTS

Ninety-nine participants of the cohort (2.94%) reported a diagnosis of cancer. Compared to participants who did not meet US physical activity guidelines, subjects who met physical activity guidelines of 150 moderate and vigorous minutes per week (≥ 600 METs) reduced their risk for cancer by 87% (OR=0.13; 95% CI: 0.03-0.54), and subjects with total minutes per week of moderate and vigorous/strenuous activity greater than 745 METs decreased cancer risk by 86% [odds ratio (OR)=0.14; 95% confidence interval (CI): 0.03-0.60] comparing with their counterparts, after adjusting for age, gender, body mass index, smoking and alcohol drinking status, education and total portions of fruit and vegetable intake.

CONCLUSIONS

Meeting or exceeding recommended levels of moderate and vigorous physical activity was associated with a significantly reduced risk of reporting cancer by Mexican-Americans. Meeting or exceeding recommended levels of physical activity appears to be an effective target for cancer prevention and control among Mexican-Americans independent of BMI and other factors.

Reduced risk of breast cancer associated with recreational physical activity varies by HER2 status

Convincing epidemiologic evidence indicates that physical activity is inversely associated with breast cancer risk. Whether this association varies by the tumor protein expression status of the estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), or p53 is unclear. We evaluated the effects of recreational physical activity on risk of invasive breast cancer classified by the four biomarkers, fitting multivariable unconditional logistic regression models to data from 1195 case and 2012 control participants in the population-based Women’s Contraceptive and Reproductive Experiences Study. Self-reported recreational physical activity at different life periods was measured as average annual metabolic equivalents of energy expenditure [MET]-hours per week. Our biomarker-specific analyses showed that lifetime recreational physical activity was negatively associated with the risks of ER-positive (ER+) and of HER2-negative (HER2−) subtypes (both P_trend ≤ 0.04), but not with other subtypes (all P_trend > 0.10). Analyses using combinations of biomarkers indicated that risk of invasive breast cancer varied only by HER2 status. Risk of HER2–breast cancer decreased with increasing number of MET-hours of recreational physical activity in each specific life period examined, although some trend tests were only marginally statistically significant (all P_trend ≤ 0.06). The test for homogeneity of trends (HER2– vs. HER2+ ) reached statistical significance only when evaluating physical activity during the first 10 years after menarche (P_homogeneity = 0.03). Our data suggest that physical activity reduces risk of invasive breast cancers that lack HER2 overexpression, increasing our understanding of the biological mechanisms by which physical activity acts.

Dejavniki gibalne aktivnosti in z zdravjem povezane kakovosti življenja

Uvod: Gibalna aktivnost koristi telesnemu in duševnemu zdravju. Namen članka je ugotoviti dejavnike, ki vplivajo nanjo, in možne ukrepe za povečanje te dejavnosti. Cilj članka je spodbuditi strokovnjake s področij zdravja in športne dejavnosti k sodelovanju pri oblikovanju in izvajanju učinkovitih ukrepov za povečanje gibanja med prebivalstvom. Metode: Opravljen je bil pregled literature o dejavnikih, ki vplivajo na gibalno aktivnost in z zdravjem povezano kakovost življenja, ter o ukrepih, povezanih z njimi. V pregled so vključene raziskave, ki so objavljene v angleškem jeziku v obdobju 2000–2010 in evidentirane v Web of Science (SCI-EXPANDED ali SSCI). Članek povzema izsledke 46 objav, za potrebe teoretičnih izhodišč pa še dodatnih 43 objav. Rezultati: Na odločitev za gibanje vplivajo lastnosti posameznika in širšega družbenoekonomskega okolja. Bistveni so starost, spol in zdravstveni status posameznika. Pri posameznih skupinah populacije prepoznamo specifične dejavnike, ki vplivajo na odločitev za gibalno aktivnost. Učinkoviti ukrepi spodbujanja gibanja so zato usmerjeni na te skupine in izhajajo iz identificiranih dejavnikov. Diskusija in zaključek: Raznolikost omenjenih skupin in dejavnikov je osnova za načrtovanje preventivnih oziroma interventnih ukrepov. Smiselno je, da se pri organiziranju in izvajanju programov povežejo organizacije s področij zdravstva, športa in druge interesne skupine. Pri tem naj izkoristijo obstoječe zakonske okvire.

Influence of lifestyle factors on mammographic density in postmenopausal women

Background

Mammographic density is a strong risk factor for breast cancer. Apart from hormone replacement therapy (HRT), little is known about lifestyle factors that influence breast density.

Methods

We examined the effect of smoking, alcohol and physical activity on mammographic density in a population-based sample of postmenopausal women without breast cancer. Lifestyle factors were assessed by a questionnaire and percentage and area measures of mammographic density were measured using computer-assisted software. General linear models were used to assess the association between lifestyle factors and mammographic density and effect modification by body mass index (BMI) and HRT was studied.

Results

Overall, alcohol intake was positively associated with percent mammographic density (P trend  = 0.07). This association was modified by HRT use (P interaction  = 0.06): increasing alcohol intake was associated with increasing percent density in current HRT users (P trend  = 0.01) but not in non-current users (P trend  = 0.82). A similar interaction between alcohol and HRT was found for the absolute dense area, with a positive association being present in current HRT users only (P interaction  = 0.04). No differences in mammographic density were observed across categories of smoking and physical activity, neither overall nor in stratified analyses by BMI and HRT use.

