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

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.

Background risk of breast cancer and the association between physical activity and mammographic density

INTRODUCTION

High physical activity has been shown to decrease the risk of breast cancer, potentially by a mechanism that also reduces mammographic density. We tested the hypothesis that the risk of developing breast cancer in the next 10 years according to the Tyrer-Cuzick prediction model influences the association between physical activity and mammographic density.

METHODS

We conducted a population-based cross-sectional study of 38,913 Swedish women aged 40-74 years. Physical activity was assessed using the validated web-questionnaire Active-Q and mammographic density was measured by the fully automated volumetric Volpara method. The 10-year risk of breast cancer was estimated using the Tyrer-Cuzick (TC) prediction model. Linear regression analyses were performed to assess the association between physical activity and volumetric mammographic density and the potential interaction with the TC breast cancer risk.

RESULTS

Overall, high physical activity was associated with lower absolute dense volume. As compared to women with the lowest total activity level (<40 metabolic equivalent hours [MET-h] per day), women with the highest total activity level (≥50 MET-h/day) had an estimated 3.4 cm(3) (95% confidence interval, 2.3-4.7) lower absolute dense volume. The inverse association was seen for any type of physical activity among women with <3.0% TC 10-year risk, but only for total and vigorous activities among women with 3.0-4.9% TC risk, and only for vigorous activity among women with ≥5.0% TC risk. The association between total activity and absolute dense volume was modified by the TC breast cancer risk (P interaction = 0.05). As anticipated, high physical activity was also associated with lower non-dense volume. No consistent association was found between physical activity and percent dense volume.

CONCLUSIONS

Our results suggest that physical activity may decrease breast cancer risk through reducing mammographic density, and that the physical activity needed to reduce mammographic density may depend on background risk of breast cancer.

Differences among college women for breast cancer prevention acquired information-seeking, desired apps and texts, and daughter-initiated information to mothers

The purpose of this study was to examine among college women acquired breast cancer prevention information-seeking, desired apps and texts, and information given to mothers. Using a cross-sectional study, a survey was administered to college women at a southwestern university. College women (n = 546) used the Internet (44 %) for active breast cancer prevention information-seeking and used the Internet (74 %), magazines (69 %), and television (59 %) for passive information receipt. Over half of the participants desired breast cancer prevention apps (54 %) and texts (51 %). Logistic regression analyses revealed predictors for interest to receive apps were ethnicity (Hispanic), lower self-efficacy, actively seeking online information, and older age and predictors for interest to receive texts were lower self-efficacy and higher university level. Eighteen percent of college women (n = 99) reported giving information to mothers and reported in an open-ended item the types of information given to mothers. Predictors for giving information to mothers were actively and passively seeking online information, breast self-exam practice, and higher university level. Screenings were the most frequent types of information given to mothers. Breast cancer prevention information using apps, texts, or Internet and daughter-initiated information for mothers should be considered in health promotion targeting college students or young women in communities. Future research is needed to examine the quality of apps, texts, and online information and cultural differences for breast cancer prevention sources.

Human subjects protection: an event monitoring committee for research studies of girls from breast cancer families

PURPOSE

Researchers must monitor the safety of research participants, particularly in studies involving children and adolescents. Yet, there is limited guidance for the development and implementation of oversight committees for psychosocial, behavioral intervention, and observational studies.

METHODS

We implemented a model for an Event Monitoring Committee (EMC) in three related studies recruiting 6- to 19-year-old girls from families with and without breast cancer.

RESULTS

The EMC model can be valuable for investigators and local institutional review boards when additional oversight is desired. Recommendations are provided and intended to be broadly applicable to a wide range of research activities designed to improve the health of children, adolescents, and families. EMC goals, membership, and procedures for monitoring and assessing risks and benefits should be defined but should also be flexible and tailored to the study design and population. The EMC model also provides an independent comprehensive, study-wide oversight mechanism for multicenter psychosocial, behavioral intervention, and observational studies.

CONCLUSIONS

An EMC provides an alternative oversight approach where additional independent assessment and oversight of study-related risks are desired, particularly in the setting of vulnerable populations, children and adolescents, or where risks nontraditional to the medical field (i.e., social, emotional, or cultural) are possible.

Adolescent physical activity and inactivity: a prospective study of risk of benign breast disease in young women

In previous investigations of adolescent activity recalled in adulthood, modest reductions in risk of benign breast disease (BBD) and premenopausal breast cancer were seen with moderate-strenuous activity during high school. We therefore investigated physical activity, walking, and recreational inactivity (watching TV-videos, playing computer-videogames) reported by adolescent girls in relation to their subsequent risk for BBD as young women. The Growing Up Today Study includes 9,039 females, 9-15 years at study initiation (1996), who completed questionnaires annually through 2001, then in 2003, 2005, 2007, 2010 and 2013. Annual surveys (1996-2001) obtained data on physical and sedentary activities during the past year. Beginning in 2005, women (≥18 years) reported whether they had ever been diagnosed with BBD confirmed by breast biopsy (n = 133 cases, to 11/01/2013). Logistic regression (adjusted for baseline adiposity and age; additional factors in multivariable-adjusted models) estimated associations between adolescent activities (moderate-vigorous, walking, METS, inactivity) and biopsy-confirmed BBD in young women. Girls who walked the most had significantly lower risk of BBD (multivariable-adjusted OR = 0.61, ≥30 vs ≤15 min/day; p = .049). We observed no evidence that inactivity (≥3 vs <2 h/day OR = 1.02, p = .92) or METS (top vs bottom tertile OR = 1.19, p = .42) were associated with BBD. Accounting for factors including family history, childhood adiposity, and other activities and inactivities, adolescent girls who walked the most were at lower risk for BBD. We found no evidence that high moderate-vigorous activity might reduce risk, nor did we observe any association with inactivity. Continued follow-up will re-evaluate these findings as more BBD cases, and ultimately breast cancer, are diagnosed.

BMI and Breast Cancer in Korean Women: A Meta-Analysis

INTRODUCTION

The number of breast cancer women has increased dramatically in Korea. The cause is perceived to stem from adaptation to a westernized life style which increases body mass index (BMI). However, there are no meta-analysis data available that could help in understanding the relationship between Korean females' BMI and breast cancer occurrence.

