Physical activity and postmenopausal breast cancer: effect modification by breast cancer subtypes and effective periods in life

Determinants of persistent smoking among breast cancer survivors

INTRODUCTION

While quitting cigarette smoking can improve cancer treatment outcomes, many cancer patients continue to smoke post-diagnosis. The aim of this study was to examine factors associated with persistent cigarette use in postmenopausal women diagnosed with breast cancer, a cancer not traditionally thought of as tobacco-related.

METHODS

We used data of breast cancer patients who were recruited into the MARIE Study (Mamma Carcinoma Risk Factor Investigation) in Germany between 2002 and 2005 and followed up in 2009. This analysis was based on 450 study participants who reported active cigarette smoking at the time of diagnosis and participated in the follow-up interview. Logistic regression analyses were conducted to examine the association of sociodemographic characteristics, health behaviors, medical factors, and cancer treatment types with persistent smoking behavior.

RESULTS

At an average of 5.9 years (SD = 1.2) after diagnosis, 244 (54.2%) breast cancer survivors were still smoking cigarettes at follow-up. A longer duration of smoking (OR = 1.04, 95% CI = 1.01-1.06) and smoking on average ≥10 cigarettes per day (OR = 1.52, 95% CI = 1.02-2.28) increased the likelihood of persistent smoking, whereas increasing age (OR = 0.94, 95% CI = 0.90-0.97) and high engagement in leisure time physical activity (≥62 MET-hrs/wk: OR = 0.55, 95% CI = 0.32-0.98) were associated with quitting.

CONCLUSION

Smoking cessation programs in cancer care are needed. Specifically for breast cancer patients, tobacco treatment plans that include physical activity may be particularly helpful in quitting smoking cigarettes.

Long-Term Exposure to Walkable Residential Neighborhoods and Risk of Obesity-Related Cancer in the New York University Women's Health Study (NYUWHS)

BACKGROUND

Living in neighborhoods with higher levels of walkability has been associated with a reduced risk of obesity and higher levels of physical activity. Obesity has been linked to increased risk of 13 cancers in women. However, long-term prospective studies of neighborhood walkability and risk for obesity-related cancer are scarce.

OBJECTIVES

We evaluated the association between long-term average neighborhood walkability and obesity-related cancer risk in women.

METHODS

The New York University Women's Health Study (NYUWHS) is a prospective cohort with 14,274 women recruited between 1985 and 1991 in New York City and followed over nearly three decades. We geocoded residential addresses for each participant throughout follow-up and calculated an average annual measure of neighborhood walkability across years of follow-up using data on population density and accessibility to destinations associated with geocoded residential addresses. We used ICD-9 codes to characterize first primary obesity-related cancers and employed Cox proportional hazards models to assess the association between average neighborhood walkability and risk of overall and site-specific obesity-related cancers.

RESULTS

Residing in neighborhoods with a higher walkability level was associated with a reduced risk of overall and site-specific obesity-related cancers. The hazards ratios associated with a 1-standard deviation increase in average annual neighborhood walkability were 0.88 (95% CI: 0.85, 0.93) for overall obesity-related cancer, 0.89 (95% CI: 0.84, 0.95) for postmenopausal breast cancer, 0.82 (95% CI: 0.68, 0.99) for ovarian cancer, 0.87 (95% CI: 0.76, 0.99) for endometrial cancer, and 0.68 (95% CI: 0.49, 0.94) for multiple myeloma, adjusting for potential confounders at both the individual and neighborhood level. The association between neighborhood walkability and risk of overall obesity-related cancer was stronger among women living in neighborhoods with higher levels of poverty compared with women living in areas with lower poverty levels (p Interaction = 0.006 ).

DISCUSSION

Our study highlights a potential protective role of neighborhood walkability in preventing obesity-related cancers in women. https://doi.org/10.1289/EHP11538.

Associations between Pre-Diagnostic Physical Activity with Breast Cancer Characteristics and Survival

Physical activity (PA) is known to reduce breast cancer (BC) risk and improve patient prognosis. However, the association between pre-diagnostic PA and the aggressiveness of BC is unclear. We investigated the associations between PA, BC tumour characteristics, and survival. This retrospective observational study included 7688 BC patients from the Singapore Breast Cancer Cohort (2010−2016). PA information from the questionnaire included intensity (light/moderate/vigorous) and duration (<1 h/1−2 h/>2 h per week). A PA score (1−5) incorporating intensity and duration was calculated. Associations between PA score and tumour characteristics such as stage, histological grade, nodal and hormone receptor status were examined using multinomial regression. Moreover, 10-year overall survival was estimated using Cox regression analysis in 6572 patients after excluding patients with invalid survival data and stage IV disease. Breast tumours associated with higher PA score were more likely to be non-invasive (ORinvasive vs. non-invasive(reference) [95% CI]: 0.71 [0.58−0.87], p-trend = 0.001), of lower grade (ORpoorly vs. well differentiated(reference): 0.69 [0.52−0.93], p = 0.014), ER-positive (ORER-negative vs. ER-positive(reference): 0.94 [0.89−1.00], p-trend = 0.049), PR-positive (ORPR-negative vs. PR-positive(reference): 0.82 [0.67−0.99], p = 0.041), HER2-negative (ORHER2-negative vs. HER2-positive(reference): 1.29 [1.02−1.62], p-trend = 0.002), and less likely to be of HER2-overexpressed subtype (ORHER2-overexpressed vs. Luminal A(reference): 0.89 [0.81−0.98], p-trend = 0.018). These associations (odds ratios) were more pronounced among post-menopausal patients. A higher PA score did not improve survival. Higher levels of pre-diagnostic PA were associated with less aggressive tumours in BC patients. This illustrated another benefit of PA in addition to its known role in BC risk reduction.