Conclusions

Increasing alcohol intake is associated with an increase in mammography density, whereas smoking and physical activity do not seem to influence density. The observed interaction between alcohol and HRT may pose an opportunity for HRT users to lower their mammographic density and breast cancer risk.

Risk factors of breast cancer: a systematic review and meta-analysis

The etiology of breast cancer might be explained by 2 mechanisms, namely, differentiation and proliferation of breast epithelial cells mediated by hormonal factors. We performed a systematic review and meta-analysis to update effects of risk factors for both mechanisms. MEDLINE and EMBASE were searched up to January 2011. Studies that assessed association between oral contraceptives (OC), hormonal replacement therapy (HRT), diabetes mellitus (DM), or breastfeeding and breast cancer were eligible. Relative risks with their confidence intervals (CIs) were extracted. A random-effects method was applied for pooling the effect size. The pooled odds ratios of OC, HRT, and DM were 1.10 (95% CI = 1.03-1.18), 1.23 (95% CI = 1.21-1.25), and 1.14 (95% CI = 1.09-1.19), respectively, whereas the pooled odds ratio of ever-breastfeeding was 0.72 (95% CI = 0.58-0.89). Our study suggests that OC, HRT, and DM might increase risks, whereas breastfeeding might lower risks of breast cancer.

Dietary intake of folate, B-vitamins and methionine and breast cancer risk among Hispanic and non-Hispanic white women

Background

Low dietary folate intake is associated with several neoplasias, but reports are inconsistent for breast cancer. Additionally, the association of folate with breast cancer estrogen receptor (ER) status is not well established.

Objective

To determine if dietary intakes of folate, B-vitamins (B₂, B₆, B₁₂) and methionine are associated with breast cancer risk and ER status in Hispanic, and non-Hispanic White women in the southwestern US.

Materials and Methods

Primary breast cancer cases (n = 2,325) in the 4-Corners region (Arizona, Colorado, New Mexico and Utah), diagnosed between October 1999 and May 2004, were identified through state cancer registries. Controls (n = 2,525) were frequency-matched by ethnicity and age (±5 years). Dietary intake, physical activity and other exposures were assessed using in-person interviews. Risk was assessed through multivariable and multinomial logistic regression with adjustment for relevant covariates.

Result

While there was no overall association with breast cancer, the highest quartile of folate intake was marginally inversely associated with ER− breast cancer (Odds Ratio (OR) = 0.50, 95%CI 0.25–1.00, p for trend = 0.07). Vitamin B₁₂ intake was inversely associated with breast cancer also (OR = 0.73, 95%CI 0.53–1.00, p for trend = 0.06), particularly for the highest quartile of ER+ breast cancer (OR = 0.67, 95%CI 0.46–0.99, p for trend = 0.06), among NHW women (OR = 0.49, 95%CI 0.29–0.81, p for trend = 0.01) and invasive breast cancer (OR = 0.63; 95%CI: 0.42, 0.93, P_trend = 0.01). Methionine intake was also inversely associated with ER+ breast cancer (OR for 4^th quartile = 0.83, 95%CI 0.66–1.03, p for trend = 0.04), primarily among Hispanic women (OR = 0.71, 95%CI 0.47–1.06, and P for trend = 0.02).

Conclusion

Higher intake of folate is marginally associated with a lower risk for ER− breast cancer, and higher intakes of vitamin B-12 and methionine are marginally associated with a lower risk of ER+ breast cancer.

Differences between Hispanic and non-Hispanic white women with breast cancer for clinical characteristics and their correlates

PURPOSE

Body size and ethnicity may influence breast cancer tumor characteristics at diagnosis. We compared Hispanic and non-Hispanic white (NHW) cases for stage of disease, estrogen receptor (ER) status, tumor size, and lymph node status, and the associations of these with body size in the 4-Corners Breast Cancer Study.

METHODS

One thousand five hundred twenty-seven NHW and 798 Hispanic primary incident breast cancer cases diagnosed between October 1999 and May 2004 were included. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by multiple logistic regression.

RESULTS

Hispanic women were more likely to have larger (>1 cm) ER- tumors and more than four positive lymph nodes (P < .003). Lymph node status was not associated with body size. However, among NHW women, obesity (body mass index >30) and increased waist circumference (>38.5 inches) were significantly positively associated with ER- tumor status (OR, 1.87; 95% CI, 1.24-2.81 and OR, 2.59; 95% CI, 1.58-4.22, respectively). In contrast, among Hispanic women, obesity and waist circumference had inverse associations with ER- tumor status (OR, 0.49; 95% CI, 0.29-0.84 and OR, 0.56; 95% CI, 0.30-1.05, respectively).

CONCLUSIONS

Hispanic ethnicity may modify the association of body size and composition with ER- breast cancer. This finding could have relevance to clinical treatment and prognosis.