METHOD

All the published articles that investigated the relationship of Korean women's BMI with breast cancer prevalence between 1950 and 2007 were included in this study, based on a screen of the comput- erized databases that search for these articles (MEDLINE, RISS4U and KMBase). The commercial software Comprehensive Meta Analysis was used for the analysis.

RESULTS

The high BMI score group presented a higher prevalence of breast cancer on both a fixed-effects model [odds ratio (OR) = 1.282; 95% confidence interval (CI) = 1.209, 1.361] and a random-effects model (OR = 1.388; 95% CI = 1.129, 1.706). In addition, a high BMI score on pre- and postmenopausal groups was found to have a significantly higher prevalence of breast cancer on both a fixed-effects model (OR = 1.467; 95% CI = 1.268, 1.698, OR = 1.614; 95% CI = 1.360, 1.917, pre- and postmenopausal, respectively) and a random-effects model (OR = 1.387; 95% CI = 1.134, 1.696, OR = 1.681; 95% CI = 1.149, 2.461, pre- and postmenopausal, respectively).

CONCLUSION

This meta-analysis of Korean women showed that a high BMI was related to a higher inci- dence rate of breast cancer. This study used a subgroup analysis of pre- and postmenopausal groups; the high BMI subset in both the pre- and postmenopausal groups was shown to have a higher incidence rate of breast cancer. [Asian Nursing Research 2009;3(1):31-40].

Breast cancer risk accumulation starts early: prevention must also

Nearly one in four breast cancers is diagnosed before the age of 50, and many early-stage premalignant lesions are present but not yet diagnosed. Therefore, we review evidence to support the strategy that breast cancer prevention efforts must begin early in life. This study follows the literature review methods and format. Exposures during childhood and adolescence affect a woman's long-term risk of breast cancer, but have received far less research attention than exposures that occur later in life. Breast tissue undergoes rapid cellular proliferation between menarche and first full-term pregnancy, and risk accumulates rapidly until the terminal differentiation that accompanies first pregnancy. Evidence on childhood diet and growth in height, and adolescent alcohol intake, among other adolescent factors is related to breast cancer risk and risk of premalignant proliferative benign lesions. Breast cancer prevention efforts will have the greatest effect when initiated at an early age and continued over a lifetime. Gaps in knowledge are identified and deserve increase attention to inform prevention.

Priorities for the primary prevention of breast cancer

Despite recent calls to intensify the search for new risk factors for breast cancer, acting on information that we already have could prevent thousands of cases each year. This article reviews breast cancer primary prevention strategies that are applicable to all women, discusses the underutilization of chemoprevention in high-risk women, highlights the additional advances that could be made by including young women in prevention efforts, and comments on how the molecular heterogeneity of breast cancer affects prevention research and strategies.

Adolescent dietary fiber, vegetable fat, vegetable protein, and nut intakes and breast cancer risk

The importance of early-life exposures in breast cancer development is increasingly recognized. However, limited research has evaluated the relationship between adolescent diet and subsequent risk of breast cancer and reported inconsistent results. This population-based case-control study investigated the associations of dietary fiber, vegetable protein, vegetable fat, and nuts consumed during adolescence with adult breast cancer risk. Women, ages 25-74 years, who were diagnosed with first primary breast cancer between 2002 and 2003, were identified using the Ontario Cancer Registry. Controls were identified through random-digit dialing and age-frequency matched to cases. Diet at ages 10-15 was assessed with a 55-item food frequency questionnaire among 2,865 cases and 3,299 controls. Logistic regression was performed to estimate odds ratios (ORs) and 95 % confidence intervals (CIs). Inverse associations were found between intakes of dietary fiber, vegetable protein, vegetable fat, and nuts during adolescence and breast cancer risk, which persisted after controlling for adult intakes. The ORs (95 % CI) for the highest versus the lowest quintile of intake were 0.66 (0.55-0.78; P trend < 0.0001) for fiber, 0.80 (0.68-0.95; P trend = 0.01) for vegetable protein, 0.74 (0.63-0.87; P trend = 0.002) for vegetable fat, and 0.76 (0.61-0.95 for ≥1 serving/day vs. <1 serving/month intake; P trend = 0.04) for nuts. The reduced risk for adolescent intakes of fiber, vegetable protein, and nuts was largely limited to postmenopausal women (P interaction ≤ 0.05). Dietary fiber, vegetable protein, vegetable fat, and nuts consumed during adolescence were associated with reduced breast cancer risk.

Adolescent dietary fiber, vegetable fat, vegetable protein, and nut intakes and breast cancer risk

The importance of early-life exposures in breast cancer development is increasingly recognized. However, limited research has evaluated the relationship between adolescent diet and subsequent risk of breast cancer and reported inconsistent results. This population-based case-control study investigated the associations of dietary fiber, vegetable protein, vegetable fat, and nuts consumed during adolescence with adult breast cancer risk. Women, ages 25-74 years, who were diagnosed with first primary breast cancer between 2002 and 2003, were identified using the Ontario Cancer Registry. Controls were identified through random-digit dialing and age-frequency matched to cases. Diet at ages 10-15 was assessed with a 55-item food frequency questionnaire among 2,865 cases and 3,299 controls. Logistic regression was performed to estimate odds ratios (ORs) and 95 % confidence intervals (CIs). Inverse associations were found between intakes of dietary fiber, vegetable protein, vegetable fat, and nuts during adolescence and breast cancer risk, which persisted after controlling for adult intakes. The ORs (95 % CI) for the highest versus the lowest quintile of intake were 0.66 (0.55-0.78; P trend < 0.0001) for fiber, 0.80 (0.68-0.95; P trend = 0.01) for vegetable protein, 0.74 (0.63-0.87; P trend = 0.002) for vegetable fat, and 0.76 (0.61-0.95 for ≥1 serving/day vs. <1 serving/month intake; P trend = 0.04) for nuts. The reduced risk for adolescent intakes of fiber, vegetable protein, and nuts was largely limited to postmenopausal women (P interaction ≤ 0.05). Dietary fiber, vegetable protein, vegetable fat, and nuts consumed during adolescence were associated with reduced breast cancer risk.