Impact of body mass index, smoking habit, alcohol consumption, physical activity and parity on disease course of women with triple-negative breast cancer

OBJECTIVE

To evaluate the potential impact of body mass index (BMI), smoking habit, alcohol consumption, physical activity and parity on disease course of women with triple-negative breast cancer (TNBC).

MATERIAL AND METHODS

This was a retrospective chart analysis of patients with TNBC. Primary target parameters were overall survival (OS) and disease-free survival (DFS) depending on BMI, smoking habit, alcohol consumption, physical activity and parity. Results were descriptively evaluated and plotted as Kaplan-Meier curves. The null hypothesis was tested using the non-parametric log-rank test. All patients were treated at the University Medical School of Saarland, Dept of Gynecology, Obstetrics and Reproductive Medicine.

RESULTS

A total of 197 patients were analyzed. More than 50% of women were 40-60 years old (mean 57 years) and had a normal BMI. More than 88% of patients had either a T1 or T2 tumor, 64% were N0 and 66.5% had a G3 cancer. Thirty-four of 84 patients (40.38%) on neo-adjuvant chemotherapy reached a pathology-confirmed complete remission. During the follow-up (median 41.43 months), 34 (17.3%) patients had recurrent disease and 51 (25.9%) suffered from metastases. A total of 51 (25.9%) finally deceased. OS and DFS were not significantly impacted by BMI (OS: p = 0.4720; DFS: p = 0.2272), smoking habit (p = 0.9892; p = 0.6040), alcohol consumption (p = 0.6515; p = 0.7460), physical activity (p = 0.3320; p = 0.5991) or parity (p = 0.5929; 0.1417).

CONCLUSION

BMI, smoking habit, alcohol consumption, physical activity and parity had no impact on OS or DFS in women with TNBC.

Proceedings of the fourth international molecular pathological epidemiology (MPE) meeting

An important premise of epidemiology is that individuals with the same disease share similar underlying etiologies and clinical outcomes. In the past few decades, our knowledge of disease pathogenesis has improved, and disease classification systems have evolved to the point where no complex disease processes are considered homogenous. As a result, pathology and epidemiology have been integrated into the single, unified field of molecular pathological epidemiology (MPE). Advancing integrative molecular and population-level health sciences and addressing the unique research challenges specific to the field of MPE necessitates assembling experts in diverse fields, including epidemiology, pathology, biostatistics, computational biology, bioinformatics, genomics, immunology, and nutritional and environmental sciences. Integrating these seemingly divergent fields can lead to a greater understanding of pathogenic processes. The International MPE Meeting Series fosters discussion that addresses the specific research questions and challenges in this emerging field. The purpose of the meeting series is to: discuss novel methods to integrate pathology and epidemiology; discuss studies that provide pathogenic insights into population impact; and educate next-generation scientists. Herein, we share the proceedings of the Fourth International MPE Meeting, held in Boston, MA, USA, on 30 May-1 June, 2018. Major themes of this meeting included 'integrated genetic and molecular pathologic epidemiology', 'immunology-MPE', and 'novel disease phenotyping'. The key priority areas for future research identified by meeting attendees included integration of tumor immunology and cancer disparities into epidemiologic studies, further collaboration between computational and population-level scientists to gain new insight on exposure-disease associations, and future pooling projects of studies with comparable data.

Validation of inflammatory genetic variants associated with long-term cancer related fatigue in a large breast cancer cohort

BACKGROUND

Studies to date have reported several associations between single nucleotide polymorphisms (SNPs) and cancer related fatigue (CRF), but have been limited by small sample sizes, missing adjustment for relevant covariates or multiple testing, as well as varying CRF definitions, i.e. time and method of assessment. This study aimed to validate previously reported associations using the largest independent breast cancer sample to date and to evaluate further functional cytokine variants in relation to total CRF and all relevant CRF subdomains (physical, cognitive, and affective CRF).

METHOD

45 candidate SNPs in inflammatory pathway genes were selected based on previous reports (16 SNPs) or regulatory function (29 SNPs). Breast cancer patients recruited between 2002 and 2005 provided information on CRF at first follow-up (FU1) (N = 1389) and second follow-up (FU2) (N = 950), a median of 6.2 years and 11.7 years respectively after diagnosis. SNP associations were assessed using linear regression models on CRF scores separately for FU1 and FU2. Additionally, patients with persistent fatigue (fatigued at both time-points) were compared to those never fatigued using logistic regression models (N = 684). All analyses were adjusted for relevant covariates. Secondary analyses were conducted for CRF subdomains.

RESULTS

For total CRF none of the previously reported associations were confirmed after correction for multiple testing. The p-value distribution of all SNPs was not different than the one expected by chance. Analyses of CRF subdomains yielded a significant association between TNF-α rs3093662 and persistent physical CRF (Odds Ratio (OR) = 3.23, 95% Confidence Interval (CI) = 1.71-6.10, p = 0.0003).