ADRB2 G-G haplotype associated with breast cancer risk among Hispanic and non-Hispanic white women: interaction with type 2 diabetes and obesity

INTRODUCTION

Polymorphisms in the beta-2-adrenergic receptor (ADRB2) gene have been studied in relation to risk of type 2 diabetes and obesity, risk factors that have received increased attention in relation to breast cancer. We evaluated the hypothesis that ADRB2 variants (rs1042713, rs1042714) are associated with breast cancer risk in non-Hispanic white (NHW) and Hispanic (H) women using data from a population-based case-control study conducted in the southwestern United States.

METHODS

Data on lifestyle and medical history, and blood samples, were collected during in-person interviews for incident primary breast cancer cases (1,244 NHW, 606 H) and controls (1,330 NHW, 728 H). ADRB2 genotypes for rs1042713(G/A) and rs1042714(G/C) were determined using TaqMan assays. The associations of each variant and corresponding haplotypes with breast cancer were estimated using multivariable logistic regression.

RESULTS

Two copies compared to one or zero copies of the ADRB2 G-G haplotype were associated with increased breast cancer risk for NHW women [odds ratio (OR), 1.95; 95 % confidence interval (95 % CI), 1.26-3.01], but with reduced risk for H women [OR, 0.74; 95 % CI, 0.50-1.09]. Effect estimates were strengthened for women with a body mass index (BMI) ≥25 kg/m(2) [H: OR, 0.50; 95 % CI, 0.31-0.82; NHW: OR, 3.85; 95 % CI, 1.88-7.88] and for H women with a history of diabetes [H: OR, 0.32; 95 % CI, 0.12-0.89].

CONCLUSIONS

These data suggest that ethnicity modifies the association between the ADRB2 G-G haplotype and breast cancer risk, and being overweight or obese enhances the divergence of risk between H and NHW women.

Risk and protective factors for breast cancer in Midwest of Brazil

Patterns of physical activity, body composition, and breastfeeding are closely related to health and are influenced by environmental, economic, and social factors. With the increase of sedentary lifestyle and overweight, many chronic diseases have also increased, including cancer. Breast cancer is the most common cancer in women worldwide, and the knowledge of its risk and protective factors is important to the adoption of primary prevention strategies. We aimed to investigate some risk and protective factors for breast cancer among women from Midwest Brazil. It is a case-control study of outpatient basis, carried out with 93 breast cancer cases and 186 controls. Socioeconomic, gynecological, anthropometric, and lifestyle variables were collected, and odds ratios (ORs) values were estimated (significance level, 5%; confidence interval (CI), 95%). Per capita income equal to or lower than 1/2 Brazilian minimum wage (OR = 1.88; CI = 1.06–3.29), residence in rural area (OR = 4.93; CI = 1.65–14.73), and presence of family history of breast cancer (OR = 5.38; CI = 1.46–19.93) are risk factors for breast cancer. In turn, physical activity (past 6 months) (OR = 0.23; CI = 0.10–0.55) and leisure physical activity at 20 years old (OR = 0.13; CI = 0.03–0.54) are protective factors for the disease in women who live in Midwest of Brazil.

Obesity, inflammation, and postmenopausal breast cancer: therapeutic implications

Breast cancer is the female malignant neoplasia with the highest incidence in the industrialized world. Although early diagnosis has contributed to therapeutic success, breast cancer remains a major health issue. In the last few year the hormone therapy for estrogen-dependent breast cancer has evolved achieving significant clinical results; at the same time, it has enabled us to better define the role of estrogens in the etiopathogenesis of this tumour. Weight increase and obesity have been identified as the most important risk and prognostic factors for breast cancer in postmenopausal women. Several hypotheses have been proposed to explain the association of obesity with postmenopausal breast cancer. Specific obesity-associated factors, including leptin, insulin and inflammatory mediators, seem to influence breast cancer growth and prognosis independently of estrogens and at least in part by interacting with estrogen signalling at a cellular level. Therefore, a careful assessment of the nutritional status and body composition is paramount for a proper therapeutic approach for postmenopausal breast carcinoma. The use of antidiabetic and anti-inflammatory drugs associated with conventional hormone therapies and dietary/physical interventions could offer a new therapeutic approach for breast carcinoma that develops in the context of adiposity.

Obesity is associated with breast cancer in African-American women but not Hispanic women in South Los Angeles

BACKGROUND

Obesity is considered a risk factor for breast cancer. Modifying life styles that reduce obesity offers the potential for prevention and improved outcomes from cancer. The effects of obesity and breast cancer among African-American women and Hispanic women have been explored in a limited number of studies. The objective of the current study was to investigate the association of obesity with breast cancer in a minority cohort.

METHODS

This was a cross-sectional study of 471 African-American and Hispanic women with and without breast cancer in South Los Angeles. Data regarding body mass index (BMI) and clinical factors were obtained by medical record abstraction. Data were assessed using logistic regression with multivariate analysis. Kaplan-Meier survival analysis was used to assess disease-free survival.

RESULTS

Women with breast cancer were more likely to be obese (BMI >30 kg/m(2)) than women without breast cancer (odds ratio [OR], 2.0; P = .01). There was a significant association of being overweight or obese and breast cancer among postmenopausal women (OR, 2.3 [P = .03] and 2.9 [P < .01], respectively). The association between obesity and breast cancer was significant only among African-American women (OR, 2.70; P < .01) and was especially significant among postmenopausal African-American women (OR, 4.8; P < .01). There was a borderline significant association between obesity and later disease stage at diagnosis (P = .06). An association also was observed between higher BMI (for cutoff points of both 30 kg/m(2) and 28 kg/m(2)) and poorer disease-free survival (P = .045 and P = .019, respectively).