Adolescent physical activity in relation to breast cancer risk

Adolescent physical activity may protect against premenopausal breast cancer. Whether it also prevents postmenopausal breast cancer, and whether associations are independent of adult activity, is unclear. We evaluated this association among 75,669 women in the Nurses' Health Study II. In 1997, participants reported strenuous, moderate, and walking activity (hours/week) at ages 12-13, 14-17, 18-22, and 23-29 years. We estimated metabolic equivalent task hours (MET-h)/week. Participants also reported current physical activity over follow-up. Breast cancer diagnoses (n = 2,697; premenopausal = 1,351; postmenopausal = 965) through 2011 were reported by participants and confirmed with medical records. We additionally stratified analyses by median age at diagnosis. In Cox proportional hazards models adjusted for adolescent characteristics, physical activity from ages 14-22 was modestly inversely associated with premenopausal breast cancer [e.g., hazard ratio (HR) comparing 72+ to <21 MET-h/week 0.81 (95 % confidence interval (CI) 0.69-0.95; p-trend = 0.10) for ages 14-17 and 0.85 (95 % CI 0.71-1.02; p-trend = 0.06 for ages 18-22]. However, adjustment for adult activity and additional breast cancer risk factors attenuated the associations [ages 14-17: 0.85 (95 % CI 0.73-1.00; p-trend = 0.33)]. Associations were stronger among women diagnosed at younger ages [e.g., ages 18-22, HR 0.77 (95 % CI 0.60-0.99; p-trend = 0.05) for women diagnosed before 46.9 years; HR 1.02 (95 % CI 0.79-1.32; p-trend = 0.94) for those diagnosed at/after 46.9 years]. Early life physical activity was not associated with postmenopausal breast cancer. Overall, adolescent physical activity was not associated with breast cancer risk. However, we observed a suggestive inverse association of physical activity at ages 14-22 years with premenopausal breast cancer.

Carpe Diem: time to seize the opportunity for cancer prevention

In his plea for increased resources to implement cancer prevention strategies, Graham Colditz, MD, states that half or more of cancers in the U.S. and other high-income countries are preventable with information already available. He describes the data-driven possibilites: screening, vaccination, exercise, smoking cessation, sun protection, safe sexual practices, and moderate to no alcohol intake, as well as approaches to implement these strategies and makes a compelling case for using resources for this purpose. Dr. Colditz is Associate Director of Prevention and Control in the Alvin J. Siteman Cancer Center, and Niess-Gain Professor in the Department of Surgery at the Washington University School of Medicine. He received his PhD in epidemiology from Harvard University, and his Internal Medicine Training at the Royal Brisbane Hospital in Australia. Dr. Colditz has an enormous volume of publications, with over 800 original research articles. He has worked to identify lifestyle and environmental factors that affect people's health, and to develop and teach cancer prevention strategies at the individual and community levels. His research also powers a website-www.yourdiseaserisk.wustl.edu-that helps people assess their risk of developing cancer, diabetes and other diseases as well as suggesting ways to lead longer, healthier lives. His work is inspirational in combining excellent scientific investigation with dedication to making results available and useful to non-scientists. Gini F. Fleming, MD, Cancer Education Committee Chair.

Body mass index, waist circumference, physical activity, and risk of hearing loss in women

BACKGROUND

Acquired hearing loss is highly prevalent, but prospective data on potentially modifiable risk factors are limited. In cross-sectional studies, higher body mass index (BMI), larger waist circumference, and lower physical activity have been associated with poorer hearing, but these have not been examined prospectively.

METHODS

We examined the independent associations between BMI, waist circumference, and physical activity, and self-reported hearing loss in 68,421 women in the Nurses' Health Study II from 1989 to 2009. Baseline and updated information on BMI, waist circumference, and physical activity was obtained from biennial questionnaires.

RESULTS

After more than 1.1 million person-years of follow-up, 11,286 cases of hearing loss were reported to have occurred. Higher BMI and larger waist circumference were associated with increased risk of hearing loss. Compared with women with BMI <25 kg/m(2), the multivariate-adjusted relative risk (RR) for women with BMI ≥ 40 was 1.25 (95% confidence interval [CI], 1.14-1.37). Compared with women with waist circumference <71 cm, the multivariate-adjusted RR for waist circumference >88 cm was 1.27 (95% CI, 1.17-1.38). Higher physical activity was related inversely to risk; compared with women in the lowest quintile of physical activity, the multivariate-adjusted RR for women in the highest quintile was 0.83 (95% CI, 0.78-0.88). Walking 2 hours per week or more was associated inversely with risk. Simultaneous adjustment for BMI, waist circumference, and physical activity slightly attenuated the associations but they remained statistically significant.

CONCLUSIONS

Higher BMI and larger waist circumference are associated with increased risk, and higher physical activity is associated with reduced risk of hearing loss in women. These findings provide evidence that maintaining healthy weight and staying physically active, potentially modifiable lifestyle factors, may help reduce the risk of hearing loss.

The effect of physical activity across the menstrual cycle on reproductive function

PURPOSE

To evaluate the association between physical activity (PA) across the menstrual cycle and reproductive function.

METHODS

The BioCycle Study (2005-2007) followed 259 healthy premenopausal women not using hormonal contraceptives for up to two menstrual cycles (N = 509 cycles). Serum leptin, estradiol, progesterone, luteinizing hormone, follicle-stimulating hormone, and testosterone were measured five to eight times per cycle. Linear mixed models were used to estimate the effect of past-week PA (measured four times during each cycle) on hormone levels. Past-week PA was categorized into tertiles based on metabolic equivalent of task hours per week (cut-points were 15.3 and 35.7). Risk ratios for sporadic anovulation were estimated using generalized linear models. Analyses adjusted for habitual PA (assessed at baseline), body mass index, race, age, and perceived stress. Linear mixed models used inverse probability weights to control for concurrent reproductive hormones and caloric intake.

RESULTS

High past-week PA was inversely associated with leptin (-6.6%; 95% confidence interval, -10.6 to -2.5) and luteal phase progesterone (-22.1%; -36.2 to -4.7) as compared with low past-week PA. High past-week PA was not significantly associated with sporadic anovulation (adjusted risk ratio, 1.5; 0.6 to 3.4).

CONCLUSIONS

High levels of PA were modestly associated with changes in select hormones but not sporadic anovulation among moderate to highly active premenopausal women.