CONCLUSION

We were unable to confirm previously reported findings, suggesting that individual SNPs are unlikely to be of clinical utility. Further investigations in well powered studies are warranted, which consider genetic heterogeneity according to subdomains of CRF.

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.

Does obesity modify the relationship between physical activity and breast cancer risk?

PURPOSE

With only 5-10% of breast cancer cases attributed to genetic inheritance, prevention efforts have focused on modifiable risk factors. Physical activity plays a role in reducing breast cancer risk; however, the interaction between physical activity and other modifiable risk factors, such as obesity, has received little attention.

METHODS

A systematic review and meta-analysis was conducted of studies examining the relationship between physical activity and breast cancer and how it may be modified by body mass index (BMI).

RESULTS

A total of 29 papers were included: 18 were cohort and 11 were case-control studies. Overall, a significant reduction in the relative risk of breast cancer was found in postmenopausal women with high versus low levels of physical activity for women with a BMI <25 kg/m² (RR 0.85, 95% CI 0.79, 0.92) and ≥25 kg/m² (RR 0.87, 95% CI 0.81, 0.93) but not ≥30 kg/m² (RR: 0.93, 95% CI 0.76, 1.13). Physical activity was not associated with a significant reduction in risk of breast cancer in premenopausal women in any BMI group.

CONCLUSION

The results of this meta-analysis suggest that physical activity is associated with a larger breast cancer risk reduction among women who are normal weight or overweight than among women who are obese. Since the included studies used diverse methods for assessment of physical activity and categories of BMI, results should be interpreted with caution and additional work is needed.

SOX2 regulates multiple malignant processes of breast cancer development through the SOX2/miR-181a-5p, miR-30e-5p/TUSC3 axis

BACKGROUND

High levels of SOX2 protein are correlated with increased dissemination of breast cancer. However, the underlying molecular mechanisms are not fully understood.

METHODS

In this study we investigate the role of SOX2 in breast cancer metastasis using multiple in vitro and in vivo assays including cell culture, shRNA-mediated knockdown, wound healing, colony formation, transwell chamber, xenograft and tail vein injection. Moreover, western blot, immunostaining, microarray and real-time PCR were used to determine the change of protein and miRNA levels. Luciferase assays were also used to evaluate activity which TUSC3 is a target of miR-181a-5p and miR-30e-5p, and the clinical survival relevance was analyzed by Kaplan-Meier analysis.

RESULTS

We identified a novel pathway involving SOX2 regulation of microRNAs to control the proliferation and migration of breast cancer cells. shRNA-mediated knockdown of SOX2 inhibits breast cancer cell expansion and migration. More importantly, we found that these changes are accompanied by significant reduction in the levels of two microRNAs, miR-181a-5p and miR-30e-5p. Overexpression of these two microRNAs leads to reduced protein levels of Tumor Suppressor Candidate 3 (TUSC3) in breast cancer cells; mutations of the potential binding sites in the 3'-UTR of TUSC3 abrogate the inhibitory effects of the microRNAs. We further found that upregulation of TUSC3 expression leads to reduced proliferation and migration of breast cancer cells. In human breast cancer samples the levels of TUSC3 protein are inversely correlated with those of SOX2 protein.

CONCLUSIONS

Taken together, our work reveals a novel SOX2-mediated regulatory axis that plays critical roles in the proliferation, migration and invasiveness of breast cancer cells. Targeting this axis may provide beneficial effect in the treatment of breast cancer.

Up to one-third of breast cancer cases in post-menopausal Mediterranean women might be avoided by modifying lifestyle habits: the EPIC Italy study

PURPOSE

Breast cancer (BC) is the most frequent cancer among women in developed countries. Physical activity (PA), body mass index (BMI), and alcohol intake have been identified as relevant lifestyle modifiable risk factors for post-menopausal BC. We aimed to evaluate the role of these factors in modulating post-menopausal BC risk and to estimate the proportion of BC cases attributable to low PA, high BMI, and alcohol taking into account non-modifiable factors.

METHODS

In the Italian section of the EPIC study, 15,010 post-menopausal women were recruited and provided information about dietary and lifestyle habits including PA, smoking, reproductive history, and anthropometric measurements. During 14.8 years of median follow-up, 672 incident BC cases (607 invasive and 65 in situ) were identified.

RESULTS

In multivariate models, inverse associations with BC risk emerged for increasing level of total (p trend 0.02), leisure time (p trend 0.04), and occupational (p trend 0.007) PA. High BMI (HR 1.21; 95% CI 1.02-1.43 and HR 1.33; 95% CI 1.06-1.65 for overweight and obesity, respectively) and alcohol consumption higher than 10 g/day (HR 1.30; 95% CI 1.09-1.54) were associated with BC risk. We estimated that 30% (95% CI 8-50%) of post-menopausal BC cases would be avoided through an increase of leisure time PA, a BMI below 25.0, and consuming no more than one drink/day.

CONCLUSIONS

This large study carried out in Mediterranean women confirms the role of PA, BMI, and alcohol consumption in modulating post-menopausal BC risk and supports the potential benefits obtainable by modifying these lifestyle factors.