CONCLUSIONS

The current data suggested an association between obesity and breast cancer, especially among postmenopausal women and most significantly in the African-American cohort.

Physical activity and breast cancer prevention

Breast cancer is the most commonly diagnosed invasive malignancy and the second leading cause of cancer death in women. This chapter considers epidemiologic evidence regarding the association between physical activity and breast cancer risk from 73 studies conducted around the world. Across these studies there was a 25% average risk reduction amongst physically active women as compared to the least active women. The associations were strongest for recreational activity, for activity sustained over the lifetime or done after menopause, and for activity that is of moderate to vigorous intensity and performed regularly. There is also some evidence for a stronger effect of physical activity amongst postmenopausal women, women who are normal weight, have no family history of breast cancer, and are parous. It is likely that physical activity is associated with decreased breast cancer risk via multiple interrelated biologic pathways that may involve adiposity, sex hormones, insulin resistance, adipokines, and chronic inflammation. Future research should include prospective observational epidemiologic studies relating proposed biomarkers to breast cancer risk and also randomized controlled trials to examine how physical activity influences the proposed biomarkers. Exercise trials will provide more clarity regarding the appropriate type, dose, and timing of activity that relate to breast cancer risk reduction.

Does hormone therapy counter the beneficial effects of physical activity on breast cancer risk in postmenopausal women?

Studies consistently demonstrate that physical activity is inversely associated with postmenopausal breast cancer. Whether this association is stronger among non-hormone users or former users of menopausal hormone therapy (HT) is of interest given the marked decline in HT use since 2002. The Women's Contraceptive and Reproductive Experiences Study, a population-based case-control study of invasive breast cancer, recruited white women and black women ages 35-64 years and collected histories of lifetime recreational physical activity and HT use including estrogen-alone therapy (ET) and estrogen plus progestin therapy (EPT). Among postmenopausal women (1,908 cases, 2,013 control participants), breast cancer risk declined with increasing levels of lifetime physical activity among never HT users; among short-term HT users (fewer than 5 years); and among current ET users; P (trend) values ranged from 0.004 to 0.016. In contrast, physical activity had no significant association with risk among long-term and past HT users and among current EPT users. No statistical evidence of heterogeneity was demonstrated for duration or currency of HT use. Breast cancer risk decreases with increasing lifetime physical activity levels among postmenopausal women who have not used HT, have used HT for less than 5 years, or are current ET users, yet this study was unable to demonstrate statistically that HT use modifies the relationship between physical activity and breast cancer. With profound changes in HT use occurring since 2002, it will be important in future studies to learn whether or not any association between physical activity and breast cancer among former HT users is a function of time since last HT use.

A systematic review of the evidence for Canada's Physical Activity Guidelines for Adults

This systematic review examines critically the scientific basis for Canada's Physical Activity Guide for Healthy Active Living for adults. Particular reference is given to the dose-response relationship between physical activity and premature all-cause mortality and seven chronic diseases (cardiovascular disease, stroke, hypertension, colon cancer, breast cancer, type 2 diabetes (diabetes mellitus) and osteoporosis). The strength of the relationship between physical activity and specific health outcomes is evaluated critically. Literature was obtained through searching electronic databases (e.g., MEDLINE, EMBASE), cross-referencing, and through the authors' knowledge of the area. For inclusion in our systematic review articles must have at least 3 levels of physical activity and the concomitant risk for each chronic disease. The quality of included studies was appraised using a modified Downs and Black tool. Through this search we identified a total of 254 articles that met the eligibility criteria related to premature all-cause mortality (N = 70), cardiovascular disease (N = 49), stroke (N = 25), hypertension (N = 12), colon cancer (N = 33), breast cancer (N = 43), type 2 diabetes (N = 20), and osteoporosis (N = 2). Overall, the current literature supports clearly the dose-response relationship between physical activity and the seven chronic conditions identified. Moreover, higher levels of physical activity reduce the risk for premature all-cause mortality. The current Canadian guidelines appear to be appropriate to reduce the risk for the seven chronic conditions identified above and all-cause mortality.

Adipose tissue as target organ in the treatment of hormone-dependent breast cancer: new therapeutic perspectives

Breast cancer is the female malignant neoplasia with the highest incidence in the industrialized world. Despite many undeniable therapeutic successes obtained, breast cancer still remains, however, a major health issue. In the last few years, thanks to aromatase inhibitors, the hormone therapy for oestrogen-dependent breast cancer has evolved in terms of efficacy and tolerability; at the same time, it has enabled us to better define the role of oestrogens in the etiopathogenesis of this tumour. Weight increase and obesity have been identified as the most important risk and prognostic factors for breast cancer in postmenopausal women. Several hypotheses have been proposed to explain the association of obesity with postmenopausal breast cancer. A more recent hypothesis suggests that adipocytes and their autocrine (paracrine and endocrine actions) are at the centre of such an etiopathogenetic mechanism. A better understanding of the main mechanisms that link together menopause, body-weight increase and hormone-dependent breast cancer is paramount to enable the identification of key molecules involved in the development of breast carcinoma and suggest new therapeutic options. The present review will discuss important findings on the therapeutic aspects of adipose tissue and adipokines as a target for treatment of hormone-dependent breast cancer.