Increased plasma levels of soluble vascular endothelial growth factor receptor 1 (sFlt-1) in women by moderate exercise and increased plasma levels of vascular endothelial growth factor in overweight/obese women

The incidence of breast cancer is increasing worldwide, and this seems to be related to an increase in lifestyle risk factors, including physical inactivity and overweight/obesity. We have reported previously that exercise induced a circulating angiostatic phenotype characterized by increased soluble fms-like tyrosine kinase-1 (sFlt-1) and endostatin and decreased unbound vascular endothelial growth factor (VEGF) in men. However, there are no data on women. The present study determines the following: (a) whether moderate exercise increased sFlt-1 and endostatin and decreased unbound VEGF in the circulation of adult female volunteers and (b) whether overweight/obese women have a higher plasma level of unbound VEGF than lean women. A total of 72 African American and White adult women volunteers ranging in age from 18 to 44 years were enrolled in the exercise study. All the participants walked on a treadmill for 30 min at a moderate intensity (55-59% heart rate reserve), and oxygen consumption (VO(2)) was quantified utilizing a metabolic cart. We obtained blood samples before and immediately after exercise from 63 participants. ELISA assays showed that the plasma levels of sFlt-1 were 67.8±3.7 pg/ml immediately after exercise (30 min), significantly higher than the basal levels, 54.5±3.3 pg/ml, before exercise (P<0.01; n=63). There was no significant difference in the % increase in the sFlt-1 levels after exercise between African American and White (P=0.533) women or between lean and overweight/obese women (P=0.892). There was no significant difference in the plasma levels of unbound VEGF (35.28±5.47 vs. 35.23±4.96 pg/ml; P=0.99) or endostatin (111.12±5.48 vs. 115.45±7.15 ng/ml; P=0.63) before and after exercise. The basal plasma levels of unbound VEGF in overweight/obese women were 52.26±9.6 pg/ml, significantly higher than the basal levels of unbound VEGF in lean women, 27.34±4.99 pg/ml (P<0.05). The results support our hypothesis that exercise-induced plasma levels of sFlt-1 could be an important clinical biomarker to explore the mechanisms of exercise training in reducing the progression of breast cancer and that VEGF is an important biomarker in obesity and obesity-related cancer progression.

Epidemiology and prognosis of breast cancer in young women

Breast cancer is the most common malignancy in women with 6.6% of cases diagnosed in young women below the age of 40. Despite variances in risk factors, Age Standardized Incidence Rates of breast cancer in young women vary little between different countries. Review of modifiable risk factors shows that long-term use of oral contraceptives, low body mass index (BMI) and high animal fat diet consumption are associated with increased risk of premenopausal breast cancer. Decreased physical activity and obesity increase risks of breast cancer in postmenopausal women, but data on premenopausal women rather shows that high BMI is associated with decreased risk of breast cancer. Non-modifiable risk factors such as family history and genetic mutations do account for increased risks of breast cancer in premenopausal women. Breast cancer in young women is associated with adverse pathological factors, including high grade tumors, hormone receptor negativity, and HER2 overexpression. This has a significant negative impact on the rate of local recurrence and overall survival. Moreover, younger women often tend to present with breast cancer at a later stage than their older counterparts, which further explains worse outcome. Despite these factors, age per se is still being advocated as an independent role player in the prognosis. This entails more aggressive treatment modalities and the need for closer monitoring and follow-up.

Genetic polymorphisms of CYP2E1, GST, and NAT2 enzymes are not associated with risk of breast cancer in a sample of Lebanese women

Changes in the activity of drug metabolizing enzymes (DMEs) are potentially associated with cancer risk. This relationship is attributed to their involvement in the bioactivation of multiple procarcinogens or the metabolism of multiple substrates including an array of xenobiotics and environmental carcinogens. 326 Lebanese women of whom 99 were cancer free (controls) and 227 were diagnosed with breast cancer (cases) were included. Blood for DNA was collected and medical charts were reviewed. Three genotyping methods were employed including: (1) restriction fragment length polymorphism (RFLP) for CYP2E1*5B, CYP2E1*6, NAT2*5 and NAT2*6; (2) gel electrophoresis for GSTM1 and GSTT1; and (3) real-time PCR for GSTP1 Ile/Val polymorphism. We analyzed the relationship between genetic susceptibilities in selected xenobiotic metabolizing genes and breast cancer risk. Allele frequencies were fairly similar to previously reported values from neighboring populations with relevant migration routes. There were no statistically significant differences in the distribution of variant carcinogen metabolizing genes between cases and controls even after adjusting for age at diagnosis, menopausal status, smoking, and alcohol intake. Despite its limitations, this is the first study that assesses the role of genetic polymorphisms in DMEs with breast cancer in a sample of Lebanese women. Further studies are needed to determine the genetic predisposition and gene-environment interactions of breast cancer in this population.

Intensity of recreational physical activity in different life periods in relation to breast cancer among women in the region of Western Pomerania

Background

Recreational physical activity has been consistently associated with lower breast cancer risk, but there is a need to study the intensity and duration of activity that are critical to reduce the risk. The aim of this study was to examine the influence of moderate and vigorous intensity of recreational physical activity performed at different age periods on breast cancer risk.

Material and methods

The case-control study included 858 women with histological confirmation of invasive breast cancer and 1085 women free of any cancer diagnosis, residents of the region of Western Pomerania, aged 28–79 years. The frequency, duration and intensity of lifetime household, occupational and recreational physical activity, sociodemographic characteristics, reproductive factors, family history of breast cancer, current weight and height, and lifestyle habits were measured using a self-administered questionnaire. Unconditional logistic regression analyses were applied to estimate odds ratios (ORs) and 95% confidence intervals (CIs). The risk estimates were controlled for potential risk factors and lifetime household and occupational activities.

Results

We found a risk reduction for recreational activity done early in life (age periods 14–20, 21–34, 35–50 years), particularly at ages 14–20 and 21–34 years, regardless of intensity. Active women engaging in more than 4.5 hours per week of moderate activity during ages 14–20 years had, on average, a 36% lower risk (OR = 0.64, 95% CI: 0.45–0.89) than women who were never or rarely active. For the women who reported 4.5 hours per week of vigorous activity during this period we found about 64% risk reduction (OR = 0.36, 95% CI: 0.26–0.51). For the period after 50 years of age, recreational activity of moderate or vigorous intensity was not significantly associated with the risk.