Vigorous physical activity and risk of breast cancer in the African American breast cancer epidemiology and risk consortium

The relationship between physical activity and breast cancer risk has been extensively studied among women of European descent, with most studies reporting inverse associations. However, data on American women of African ancestry (AA) and by tumor subtypes are sparse. Thus, we examined associations of vigorous exercise and breast cancer risk overall, and by estrogen receptor (ER) status, in the African American Breast Cancer Epidemiology and Risk Consortium. We pooled data from four large studies on 2482 ER+ cases, 1374 ER- cases, and 16,959 controls. Multivariable logistic regression was used to compute odds ratios (OR) and 95 % confidence intervals (CI) for the risk of breast cancer overall, and polytomous logistic regression was used to model the risk of ER+ and ER- cancer. Recent vigorous exercise was associated with a statistically significant, modestly decreased risk for breast cancer overall (OR 0.88, 95 % CI 0.81-0.96) and for ER+ cancer (OR 0.88, 95 % CI 0.80-0.98), but not for ER- cancer (OR 0.93, 95 % CI 0.82-1.06). Overall, there was no strong evidence of effect modification by age, menopausal status, body mass index, and parity. However, our data were suggestive of modification by family history, such that an inverse association was present among women without a family history but not among those with a relative affected by breast cancer. Results from this large pooled analysis provide evidence that vigorous physical activity is associated with a modestly reduced risk of breast cancer in AA women, specifically ER+ cancer.

Physical Activity and Cancer Outcomes: A Precision Medicine Approach

There is increasing interest in applying a precision medicine approach to understanding exercise as a potential treatment for cancer. We aimed to inform this new approach by appraising epidemiologic literature relating postdiagnosis physical activity to cancer outcomes overall and by molecular/genetic subgroups. Across 26 studies of breast, colorectal, and prostate cancer patients, a 37% reduction was seen in risk of cancer-specific mortality, comparing the most versus the least active patients (pooled relative risk = 0.63; 95% confidence interval: 0.54-0.73). Risks of recurrence or recurrence/cancer-specific death (combined outcome) were also reduced based on fewer studies. We identified ten studies of associations between physical activity and cancer outcomes by molecular or genetic markers. Two studies showed statistically significant risk reductions in breast cancer mortality/recurrence for the most (versus least) physically active estrogen receptor-positive/progesterone receptor-positive (ER⁺/PR⁺) patients, while others showed risk reductions among ER^-PR^- and triple-negative patients. In colorectal cancer, four studies showed statistically significant risk reductions in cancer-specific mortality for patients with high (versus low) physical activity and P21 expression, P27 expression, nuclear CTNNB1^-, PTGS2 (COX-2)⁺, or IRS1 low/negative status. One prostate cancer study showed effect modification by Gleason score. As a means to enhance this evidence, future observational studies are needed that will measure physical activity objectively before and after diagnosis, use standardized definitions for outcomes, control for competing risks, assess nonlinear dose-response relations, and consider reverse causality. Ultimately, randomized controlled trials with clinical cancer outcomes and a correlative component will provide the best evidence of causality, relating exercise to cancer outcomes, overall and for molecular and genetic subgroups. Clin Cancer Res; 22(19); 4766-75. ©2016 AACR.

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.

Body mass index and risk of luminal, HER2-overexpressing, and triple negative breast cancer

Triple negative (TN, tumors that do not express estrogen receptor (ER), progesterone receptor (PR), or human epidermal growth factor receptor 2 (HER2)) and HER2-overexpressing (H2E, ER-/HER2+) tumors are two particularly aggressive subtypes of breast cancer. There is a lack of knowledge regarding the etiologies of these cancers and in particular how anthropometric factors are related to risk. We conducted a population-based case-case study consisting of 2659 women aged 20-69 years diagnosed with invasive breast cancer from 2004 to 2012. Four case groups defined based on joint ER/PR/HER2 status were included: TN, H2E, luminal A (ER+/HER2-), and luminal B (ER+/HER2+). Polytomous logistic regression was used to estimate odds ratios (ORs) and associated 95 % confidence intervals (CIs) where luminal A patients served as the reference group. Obese premenopausal women [body mass index (BMI) ≥30 kg/m(2)] had an 82 % (95 % CI 1.32-2.51) increased risk of TN breast cancer compared to women whose BMI <25 kg/m(2), and those in the highest weight quartile (quartiles were categorized based on the distribution among luminal A patients) had a 79 % (95 % CI 1.23-2.64) increased risk of TN disease compared to those in the lowest quartile. Among postmenopausal women obesity was associated with reduced risks of both TN (OR = 0.74, 95 % CI 0.54-1.00) and H2E (OR = 0.47, 95 % CI 0.32-0.69) cancers. Our results suggest obesity has divergent impacts on risk of aggressive subtypes of breast cancer in premenopausal versus postmenopausal women, which may contribute to the higher incidence rates of TN cancers observed among younger African American and Hispanic women.

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.