Intensity and timing of physical activity in relation to postmenopausal breast cancer risk: the prospective NIH-AARP diet and health study

BACKGROUND

Despite strong evidence of an inverse association of physical activity with postmenopausal breast cancer risk, whether a certain intensity or time of life of physical activity is most effective for lowering breast cancer risk is not known.

METHODS

In 118,899 postmenopausal women in the prospective NIH-AARP Diet and Health Study, we examined the relations of light and moderate-to-vigorous intensity physical activity during four periods of life ("historical": ages 15-18, 19-29, 35-39 years; "recent": past 10 years) to postmenopausal breast cancer risk. Physical activity was assessed by self-report at baseline, and 4287 incident breast cancers were identified over 6.6 years of follow-up.

RESULTS

In age-adjusted and multivariate Cox regression models, >7 hours/week of moderate-to-vigorous activity during the past 10 years was associated with 16% reduced risk of postmenopausal breast cancer (RR:0.84; 95%CI:0.76,0.93) compared with inactivity. The association remained statistically significant after adjustment for BMI (RR:0.87; 95%CI:0.78,0.96). Neither moderate-to-vigorous activity during other periods of life nor light intensity activity during any period of life was related to breast cancer risk, and associations did not vary by tumor characteristics.

CONCLUSION

A high level of recent, but not historical, physical activity of moderate-to-vigorous intensity is associated with reduced postmenopausal breast cancer risk. More precise recall of recent physical activity than activity in the distant past is one possible explanation for our findings.

Characteristics associated with mammography screening among both Hispanic and non-Hispanic white women

AIMS

This study explores whether certain population characteristics are associated with adherence to mammography screening guidelines among Hispanic and non-Hispanic white (NHW) women living in the southwestern United States.

METHODS

Participants in a population-based study (4-Corners' Breast Cancer Study) included in this analysis were 790 Hispanic women and 1,441 NHW women. Multivariate logistic regression was used to compute the ethnic-specific adjusted odds ratios (OR) and 95% confidence intervals (CI) for the association of the outcome variable (adherent vs. nonadherent) and its correlates. Women were adherent if they had obtained their first mammogram between 41 and 50 years of age and had received at least one mammogram per 2 years or less.

RESULTS

Ethnic-specific associations were observed with certain population characteristics and mammography adherence. Specifically, characteristics that were significantly associated with adherence among Hispanic women were younger age (50-59 years), having a family history of breast cancer, nulliparity, hormone replacement therapy (HRT) use, nonsteroidal anti-inflammatory drug (NSAID) use, and performing regular breast self-examinations (BSE). Among NHW women, younger age (50-59 years), family history of breast cancer, obesity, consuming moderate amounts of alcohol, and taking HRT were associated with mammography adherence. When adjusting for the evaluated population characteristics, the relationship between ethnicity and mammography adherence was no longer apparent.

CONCLUSIONS

Ethnic-specific characteristics appear to explain differences in mammography adherence among Hispanic and NHW women. Disparities in screening rates, late-stage disease and breast cancer mortality that impact Hispanic women could potentially be addressed more effectively by interventions that specifically target the unique characteristics of the Hispanic population.

Breast cancer before age 40 years

Approximately 7% of women with breast cancer are diagnosed before the age of 40 years, and this disease accounts for more than 40% of all cancer in women in this age group. Survival rates are worse when compared to those in older women, and multivariate analysis has shown younger age to be an independent predictor of adverse outcome. Inherited syndromes, specifically BRCA1 and BRCA2, must be considered when developing treatment algorithms for younger women. Chemotherapy, endocrine, and local therapies have the potential to significantly impact both the physiologic health-including future fertility, premature menopause, and bone health-and the psychological health of young women as they face a diagnosis of breast cancer.

A prospective study of cardiorespiratory fitness and breast cancer mortality

PURPOSE

Physical activity may protect against breast cancer. Few prospective studies have evaluated breast cancer mortality in relation to cardiorespiratory fitness (CRF), an objective marker of physiologic response to physical activity habits.

METHODS

We examined the association between CRF and risk of death from breast cancer in the Aerobics Center Longitudinal Study. Women (N = 14,811), aged 20 to 83 yr with no prior breast cancer history, received a preventive medical examination at the Cooper Clinic in Dallas, Texas, between 1970 and 2001. Mortality surveillance was completed through December 31, 2003. CRF was quantified as maximal treadmill exercise test duration and was categorized for analysis as low (lowest 20% of exercise duration), moderate (middle 40%), and high (upper 40%). At baseline, all participants were able to complete the exercise test to at least 85% of their age-predicted maximal heart rate.