Conclusions

Recreational physical activity of moderate or vigorous intensity done during adolescence, early and middle adulthood, particularly at ages 14–20 and 21–34 years, is associated with significantly decreased breast cancer risk.

Physical activity and risk of breast cancer: a meta-analysis of prospective studies

We conducted a meta-analysis to summarize the evidence from prospective studies regarding the association between physical activity and breast cancer risk. A comprehensive search was conducted to identify eligible studies. The fixed or random effect model was used based on heterogeneity test. The dose-response relationship was assessed by restricted cubic spline model and multivariate random-effect meta-regression. Overall, 31 studies with 63,786 cases were included, and the combined relative risk (RR) with 95 % CI of breast cancer was 0.88 (0.85-0.91). In subgroup analysis by activity type, data from 27 studies including 37,568 cases for non-occupational activity (including recreational activity and household activity) and seven studies including 28,268 cases for occupational activity were used, and the RR (95 % CI) of breast cancer was 0.87 (0.83-0.91) and 0.90 (0.83-0.97), respectively. The inverse association was consistent among all subgroups analyses. Stronger association was found for subjects with BMI <25 kg/m(2) [0.72 (0.65-0.81)], premenopausal women [0.77 (0.72-0.84)], and estrogen and progesterone receptor-negative breast cancer [0.80 (0.73-0.87)]. Dose-response analysis suggested that the risk of breast cancer decreased by 2 % (P < 0.00) for every 25 metabolic equivalent (MET)-h/week increment in non-occupational physical activity, 3 % (P < 0.00) for every 10 MET-h/week (roughly equivalent to 4 h/week of walking in 2 miles/h or 1 h/week of running in 6 miles/h) increment in recreational activity, and 5 % (P < 0.00) for every 2 h/week increment in moderate plus vigorous recreational activity, respectively. Physical activity could significantly reduce the risk of breast cancer.

Knowledge and perceptions of familial and genetic risks for breast cancer risk in adolescent girls

Evidence suggests early events might modify adult breast cancer risk and many adolescents learn of familial and genetic risks for breast cancer. Little is known about how adolescent girls understand and respond to breast cancer risk. Semi-structured interviews with 11-19 year-old girls at high-risk and population-risk for breast cancer evaluated knowledge and perceptions of breast cancer risk and risk modification. Framework analysis and descriptive statistics were utilized to analyze open-ended responses. Risk group and age differences were evaluated by Fisher's exact and McNemar's tests. Fifty-four girls (86 % of invited), 35 high-risk (65 %), and 19 population-risk (35 %) completed interviews. The most frequently reported risk for breast cancer was family history/hereditary predisposition (66 %). Only 17 % of girls were aware of BRCA1/2 genes. The majority (76 %) of high-risk girls perceive themselves to be at increased risk for breast cancer, compared to 22 % of population-risk girls (p = 0.001). Half of girls reported that women can get breast cancer before 20-years-old. The majority believe there are things women (70 %) and girls (67 %) can do to prevent breast cancer. Mother was the most frequently reported source of information for breast cancer among both high-risk (97 %) and population-risk (89 %) girls. In this study, many high-risk girls perceive themselves to be at increased risk for breast cancer, and many girls believe that breast cancer can occur in teens. Yet, most girls believe there are things women and girls can do to prevent breast cancer. Research evaluating the impact of awareness and perceptions of breast cancer risk on psychosocial, health, and risk behaviors is needed to develop strategies to optimize responses to cancer risk.

Objective habitual physical activity and estradiol levels in obese Latina adolescents

BACKGROUND

Lifetime physical activity (PA) is associated with decreased breast cancer (BC) risk; reports suggest that PA during adolescence contributes strongly to this relationship. PA lowers production of sex hormones, specifically estradiol, or decreases insulin resistance (IR), thereby lowering risk. Overweight Latina adolescents are insulin resistant and exhibit low levels of PA, potentially increasing their future BC risk.

METHODS

37 obese Latina adolescents (15.7 ± 1.1 yrs) provided measures of PA using accelerometry; plasma follicular phase estradiol, sex-hormone binding globulin, total and free testosterone, dehydroepiandrosterone-sulfate (DHEAS); IR using HOMA-IR; and body composition via DEXA. Partial correlations and stepwise linear regressions assessed cross-sectional relationships between sex hormones, IR and PA. Body composition, and age were included a priori as covariates.

RESULTS

Estradiol was negatively associated with accelerometer counts per minute (CPM; r = -0.4; P = .02), percent time spent in moderate PA (%MPA; r = -0.5; P = .006), and percent time in moderate or vigorous PA (%MVPA; r = -0.5; P = .007). DHEAS was positively associated with CPM (r = .4, P = .009), %MPA (r = .3, P = .04), and %MVPA (r = .3, P = .04). Other sex hormones and IR were not associated with PA measures.

CONCLUSION

This study is the first to show that higher habitual PA was inversely associated with estradiol in obese adolescents.

Association between physical activity and urinary estrogens and estrogen metabolites in premenopausal women

OBJECTIVE

The objective of the study was to evaluate in premenopausal women the relationships of physically active and sedentary behaviors reported for adulthood and adolescence with a comprehensive profile of estrogen metabolism.

METHODOLOGY

Fifteen estrogens and estrogen metabolites (jointly termed EM) were measured using liquid chromatography-tandem mass spectrometry in luteal phase urines from 603 premenopausal women in the Nurses' Health Study II. Geometric means of individual EM, metabolic pathway groups, and pathway ratios were examined by level of exposure after adjustment for age, body mass index, alcohol intake, menstrual cycle length, and sample collection timing.

RESULTS

High overall physical activity in adulthood (42+ metabolic equivalent h/wk vs. <3 metabolic equivalent h/wk) was associated with a 15% lower level of urinary estradiol (Ptrend=0.03) and 15% lower level of 16-hydroxylation pathway EM (Ptrend=0.03). Levels of 2- and 4-hydroxylation pathway EM did not differ significantly by physical activity. High overall activity was also positively associated with four ratios: 2-pathway EM to parent estrogens (Ptrend=0.05), 2-pathway catechols to parent estrogens (Ptrend=0.03), 2-pathway catechols to methylated 2-pathway catechols (Ptrend<0.01), and 2-hydroxyestrone to 16α-hydroxyestrone (Ptrend=0.01). Similar patterns of association were noted for walking and vigorous physical activity, but there was little evidence of associations with sedentary behaviors or activity during adolescence.