Lobular breast cancer: incidence and genetic and non-genetic risk factors

While most invasive breast cancers consist of carcinomas of the ductal type, about 10% are invasive lobular carcinomas. Invasive lobular and ductal carcinomas differ with respect to risk factors. Invasive lobular carcinoma is more strongly associated with exposure to female hormones, and therefore its incidence is more subject to variation. This is illustrated by US figures during the 1987 to 2004 period: after 12 years of increases, breast cancer incidence declined steadily from 1999 to 2004, reflecting among other causes the decreasing use of menopausal hormone therapy, and these variations were stronger for invasive lobular than for invasive ductal carcinoma. Similarly, invasive lobular carcinoma is more strongly associated with early menarche, late menopause and late age at first birth. As for genetic risk factors, four high-penetrance genes are tested in clinical practice when genetic susceptibility to breast cancer is suspected, BRCA1, BRCA2, TP53 and CDH1. Germline mutations in BRCA1 and TP53 are predominantly associated with invasive ductal carcinoma, while BRCA2 mutations are associated with both ductal and lobular cancers. CDH1, the gene coding for the E-cadherin adhesion protein, is of special interest as mutations are associated with invasive lobular carcinoma, but never with ductal carcinoma. It was initially known as the main susceptibility gene for gastric cancer of the diffuse type, but the excess of breast cancers of the lobular type in CDH1 families led researchers to identify it also as a susceptibility gene for invasive lobular carcinoma. The risk of invasive lobular carcinoma is high in female mutation carriers, as about 50% are expected to develop the disease. Carriers must therefore undergo intensive breast cancer screening, with, for example, yearly magnetic resonance imaging and mammogram starting at age 30 years.

Physical activity and the risk of postmenopausal breast cancer - the Norwegian Women and Cancer Study

Background

The relationship between physical activity (PA) throughout life and the risk of postmenopausal breast cancer overall and by estrogen receptor (ER) and progesterone receptor (PR) status, has been reported, but without consistent results. The present study aimed to investigate PA from young age to adulthood in participants of the Norwegian Women and Cancer (NOWAC) Study, in order to determine whether changes in PA level affect the risk of postmenopausal breast cancer.

Methods

1767 invasive breast cancer cases were identified among 80,202 postmenopausal participants of the NOWAC Study during 8.2 years of median follow-up. PA levels at age 14 years, 30 years and at cohort enrollment were obtained via a self-administered questionnaire. Multivariate Cox proportional hazard regression models were used to estimate relative risks and 95% confidence intervals of the risk of postmenopausal breast cancer overall and by ER/PR status.

Results

Risk of postmenopausal breast cancer overall and by ER/PR status was not associated with physical activity level at enrollment. Women with a low PA level at age 30 had an increased risk of ER+/PR + breast tumors (P for trend = 0.04) compared to women with a moderate physical activity level at age 30. Women with a low physical activity level at all three periods of life had a 20% significantly reduced risk of postmenopausal breast cancer, as well as a reduced risk of ER+/PR + and ER+/PR- breast tumors, compared with women who maintained a moderate physical activity level. However, when analyses were corrected for multiple tests, the result was no longer statistically significant. The findings were consistent over strata of age, body mass index and use of hormone replacement therapy.

Conclusions

The study results from this large Norwegian cohort do not support an association between physical activity at different periods of life and the risk of postmenopausal breast cancer.

Interview: Identifying lifestyle and genetic risk factors for breast cancer counseling and management

Jenny Chang-Claude speaks to Marco De Ambrogi, Commissioning Editor: Jenny Chang-Claude is Head of the Unit of Genetic Epidemiology in the Division of Cancer Epidemiology and also is the Deputy Head of the Division of Cancer Epidemiology at the German Cancer Research Center (Heidelberg, Germany). Since 2004 she has been Professor in Epidemiology at the University of Heidelberg (Heidelberg, Germany). Chang-Claude has one of the leading research groups in genetic epidemiology of breast cancer in Germany, with collaborations both nationally and internationally. She has conducted multicenter case–control studies and cohort follow-up studies in Germany, with a research focus on the identification of lifestyle and genetic determinants for risk and prognosis of breast and colorectal cancer, and gene–environmental interactions. Additional research includes studies on cancer survivorship and radiosensitivity. She is also actively involved in research activities of international consortia on breast, ovarian and colorectal cancer. Chang-Claude serves on international scientific advisory boards, committees and editorial boards. She is a (co)author of more than 350 scientific papers published in international scientific journals.

Exercise in the prevention and rehabilitation of breast cancer

Breast cancer is the most common type of cancer among women worldwide. Several epidemiological studies have shown an inverse relationship between the risk of breast cancer and physical activity levels, whereas exercise training has been recognized as a significant means in the rehabilitation process of breast cancer survivors. The relative risk reduction of breast cancer for women who engaged in moderate to vigorous physical activity for 3-5 days peek week ranged between 20-40 %. Furthermore, several studies demonstrated a 24-67 % reduction in the risk of total deaths and 50-53 % reduction in the risk of breast cancer deaths in women who are physically active after breast cancer diagnosis compared with sedentary women. Breast cancer survivors should be encouraged to participate in rehabilitation programs in order to obtain numerous physiological and psychological benefits. These include reductions in fatigue and improvements in immune function, physical functioning, body composition, and quality of life. Based on recent scientific evidence, a complete rehabilitation program for patients with breast cancer should combine both strength and aerobic exercise in order to maximize the expected benefits.