RESULTS

A total of 68 breast cancer deaths occurred during follow-up (mean = 16 yr). Age-adjusted breast cancer mortality rates per 10,000 woman-years were 4.4, 3.2, and 1.8 for low, moderate, and high CRF groups, respectively (trend P = 0.008). After further controlling for body mass index, smoking, drinking, chronic conditions, abnormal exercise ECG responses, family history of breast cancer, oral contraceptive use, and estrogen use, hazard ratios (95% CI) for breast cancer mortality across incremental CRF categories were 1.00 (referent), 0.67 (0.35-1.26), and 0.45 (0.22-0.95) (trend P = 0.04).

CONCLUSIONS

These results indicate that CRF is associated with a reduced risk of dying from breast cancer in women.

Physical activity and postmenopausal breast cancer: proposed biologic mechanisms and areas for future research

Convincing evidence now supports a probable preventive role for physical activity in postmenopausal breast cancer. The mechanisms by which long-term physical activity affect risk, however, remain unclear. The aims of this review were to propose a biological model whereby long-term physical activity lowers postmenopausal breast cancer risk and to highlight gaps in the epidemiologic literature. To address the second aim, we summarized epidemiologic literature on 10 proposed biomarkers, namely, body mass index (BMI), estrogens, androgens, sex hormone binding globulin, leptin, adiponectin, markers of insulin resistance, tumor necrosis factor-alpha, interleukin-6, and C-reactive protein, in relation to postmenopausal breast cancer risk and physical activity, respectively. Associations were deemed "convincing," "probable," "possible," or "hypothesized" using set criteria. Our proposed biological model illustrated the co-occurrence of overweight/obesity, insulin resistance, and chronic inflammation influencing cancer risk through interrelated mechanisms. The most convincing epidemiologic evidence supported associations between postmenopausal breast cancer risk and BMI, estrogens, and androgens, respectively. In relation to physical activity, associations were most convincing for BMI, estrone, insulin resistance, and C-reactive protein. Only BMI and estrone were convincingly (or probably) associated with both postmenopausal breast cancer risk and physical activity. There is a need for prospective cohort studies relating the proposed biomarkers to cancer risk and for long-term exercise randomized controlled trials comparing biomarker changes over time, specifically in postmenopausal women. Future etiologic studies should consider interactions among biomarkers, whereas exercise trials should explore exercise effects independently of weight loss, different exercise prescriptions, and effects on central adiposity.

Health and health behaviors among elderly Hispanic women

The purpose of this study was to describe and analyze the relationship between health and health behaviors among elderly Hispanic women who were lifetime U.S. residents. The number of elderly Hispanics is expected to grow faster than any other segment of the population within the United States. A random sample of 132 elderly Hispanic women enrolled in a health maintenance organization participated in this cross-sectional survey of health prevention, promotion, and protection behaviors and dimensions of health as measured by the Medical Outcomes Study Short Form-36. Results indicated that more than half of this group did not exercise regularly, one fourth did not eat regularly scheduled meals, and many had not participated in health screening. Among the women in this study, those whose lifestyles incorporated the more frequent practice of positive health behaviors also had better scores on 6 of the 8 specific health dimensions measured.

Physical activity and postmenopausal breast cancer risk in the NIH-AARP diet and health study

BACKGROUND

Although physical activity has been associated with reduced breast cancer risk, whether this association varies across breast cancer subtypes or is modified by reproductive and lifestyle factors is unclear.

METHODS

We examined physical activity in relation to postmenopausal breast cancer risk in 182,862 U.S. women in the NIH-AARP Diet and Health Study. Physical activity was assessed by self-report at baseline (1995-1996), and 6,609 incident breast cancers were identified through December 31, 2003. Cox regression was used to estimate the relative risk (RR) and 95% confidence interval (95% CI) of postmenopausal breast cancer overall and by tumor characteristics. Effect modification by select reproductive and lifestyle factors was also explored.

RESULTS

In multivariate models, the most active women experienced a 13% lower breast cancer risk versus inactive women (RR, 0.87; 95% CI, 0.81-0.95). This inverse relation was not modified by tumor stage or histology but was suggestively stronger for estrogen receptor (ER)-negative (RR, 0.75; 95% CI, 0.54-1.04) than ER-positive (RR, 0.97; 95% CI, 0.84-1.12) breast tumors and was suggestively stronger for overweight/obese (RR, 0.86; 95% CI, 0.77-0.96) than lean (RR, 0.95; 95% CI, 0.87-1.05) women. The inverse relation with physical activity was also more pronounced among women who had never used menopausal hormone therapy and those with a positive family history of breast cancer than their respective counterparts.

CONCLUSIONS

Physical activity was associated with reduced postmenopausal breast cancer risk, particular to ER-negative tumors. These results, along with heterogeneity in the physical activity-breast cancer relation for subgroups of menopausal hormone therapy use and adiposity, indicate that physical activity likely influences breast cancer risk via both estrogenic and estrogen-independent mechanisms.

Weight, dietary behavior, and physical activity in childhood and adolescence: implications for adult cancer risk

Lifestyle factors related to energy balance, including weight, dietary behavior and physical activity, are associated with cancer risk. The period of childhood and growth into adolescence and early adulthood may re-present a 'cumulative risk' for later adult-onset cancers. We review a number of epidemiologic studies that have examined associations among childhood and adolescent body size, diet, and physical activity with adult cancer risk. These studies suggest that unhealthy behaviors that develop early in life and persist over time may increase the risk of some cancer types, such as premenopausal breast, ovarian, endometrial, colon and renal cancer, adversely affect cancer-related morbidities, and increase mortality. Continued research is needed to further determine and refine how timing and degree of such exposures in early childhood and adolescence relate to adult cancer risk. Presently, sufficient evidence suggests a continued need for stronger primary prevention in cancer and obesity research via modified lifestyle behaviors earlier in the developmental spectrum, i.e. during childhood and adolescence.