CONCLUSIONS

High levels of physical activity were associated with lower levels of parent estrogens and 16-hydroxylation pathway EM and preferential metabolism to 2-pathway catechols. The results of our analysis, the largest, most comprehensive examination of physical activity and estrogen metabolism to date, may be useful in future studies investigating the etiology of diseases linked to both physical activity and endogenous estrogen.

Applying what we know to accelerate cancer prevention

More than half of the cancer occurring today is preventable by applying knowledge that we already have. Tobacco, obesity, and physical inactivity are the modifiable causes of cancer that generate the most disease. Cancer burden can be reduced by alterations in individual and population behaviors and by public health efforts as long as these changes are driven by sound scientific knowledge and social commitment to change. The obstacles to these efforts are societal and arise from the organization of institutions, including academia, and in the habits of daily life. To achieve maximal possible cancer prevention, we will need better ways to implement what we know and improved infrastructure that will better incentivize and support transdisciplinary, multilevel research and successful intervention.

Risk factors for breast cancer for women aged 40 to 49 years: a systematic review and meta-analysis

BACKGROUND

Identifying risk factors for breast cancer specific to women in their 40s could inform screening decisions.

PURPOSE

To determine what factors increase risk for breast cancer in women aged 40 to 49 years and the magnitude of risk for each factor.

DATA SOURCES

MEDLINE (January 1996 to the second week of November 2011), Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Reviews (fourth quarter of 2011), Scopus, reference lists of published studies, and the Breast Cancer Surveillance Consortium.

STUDY SELECTION

English-language studies and systematic reviews of risk factors for breast cancer in women aged 40 to 49 years. Additional inclusion criteria were applied for each risk factor.

DATA EXTRACTION

Data on participants, study design, analysis, follow-up, and outcomes were abstracted. Study quality was rated by using established criteria, and only studies rated as good or fair were included. Results were summarized by using meta-analysis when sufficient studies were available or from the best evidence based on study quality, size, and applicability when meta-analysis was not possible. Data from the Breast Cancer Surveillance Consortium were analyzed with proportional hazards models by using partly conditional Cox regression. Reference groups for comparisons were set at U.S. population means.

DATA SYNTHESIS

Sixty-six studies provided data for estimates. Extremely dense breasts on mammography or first-degree relatives with breast cancer were associated with at least a 2-fold increase in risk for breast cancer. Prior breast biopsy, second-degree relatives with breast cancer, or heterogeneously dense breasts were associated with a 1.5- to 2.0-fold increased risk; current use of oral contraceptives, nulliparity, and age 30 years or older at first birth were associated with a 1.0- to 1.5-fold increased risk.

LIMITATIONS

Studies varied by measures, reference groups, and adjustment for confounders, which could bias combined estimates. Effects of multiple risk factors were not considered.

CONCLUSION

Extremely dense breasts and first-degree relatives with breast cancer were each associated with at least a 2-fold increase in risk for breast cancer in women aged 40 to 49 years. Identification of these risk factors may be useful for personalized mammography screening.

PRIMARY FUNDING SOURCE

National Cancer Institute.

Risk factors for breast cancer for women aged 40 to 49 years: a systematic review and meta-analysis

BACKGROUND

Identifying risk factors for breast cancer specific to women in their 40s could inform screening decisions.

PURPOSE

To determine what factors increase risk for breast cancer in women aged 40 to 49 years and the magnitude of risk for each factor.

DATA SOURCES

MEDLINE (January 1996 to the second week of November 2011), Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Reviews (fourth quarter of 2011), Scopus, reference lists of published studies, and the Breast Cancer Surveillance Consortium.

STUDY SELECTION

English-language studies and systematic reviews of risk factors for breast cancer in women aged 40 to 49 years. Additional inclusion criteria were applied for each risk factor.

DATA EXTRACTION

Data on participants, study design, analysis, follow-up, and outcomes were abstracted. Study quality was rated by using established criteria, and only studies rated as good or fair were included. Results were summarized by using meta-analysis when sufficient studies were available or from the best evidence based on study quality, size, and applicability when meta-analysis was not possible. Data from the Breast Cancer Surveillance Consortium were analyzed with proportional hazards models by using partly conditional Cox regression. Reference groups for comparisons were set at U.S. population means.

DATA SYNTHESIS

Sixty-six studies provided data for estimates. Extremely dense breasts on mammography or first-degree relatives with breast cancer were associated with at least a 2-fold increase in risk for breast cancer. Prior breast biopsy, second-degree relatives with breast cancer, or heterogeneously dense breasts were associated with a 1.5- to 2.0-fold increased risk; current use of oral contraceptives, nulliparity, and age 30 years or older at first birth were associated with a 1.0- to 1.5-fold increased risk.

LIMITATIONS

Studies varied by measures, reference groups, and adjustment for confounders, which could bias combined estimates. Effects of multiple risk factors were not considered.

CONCLUSION

Extremely dense breasts and first-degree relatives with breast cancer were each associated with at least a 2-fold increase in risk for breast cancer in women aged 40 to 49 years. Identification of these risk factors may be useful for personalized mammography screening.

PRIMARY FUNDING SOURCE

National Cancer Institute.

Commentary: eight ways to prevent cancer: a framework for effective prevention messages for the public

Research over the past 40 years has convincingly shown that lifestyle factors play a huge role in cancer incidence and mortality. The public, though, can often discount the preventability of cancer. That health information on the Internet is a vast and often scientifically suspect commodity makes promoting important and sound cancer prevention messages to the public even more difficult. To help address these issues and improve the public's knowledge of, and attitudes toward, cancer prevention, there need to be concerted efforts to create evidence-based, user-friendly information about behaviors that could greatly reduce overall cancer risk. Toward this end, we condensed the current scientific evidence on the topic into eight key behaviors. While not an end in themselves, "Eight Ways to Stay Healthy and Prevent Cancer" forms an evidence-based and targeted framework that supports broader cancer prevention efforts.