Association of pre-diagnosis physical activity with recurrence and mortality among women with breast cancer

Evidence is emerging that physical activity (PA) may improve overall survival after breast cancer diagnosis. However, the effect of PA on breast cancer recurrence and on cause-specific mortality is less investigated. We assessed the association of pre-diagnosis PA with recurrence, overall and cause-specific survival in a prospective cohort study in Germany including 3,393 non-metastatic breast cancer patients aged 50-74 years. Cox proportional hazards models were calculated adjusted for relevant prognostic factors. During a median follow-up of 5.6 years, 367 patients deceased. Overall mortality was significantly inversely associated with pre-diagnosis recreational PA. However, this effect was mainly attributed to deaths due to causes other than breast cancer. Multiple fractional polynomial analyses yielded a nonlinear association with markedly increased non-breast cancer mortality for women who did not engage in any sports or cycling in the years before the breast cancer diagnosis with a hazard ratio (HR, none vs. any) of 1.71, 95% confidence interval (1.16, 2.52). There were no further risk reductions with increasing activity levels. The association with breast cancer-specific mortality showed a similar dose-response but was far less pronounced with HR (none vs. any) = 1.22 (0.91, 1.64). In contrast, regarding cancer recurrence the dose-response was linear. However, this association was restricted to estrogen/progesterone receptor-negative (ER-/PR-) cases (p interaction = 0.033) with HR (highest vs. no recreational PA) = 0.53 (0.24, 1.16), p trend = 0.0045. Thus, breast cancer patients with a physically inactive lifestyle pre-diagnosis may decease prematurely irrespective of their cancer prognosis. Higher levels of exercise may reduce the risk of recurrence of ER-/PR- breast tumors.

Walking, bicycling, and sports in postmenopausal breast cancer survivors--results from a German patient cohort study

OBJECTIVES

Physical activity (PA) is increasingly discussed as a means to achieve both physical and psychological benefits for breast cancer patients and survivors. However, little is known about activity-specific PA behavior following diagnosis. Our objectives were to describe sports and active transportation in the course of breast cancer and to identify factors associated with these activities.

METHODS

We used data from a German cohort study including 1067 postmenopausal breast cancer survivors aged 50-75 years. Data were collected about walking and bicycling for transportation purposes and sports before diagnosis, during therapy, and 1 year after surgery. Associations between these activities and clinical, behavioral, and social characteristics were analyzed with logistic regression.

RESULTS

The proportions of physically active women decreased significantly during therapy compared with before diagnosis (walking: 75.1% vs. 89.7%; bicycling: 19.3% vs. 56.5%; sports: 14.8% vs. 64.5%; all p < 0.001). Calisthenics, swimming, and walking for exercise were the most frequent types of sport. Chemotherapy/radiotherapy was negatively associated with sports (odds ratio [OR]: 0.35 [0.17-0.73]) but positively associated with walking during therapy (OR: 2.08 [1.04-4.15]). Although sociodemographic factors showed weak associations with PA, participation in rehabilitation increased the likelihood for bicycling (OR: 1.48 [1.06-2.09]) and sports (OR: 1.88 [1.38-2.58]) 1 year after surgery.

CONCLUSIONS

The majority of women stopped exercising and bicycling during breast cancer therapy. Interventions promoting in particular moderate activities after breast cancer diagnosis are required for this population. Increasing participation in rehabilitation might help to increase the proportion of women who bicycle and engage in sports after breast cancer diagnosis.

[Physical activity and tumor diseases]

Physical activity is an important health measure for many diseases but in the past its role in cancer control has been understudied and underappreciated. This chapter updates a review of physical activity and cancer risk. Overall, the research to date suggests that physical activity reduces the risk of developing some forms of cancer, helps cancer survivors cope with and recover from treatment, improves the long-term health of cancer survivors and possibly even reduces the risk of recurrence and extends survival in some cancer survivor groups. Much research remains to be done in this field but the compelling data produced so far suggests that physical activity has an important effect on the development of cancer and precursor stages.

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.

[Risk and protective factors for breast cancer: a systematic review]

This review aimed to investigate risk and protective factors for breast cancer and to analyze whether scientific evidence from the World Cancer Research Fund and American Institute for Cancer Research, published in 2007, was confirmed by new research. In May 2010 we reviewed cohort and case-control analytical studies from 2007 to 2010 in the PubMed, LILACS, and SciELO databases. We selected 27 articles (14 case-control and 13 cohort studies). Breastfeeding and physical activity were protective factors against breast cancer, and alcohol consumption was a risk factor. A direct proportional relationship was observed between larger waist circumference, weight throughout adulthood, and height and risk of breast cancer in postmenopausal women. The association between body fat and breast cancer is contradictory in both premenopausal and postmenopausal women. According to the accumulated evidence, breastfeeding and healthy lifestyle are the factors most strongly associated with breast cancer prevention.

Body size, physical activity, and risk of triple-negative and estrogen receptor-positive breast cancer

BACKGROUND

Triple-negative breast cancer, characterized by a lack of hormone receptor and HER2 expression, is associated with a particularly poor prognosis. Focusing on potentially modifiable breast cancer risk factors, we examined the relationship between body size, physical activity, and triple-negative disease risk.

METHODS

Using data from 155,723 women enrolled in the Women's Health Initiative (median follow-up, 7.9 years), we assessed associations between baseline body mass index (BMI), BMI in earlier adulthood, waist and hip circumference, waist-hip ratio, recreational physical activity, and risk of triple-negative (n=307) and estrogen receptor-positive (ER+, n=2,610) breast cancers.