Physical activity and premenopausal breast cancer: an examination of recall and selection bias

BACKGROUND

Compared with cohort studies, case-control investigations have tended to report clearer protective associations for the relationship between physical activity and premenopausal breast cancer risk.

METHODS

We conducted a case-control study within the Nurses' Health Study II cohort to examine whether recall or selection bias could explain the stronger protective associations. Self-reported total recreational physical activity during adulthood and over a woman's lifetime (ages 12 years to current) were assessed in 1997 before diagnosis and, again, from one to seven years after breast cancer diagnosis among the same women.

RESULTS

Eighty-seven percent of cases (417 of 479) and 82% of controls (390 of 474) responded. Selection bias was observed for activity during adulthood but not for activity over a woman's lifetime. Recall bias was not observed in the direction we expected: the odds ratios (ORs) for breast cancer comparing the highest versus lowest quintile of prospectively reported total activity were not significantly different than the corresponding estimates from retrospective reports (e.g., lifetime activity: prospective OR = 0.58, 95% CI: 0.37, 0.93 versus retrospective OR = 0.80; 95% CI: 0.50, 1.29).

CONCLUSION

Recall or selection bias may not have been accounted for protective associations among case-control investigations examining lifetime recreational physical activity and breast cancer. Selection bias related to recreational physical activity during adulthood and random error in the measurement of physical activity remain concerns.

Prospective study of physical activity and risk of postmenopausal breast cancer

INTRODUCTION

To prospectively examine the relation of total, vigorous and non-vigorous physical activity to postmenopausal breast cancer risk.

METHODS

We studied 32,269 women enrolled in the Breast Cancer Detection Demonstration Project Follow-up Study. Usual physical activity (including household, occupational and leisure activities) throughout the previous year was assessed at baseline using a self-administered questionnaire. Postmenopausal breast cancer cases were identified through self-reports, death certificates and linkage to state cancer registries. A Cox proportional hazards regression was used to estimate the relative risk and 95% confidence intervals of postmenopausal breast cancer associated with physical activity.

RESULTS

During 269,792 person-years of follow-up from 1987 to 1998, 1506 new incident cases of postmenopausal breast cancer were ascertained. After adjusting for potential risk factors of breast cancer, a weak inverse association between total physical activity and postmenopausal breast cancer was suggested (relative risk comparing extreme quintiles = 0.87; 95% confidence interval = 0.74 to 1.02; p for trend = 0.21). That relation was almost entirely contributed by vigorous activity (relative risk comparing extreme categories = 0.87; 95% confidence interval = 0.74 to 1.02; p for trend = 0.08). The inverse association with vigorous activity was limited to women who were lean (ie, body mass index <25.0 kg/m2: relative risk = 0.68; 95% confidence interval = 0.54 to 0.85). In contrast, no association with vigorous activity was noted among women who were overweight or obese (ie, body mass index > or = 25.0 kg/m2: relative risk = 1.18; 95% confidence interval = 0.93 to 1.49; p for interaction = 0.008). Non-vigorous activity showed no relation to breast cancer (relative risk comparing extreme quintiles = 1.02; 95% confidence interval = 0.87 to 1.19; p for trend = 0.86). The physical activity and breast cancer relation was not specific to a certain hormone receptor subtype.

CONCLUSIONS

In this cohort of postmenopausal women, breast cancer risk reduction appeared to be limited to vigorous forms of activity; it was apparent among normal weight women but not overweight women, and the relation did not vary by hormone receptor status. Our findings suggest that physical activity acts through underlying biological mechanisms that are independent of body weight control.

Physical activity and breast cancer risk among pre- and postmenopausal women in the U.S. Radiologic Technologists cohort

To clarify aspects of the association between physical activity and breast cancer, such as activity intensity required, and possible effect modification by factors such as menopausal hormone therapy (MHT) use. We prospectively examined physical activity in relation to breast cancer risk among 45,631 women participating in the U.S. Radiologic Technologists cohort. Participants provided information at baseline regarding hours spent per week engaging in strenuous activity, walking/hiking for exercise, and walking at home or work. We estimated multivariable relative risks (RR) and 95% confidence intervals (CI) of breast cancer using Cox regression. We identified 864 incident-invasive breast cancers. Greatest risk reduction was observed among women who reported walking/hiking for exercise 10 or more hours per week (RR, 0.57; 95% CI, 0.34-0.95) compared with those reporting no walking/hiking. The association between walking/hiking for exercise and breast cancer was modified by MHT use (p for interaction = 0.039). Postmenopausal women who never used MHT had reduced risks of breast cancer associated with physical activity whereas no relation was observed among ever users of MHT. Our study suggests moderate intensity physical activity, such as walking, may protect against breast cancer. Further, the relation between physical activity and breast cancer may be modified by MHT use.