Exercise lowers estrogen and progesterone levels in premenopausal women at high risk of breast cancer

Experimental and clinical data support a role for estrogens in the development and growth of breast cancer, and lowered estrogen exposure reduces breast cancer recurrence and new diagnoses in high-risk women. There is varied evidence that increased physical activity is associated with breast cancer risk reduction in both pre- and postmenopausal women, perhaps via lowered estrogen levels. The purpose of this study was to assess whether exercise intervention in premenopausal women at increased breast cancer risk reduces estrogen or progesterone levels. Seven healthy premenopausal women at high risk for breast cancer completed a seven-menstrual-cycle study. The study began with two preintervention cycles of baseline measurement of hormone levels via daily first-morning urine collection, allowing calculation of average area under the curve (AUC) hormone exposure across the menstrual cycle. Participants then began five cycles of exercise training to a maintenance level of 300 min per week at 80-85% of maximal aerobic capacity. During the last two exercise cycles, urinary estradiol and progesterone levels were again measured daily. Total estrogen exposure declined by 18.9% and total progesterone exposure by 23.7%. The declines were mostly due to decreased luteal phase levels, although menstrual cycle and luteal phase lengths were unchanged. The study demonstrated the feasibility of daily urine samples and AUC measurement to assess hormone exposure in experimental studies of the impact of interventions on ovarian hormones. The results suggest value in exercise interventions to reduce hormone levels in high-risk women with few side effects and the potential for incremental benefits to surgical or pharmacologic interventions.

Lifetime physical activity and the incidence of proliferative benign breast disease

BACKGROUND

Exercise is a modifiable factor that is inversely related to risk for breast cancer. To determine if physical activity has a preventative effect on development of premalignant breast lesions, we examined the association between exercise and the incidence of proliferative benign breast disease.

METHODS

In 1997, the Nurses' Health Study II cohort reported levels of physical activity during adolescence and adulthood using a validated recall instrument. We followed 40,318 participants free from benign breast disease (BBD) or cancer prospectively for four years and confirmed 232 proliferative benign breast lesions by centralized pathology review. Cox proportional hazards models estimated the age-adjusted and multivariable-adjusted relative risks for physical activity and proliferative benign breast disease.

RESULTS

We observed a significant inverse association for walking and incidence of BBD, risk was reduced by 9% per hour of walking (95% CI 0% to 17%), (p trend = 0.05). Despite a small number of cases, risk of columnar cell lesions also suggested an inverse association with strenuous activity (RR for 4 or more hours of strenuous activity per week = 0.62; 0.31-1.22 compared to < 1 h per week).

CONCLUSIONS

This study suggests that exercise may be inversely associated with the risk of developing proliferative benign breast disease, one of the earliest steps in the development of breast cancer.

Plasma 25-hydroxyvitamin D and risk of breast cancer in the Nurses' Health Study II

Introduction

Experimental evidence indicates vitamin D may play an important role in breast cancer etiology but epidemiologic evidence to date is inconsistent. Vitamin D comes from dietary intake and sun exposure and plasma levels of 25-hydroxyvitamin D (25(OH)D) are considered the best measure of vitamin D status.

Methods

We conducted a prospective nested case-control study within the Nurses' Health Study II (NHSII). Plasma samples collected in 1996 to 1999 were assayed for 25(OH)D in 613 cases, diagnosed after blood collection and before 1 June 2007, and in 1,218 matched controls. Multivariate relative risks (RR) and 95% confidence intervals (CI) were calculated by conditional logistic regression, adjusting for several breast cancer risk factors.

Results

No significant association was observed between plasma 25(OH)D levels and breast cancer risk (top vs. bottom quartile multivariate RR = 1.20, 95% CI (0.88 to 1.63), P-value, test for trend = 0.32). Results were similar when season-specific quartile cut points were used. Results did not change when restricted to women who were premenopausal at blood collection or premenopausal at diagnosis. Results were similar between estrogen receptor (ER)+/progesterone receptor (PR)+ and ER-/PR- tumors (P-value, test for heterogeneity = 0.51). The association did not vary by age at blood collection or season of blood collection, but did vary when stratified by body mass index (P-value, test for heterogeneity = 0.01).

Conclusions

Circulating 25(OH)D levels were not significantly associated with breast cancer risk in this predominantly premenopausal population.

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.

Recommendations for a lifestyle which could prevent breast cancer and its relapse: physical activity and dietetic aspects

External factors such as eating habits and physical activity have an important impact on breast cancer risk. This paper reviews the literature on the relationship between breast cancer and lifestyle. It aims to produce recommendations regarding physical activity and dietary intake for clinical practice. Although strong clinical evidence of the impact of lifestyle modifications is still lacking, practising healthy eating should be encouraged for the prevention of cancer, its occurrence or relapse. Physical activity is recommended to avoid excessive weight gain. For example, the beneficial effects on the risk of breast cancer could be achieved by walking half an hour per day. Three to five hours per week of moderate physical exercise therefore should be recommended for optimising the reduction of the risk of cancer. For most women, moderate to intense activity, such as heavy housework, brisk walking, or dancing, could provide an effective level of activity to keep reduce the risk of breast cancer.

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.

Benign breast disease

Benign breast diseases are among the most common diagnoses that the busy obstetrician-gynecologist will see in practice. Moreover, breast cancer will undoubtedly be diagnosed numerous times in an obstetrician-gynecologist's career. An ability to accurately and promptly diagnose both benign and malignant breast diseases is within the purview of the generalist obstetrician-gynecologist. A thorough understanding of benign breast diseases, including appropriate diagnostic techniques, is vitally important in well-women care. In addition, a working knowledge of breast cancer risk factors with the ability to identify women at high risk and either refer or initiate risk reduction methods is equally important. This review outlines common benign breast diseases stratified by future risk of breast cancer and discusses appropriate management after diagnosis.

Epidemiology of breast cancer in young women

Breast cancer is mainly a postmenopausal disease, but in younger women breast tumors often exhibit more aggressive features and worse prognosis. Furthermore, high-risk and low-risk tumors present different age distributions suggesting that breast cancer comprises a mixture of two different disease processes. In agreement with this hypothesis, breast cancer presents different epidemiologic traits in pre- and postmenopausal women. Regarding racial distribution, incidence is higher in black women at younger ages in US, while the reverse is true among women older than 50 years. Genetic predisposition is a stronger risk factor in young women. On the contrary, nulliparity and obesity decrease the risk of early-onset breast cancers while are associated with higher incidence in older women. Epidemiologic data related with the hormonal exposure in utero suggest that the effect is stronger in early breast cancers. In most developed countries, breast cancer has shown an upward trend until recent years in postmenopausal women, while incidence rates in younger women have been stable. However, Spain is an exception to this rule: Spanish women younger than 45 years of age have registered a steady increase of breast cancer that may be related with the remarkable lifestyle changes experienced by women born in the second half of the twentieth century.