RESULTS

Women in the highest versus lowest BMI quartile had 1.35-fold (95% CI, 0.92-1.99) and 1.39-fold (95% CI, 1.22-1.58) increased risks of triple-negative and ER+ breast cancers, respectively. Waist and hip circumferences were positively associated with risk of ER+ breast cancer (Ptrend=0.01 for both measures) but were not associated with triple-negative breast cancer. Compared with women who reported no recreational physical activity, women in the highest activity tertile had similarly lower risks of triple-negative and ER+ breast cancers (HR=0.77; 95% CI, 0.51-1.13; and HR=0.85; 95% CI, 0.74-0.98, respectively).

CONCLUSIONS

Despite biological and clinical differences, triple-negative and ER+ breast cancers are similarly associated with BMI and recreational physical activity in postmenopausal women. The biological mechanisms underlying these similarities are uncertain and these modest associations require further investigation.

IMPACT

If confirmed, these results suggest potential ways postmenopausal women might modify their risk of both ER+ and triple-negative breast cancers.

Leisure-time physical activity and breast cancer risk defined by estrogen and progesterone receptor status--the Japan Public Health Center-based Prospective Study

OBJECTIVE

The study aims to investigate the association between leisure-time physical activity and breast cancer risk in consideration of tumor estrogen-receptor/progesterone-receptor status.

METHODS

We conducted a population-based prospective cohort study among 53,578 women in the Japan Public Health Center-based Prospective Study. Leisure-time physical activity was assessed by self-reported questionnaires. A Cox proportional hazards regression model was used to derive relative risks and 95% confidence intervals.

RESULTS

From 1990-1993 to the end of 2007, 652 cases were identified. The breast cancer rates (per 100,000 person-years) in the sedentary groups (≤3 days/month) was 84 in overall, 97 in premenopausal and 75 in postmenopausal women. We observed a statistically significant inverse association between leisure-time physical activity and breast cancer risk (relative risk(≥3 days/week vs. ≤3 days/month)=0.73; 95% confidence interval 0.54-1.00; p(trend) 0.037), particularly in estrogen receptor+progesterone receptor+ (relative risk 0.43; 0.19-1.00; p(trend) 0.022), and this inverse trend was apparent among postmenopausal women (relative risk 0.25; 0.06-1.06; p(trend) 0.041). An inverse trend was also observed between daily total physical activity and postmenopausal estrogen receptor+progesterone receptor+ risk (p=0.046). Among body mass index ≥25 kg/m(2) group, leisure-time physical activity was associated with decreased risk (relative risk(≥1 day/week vs. ≤3 days/month)=0.65; 0.43-0.97; p(trend) 0.033).

CONCLUSION

Active participation in leisure-time physical activity may contribute to a decrease in breast cancer risk, particularly for postmenopausal estrogen receptor+progesterone receptor+ tumors.

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.

Population attributable risk of invasive postmenopausal breast cancer and breast cancer subtypes for modifiable and non-modifiable risk factors

BACKGROUND

The population-level impact of modifiable postmenopausal breast cancer risk factors is incompletely understood, especially regarding potential heterogeneity by estrogen receptor (ER) and progesterone receptor (PR) status.

METHODS

Using data on 3074 cases and 6386 controls from a population-based case-control study of postmenopausal breast cancer conducted in Germany between 2002 and 2005, we calculated multivariable-adjusted odds ratios and population attributable risks (PARs) for modifiable and non-modifiable risk factors. We examined overall postmenopausal invasive breast cancer as well as tumor ER/PR subtypes. A bootstrap method provided estimates of 95% confidence intervals (95%CIs).

RESULTS

The summary PARs (95%CIs) for non-modifiable risk factors (age at menarche, age at menopause, parity, benign breast disease, and family history of breast cancer) were 37.2% (27.1-47.2%) regarding overall invasive tumors, 36.5% (23.3-47.6%) regarding ER+/PR+ tumors, 47.9% (26.4-64.4%) regarding ER+/PR- tumors, and 31.1% (4.0-51.9%) regarding ER-/PR- tumors. Of the modifiable risk factors (hormone therapy (HT) use, physical inactivity, BMI, alcohol consumption), HT use and physical inactivity had the highest impact with PARs of 19.4% (15.9-23.2%) and 12.8% (5.5-20.8%), respectively, regarding overall invasive tumors. For ER+/PR+ tumors, the corresponding PARs were 25.3% (20.9-29.7%) and 16.6% (7.0-26.0%). The summary PARs (95%CIs) for HT use and physical inactivity together were 29.8% (21.8-36.9%) and 37.9% (30.6-46.2%) regarding overall invasive and ER+/PR+ tumors, respectively.

CONCLUSIONS

The population-level impact of modifiable risk factors appears to be comparable to that of non-modifiable risk factors. Alterations in HT use and physical inactivity could potentially reduce postmenopausal invasive breast cancer incidence in Germany by nearly 30%, with the largest potential for reduction among ER+/PR+ tumors, the most frequently diagnosed subtype.