Breast cancer incidence among American Indian and Alaska Native women: US, 1999-2004

BACKGROUND

Breast cancer is a leading cause of cancer morbidity and mortality among American Indian and Alaska Native (AI/AN) women. Although published studies have suggested that breast cancer rates among AI/AN women are lower than those among other racial and ethnic populations, accurate determinations of the breast cancer burden have been hampered by misclassification of AI/AN race.

METHODS

Cancer incidence data from the National Program of Cancer Registries and the Surveillance, Epidemiology, and End Results Program were combined to estimate age-adjusted rates for the diagnosis years 1999 through 2004. Several steps were taken to reduce the misclassification of AI/AN race: linking cases to Indian Health Service (IHS) patient services database, restricting analyses to Contract Health Service Delivery Area counties, and stratifying results by IHS region.

RESULTS

Breast cancer incidence rates among AI/AN women varied nearly 3-fold across IHS regions. The highest rates were in Alaska (134.8) and the Plains (Northern, 115.9; Southern, 115.7), and the lowest rates were in the Southwest (50.8). The rate in Alaska was similar to the rate among non-Hispanic white (NHW) women in Alaska. Overall, AI/AN women had lower rates of breast cancer than NHW women, but AI/AN women were more likely to be diagnosed with late-stage disease.

CONCLUSIONS

To the authors' knowledge, this report provides the most comprehensive breast cancer incidence data for AI/AN women to date. The wide regional variation indicates an important need for etiologic and health services research, and the large percentage of AI/AN women with late-stage disease demands innovative approaches for increasing access to screening.

A prospective study of age-specific physical activity and premenopausal breast cancer

BACKGROUND

Physical activity has been consistently associated with lower risk of postmenopausal breast cancer, but its relationship with premenopausal breast cancer is unclear. We investigated whether physical activity is associated with reduced incidence of premenopausal breast cancer, and, if so, what age period and intensity of activity are critical.

METHODS

A total of 64,777 premenopausal women in the Nurses' Health Study II reported, starting on the 1997 questionnaire, their leisure-time physical activity from age 12 to current age. Cox regression models were used to examine the relationship between physical activity, categorized by age period (adolescence, adulthood, and lifetime) and intensity (strenuous, moderate, walking, and total), and risk of invasive premenopausal breast cancer.

RESULTS

During 6 years of follow-up, 550 premenopausal women developed breast cancer. The strongest associations were for total leisure-time activity during participants' lifetimes rather than for any one intensity or age period. Active women engaging in 39 or more metabolic equivalent hours per week (MET-h/wk) of total activity on average during their lifetime had a 23% lower risk of premenopausal breast cancer (relative risk = 0.77; 95% confidence interval = 0.64 to 0.93) than women reporting less activity. This level of total activity is equivalent to 3.25 h/wk of running or 13 h/wk of walking. The age-adjusted incidence rates of breast cancer for the highest (> or = 54 MET-h/wk) and lowest (< 21 MET-h/wk) total lifetime physical activity categories were 136 and 194 per 100 000 person-years, respectively. High levels of physical activity during ages 12-22 years contributed most strongly to the association.

CONCLUSIONS

Leisure-time physical activity was associated with a reduced risk for premenopausal breast cancer in this cohort. Premenopausal women regularly engaging in high amounts of physical activity during both adolescence and adulthood may derive the most benefit.

Modifying effects of IL-6 polymorphisms on body size-associated breast cancer risk

OBJECTIVE

The association between obesity and breast cancer risk is complex. We examined whether the association between body size and breast cancer risk is modified by interleukin-6 (IL6) genotype.

METHODS AND PROCEDURES

Five polymorphisms in the IL-6 gene (rs1800797/-596A>G, rs1800796/-572G>C, rs1800795/-174G>C, rs2069832/IVS2G>A, and rs2069849 exon 5 C>T) were studied. We investigated IL6 genotypes and haplotypes with indicators of body size among non-Hispanic white (NHW) and Hispanic/American Indian (AI) breast cancer cases and controls living in the Southwestern United States.

RESULTS

We observed lower mean levels of BMI among NHW women who carried one or two copies of the GGCAC haplotype (in order: rs1800797, rs1800796, rs1800795, rs2069832, and rs2069849; P trend 0.02). This haplotype, with an estimated frequency of 43% in NHW study controls, was considerably less common in Hispanic/AI controls (19%). We did not detect significant interactions between IL6 genotypes or haplotypes and BMI categorized as low/normal (<25), overweight (25 to <30), or obese (> or =30) and breast cancer risk in either NHW or Hispanic/AI women. However, we detected consistent and significant interactions between waist-to-hip ratio (WHR) and IL6 rs1800795/-174 G>C genotype for breast cancer risk. These associations were restricted to postmenopausal NHW women. Among women without recent hormone exposure, those with a WHR >0.9 and the rs1800795 GG genotype had a greater than threefold increased risk of breast cancer (odds ratios (ORs) 3.22, 95% confidence intervals (CIs) 1.27, 817) when compared with women with a WHR <0.8 and the rs1800795 GG genotype (P interaction 0.01).

DISCUSSION

These data suggest that IL-6 genotypes may influence breast cancer risk in conjunction with central adiposity.