Systematic Development of the YouRAction program, a computer-tailored physical activity promotion intervention for Dutch adolescents, targeting personal motivations and environmental opportunities

BACKGROUND

Increasing physical activity (PA) among adolescents is an important health promotion goal. PA has numerous positive health effects, but the majority of Dutch adolescents do not meet PA requirements. The present paper describes the systematic development of a theory-based computer-tailored intervention, YouRAction, which targets individual and environmental factors determining PA among adolescents.

DESIGN

The intervention development was guided by the Intervention Mapping protocol, in order to define clear program objectives, theoretical methods and practical strategies, ensure systematic program planning and pilot-testing, and anticipate on implementation and evaluation. Two versions of YouRAction were developed: one that targets individual determinants and an extended version that also provides feedback on opportunities to be active in the neighbourhood. Key determinants that were targeted included: knowledge and awareness, attitudes, self-efficacy and subjective norms. The extended version also addressed perceived availability of neighbourhood PA facilities. Both versions aimed to increase levels of moderate-to-vigorous PA among adolescents. The intervention structure was based on self-regulation theory, comprising of five steps in the process of successful goal pursuit. Monitoring of PA behaviour and behavioural and normative feedback were used to increase awareness of PA behaviour; motivation was enhanced by targeting self-efficacy and attitudes, by means of various interactive strategies, such as web movies; the perceived environment was targeted by visualizing opportunities to be active in an interactive geographical map of the home environment; in the goal setting phase, the adolescents were guided in setting a goal and developing an action plan to achieve this goal; in the phase of active goal pursuit adolescents try to achieve their goal and in the evaluation phase the achievements are evaluated. Based on the results of the evaluation adolescents could revise their goal or choose another behaviour to focus on. The intervention is delivered in a classroom setting in three lessons. YouRAction will be evaluated in a cluster-randomized trial, with classes as unit of randomization. Evaluation will focus on PA outcomes, cognitive mediators/moderators and process measures.

DISCUSSION

The planned development of YouRAction resulted in two computer-tailored interventions aimed at the promotion of PA in a Dutch secondary school setting.

TRIAL REGISTRATION

NTR1923.

Prevention of breast cancer (part I): epidemiology, risk factors, and risk assessment tools

Advances in breast cancer research have led to declining death rates from this disease because of early detection through mammographic screening and improved therapy for breast cancer. The concept that breast cancer, in some cases, can be prevented has been explored over the last three decades. This article, part I of a two-part series, will focus on the epidemiology, the risk factors associated with breast cancer, and the available risk assessment tools, which can help define who should be considered for risk reduction strategies. Part II will focus on discussing risk reduction strategies.

Time course of risk factors in cancer etiology and progression

Patients with cancer increasingly ask what they can do to change their lifestyles and improve outcomes. Risk factors for onset of cancer may differ substantially from those that modify survival with implications for counseling. This review focuses on recent data derived from population-based studies of causes of cancer and of patients with cancer to contrast risk factors for etiology with those that impact survival. For different cancer sites, the level of information to inform the timing of lifestyle exposures and risk of disease onset or progression after diagnosis is often limited. For breast cancer, timing of some exposures, such as radiation, is particularly important. For other exposures, such as physical activity, higher levels may prevent onset and also improve survival. For colon cancer, study of precursor polyps has provided additional insight to timing. Extensive data indicate that physical activity reduces risk of colon cancer, and more limited data suggest that exposure after diagnosis improves survival. Dietary factors including folate and calcium may also reduce risk of onset. More limited data on prostate cancer point to obesity increasing risk of aggressive or advanced disease. Timing of change in lifestyle for change in risk of onset and for survival is important but understudied among patients with cancer. Counseling patients with cancer to increase physical activity and avoid weight gain may improve outcomes. Advice to family members on lifestyle may become increasingly important for breast and other cancers where family history is a strong risk factor.

Intensity and timing in life of recreational physical activity in relation to breast cancer risk among pre- and postmenopausal women

Regular recreational physical activity has been found to be associated with a decrease in breast cancer risk in women in the majority of epidemiologic studies, but research findings are inconsistent regarding the intensity of activity and timing in life. To address these issues the relations of moderate and vigorous intensity recreational physical activity during ages 14-20, 21-34, 35-50, and over age 50 years to pre- and postmenopausal breast cancer risk were examined. A case-control study of 858 women, with histological confirmation of invasive breast cancer, and 1085 controls, free of any cancer diagnosis, all subjects aged 28-79 years was conducted in the Region of Western Pomerania (Poland). Physical activity was assessed using a self-administered questionnaire with questions on type of activity, duration, frequency, and intensity for each type of activity. Odds ratios (OR) and 95% confidence intervals (CI) of breast cancer associated with physical activity were calculated using unconditional logistic regression. Vigorous physical activity at ages 14-20 and 21-34 years lowered breast cancer risk by at least 35% in premenopausal women and by at least 51% in postmenopausal women for the highest versus lowest quartiles of the activity. The risk was also reduced in postmenopausal women who reported on average more than 1.74 hours per week of vigorous intensity recreational activity in ages >50 years (OR = 0.58; 95%CI = 0.27-0.97; P for trend = 0.013). For moderate activity the relationships remained statistically significant only in postmenopausal women active during ages 14- 20 years. The results indicate also a plausible risk reduction among premeno-pausal women. These results support the hypothesis that recrea-tional activity, particularly done early in life, is associated with a decrease in the invasive breast cancer risk in postmenopausal women. Among premenopausal women, only vigorous forms of activity may significantly decrease the risk. Key pointsRecreational physical activity of vigorous intensity during ages 14-20 and 21-34 years protect against breast cancer regardless of menopausal status.Vigorous recreational physical activity at ages >50 years was also associated with reduced postmeno-pausal breast cancer risk.The risk reduction was also observed among post-menopausal women engaged in recreational physical activity of moderate intensity at ages 14-20 years.