Trends in the incidence of cancer in the Sousse region, Tunisia, 1993-2006

In this article, we analyzed trends in incidence rates of the major cancer sites for a 14-year period, 1993-2006, in the Sousse region localized in the centre of Tunisia. Five-year age-specific rates, crude incidence rates (CR), world age-standardized rates (ASR), percent change (PC) and annual percent change (APC) were calculated using annual data on population size and its estimated age structure. A total of 6,975 incident cases of cancer were registered, with a male to-female sex ratio of 1.4:1. ASRs showed stable trends (-0.1% in males, and +1.0% in females). The leading cancer sites in rank were lung, breast, lymphoma, colon-rectum, bladder, prostate, leukemia, stomach and cervix uteri. For males, the incidence rates of lung, bladder and prostate cancers remained stable over time. While, cancers of colon-rectum showed a marked increase in incidence (APC: +4.8%; 95% CI: 1.2%, 8.4%) and non-Hodgkin's lymphoma (NHL) showed a notable decline (APC: -4.4%; 95% CI: -8.2, -0.6). For females, cancers of the breast (APC: +2.2%; 95% CI: 0.4%, 4.0%) and corpus uteri (APC: +7.4%; 95% CI: 2.8%, 12.0%) showed a marked increase in incidence during the study period, while the cervix uteri cancer decreased significantly (APC: -6.1%; 95% CI: -9.2%, -3.0%). The results underline the increasing importance of cancer as a cause of mortality and morbidity in Tunisia. Our findings justify the need to develop effective program aiming at the control and prevention of the spread of cancer amongst Tunisian population.

Determinants of sports, cycling, walking and overall leisure-time physical activity among postmenopausal women in Germany

OBJECTIVE

Convincing evidence exists for a beneficial effect of physical activity (PA) on health and well-being for elderly women. Nevertheless, many women in Germany are insufficiently physically active. Activity promotion programmes should target women in particular need. Thus, we examined subject-related determinants of PA for postmenopausal women in Germany.

DESIGN

Associations of sociodemographic, anthropometric, lifestyle and health-related factors with activity since the age of 50 years were assessed with multiple linear and logistic regression models, regarding overall leisure-time PA (LPA) in metabolic equivalent hours per week, engagement in sports (ever v. never), cycling (yes v. no) and walking (≥3·5 v. <3·5 h/week).

SETTING

All controls from a population-based case-control study carried out in 2002-2005 in Germany (MARIE study).

SUBJECTS

A total of 6569 postmenopausal women.

RESULTS

We found significant associations of overall LPA, sports, cycling and walking in postmenopausal years with several characteristics, among others: obese v. normal BMI (adjusted OR: ORsports = 0·73; ORcycling = 0·60; ORwalking = 0·63), tall v. short (ORsports = 1·49), worker v. medium employee (ORsports = 0·47), working full time v. unemployed/retired (ORsports = 0·80; ORwalking = 0·56), current v. non-smoker (ORsports = 0·62; ORcycling = 0·62; ORwalking = 0·82), non-German nationality (ORsports = 0·58; ORcycling = 0·41). Parity seemed more relevant than marital status for sports or cycling activity. Further, CVD, hypertension and diabetes were significantly associated with lower activity (ORsports = 0·77, 0·79 and 0·80; ORcycling = 0·80, 0·75 and 0·85, respectively).

CONCLUSIONS

Our results suggest potential target groups for promoting sports, cycling or walking activity. Postmenopausal women with chronic diseases may need to be stronger encouraged by their physicians to engage in adequate PA for the management of their diseases.

The use of herbal preparations to alleviate climacteric disorders and risk of postmenopausal breast cancer in a German case-control study

BACKGROUND

The use of herbal preparations (HEP) to alleviate climacteric disorders is expected to increase as women seek alternatives to menopausal hormone therapy to avoid the associated breast cancer risk. Data are sparse on the long-term effects of HEP containing phytoestrogens and black cohosh on breast cancer risk.

METHODS

Within a German case-control study, associations between patterns of HEP use and incident breast cancer were investigated in 10,121 postmenopausal women (3,464 cases, 6,657 controls). Information on HEP use was collected in face-to-face interviews supported by a list of brand names. Multivariate logistic and polytomous regression analyses were done.

FINDINGS

Ever use of HEP (9.9%) was inversely associated with invasive breast cancer [odds ratio (OR), 0.74; 95% confidence interval (CI), 0.63-0.87] in a dose-dependent manner (OR, 0.96 per year of use; P = 0.03). Classes of HEP did not differ significantly (P(heterogeneity) = 0.81). Risks for invasive ductal (OR, 0.72; 95% CI, 0.60-0.87) and combined lobular/mixed/tubular tumors (OR, 0.76; 95% CI, 0.58-1.01) were similarly reduced by any HEP use but not for in situ carcinomas (1.34; 95% CI, 0.86-2.09). There were no substantial differences in associations of HEP use by estrogen receptor status (ER(+) OR, 0.74; 95% CI, 0.62-0.89; ER- OR, 0.68, 95% CI, 0.50-0.93) and progesterone receptor status of the tumor.

INTERPRETATION

Our findings support the hypothesis that HEP use protects from invasive breast cancer in postmenopausal women. Among conceivable modes of action, those independent of estrogen receptor-mediated pathways seem to be involved (i.e., cytotoxicity, apoptosis).

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.