A pan-Canadian prospective study of young women with breast cancer: the rationale and protocol design for the RUBY study

Introduction

The understanding of the biology and epidemiology of, and the optimal therapeutic strategies for, breast cancer (bca) in younger women is limited. We present the rationale, design, and initial recruitment of Reducing the Burden of Breast Cancer in Young Women (ruby), a unique national prospective cohort study designed to examine the diagnosis, treatment, quality of life, and outcomes from the time of diagnosis for young women with bca.

Methods

Over a 4-year period at 33 sites across Canada, the ruby study will use a local and virtual recruitment model to enrol 1200 women with bca who are 40 years of age or younger at the time of diagnosis, before initiation of any treatment. At a minimum, comprehensive patient, tumour, and treatment data will be collected to evaluate recurrence and survival. Patients may opt to complete patient-reported questionnaires, to provide blood and tumour samples, and to be contacted for future research, forming the core dataset from which 4 subprojects evaluating genetics, lifestyle factors, fertility, and local management or delivery of care will be performed.

Summary

The ruby study will be the most comprehensive repository of data, biospecimens, and patient-reported outcomes ever collected with respect to young women with bca from the time of diagnosis, enabling research unique to that population now and into the future. This research model could be used for other oncology settings in Canada.

Role of exercise training in polycystic ovary syndrome: a systematic review and meta-analysis

Preliminary evidence suggests exercise in polycystic ovary syndrome (PCOS) may improve reproductive and cardiometabolic parameters. Our primary aim was to determine the impact of exercise training on reproductive health in women with PCOS. Our secondary aim was to determine the effect of exercise training on cardiometabolic indices. A systematic review of published literature was conducted using MEDLINE and EMBASE based on a pre-published protocol (PROSPERO CRD42017065324). The search was not limited by year. Randomized controlled trials, non-randomized controlled trials and uncontrolled trials that evaluated an exercise intervention in women with PCOS and reported reproductive outcomes were included. Reproductive outcomes were analysed semi-quantitatively and a meta-analysis was conducted for reported cardiometabolic outcomes. Of 517 screened abstracts, 14 studies involving 617 women with PCOS were included: seven randomized controlled trials, one non-randomized controlled trial and six uncontrolled trials. There were insufficient published data to describe the effect of exercise interventions on ovulation quantitatively, but semi-quantitative analysis suggested that exercise interventions may improve menstrual regularity, pregnancy and ovulation rates. Our meta-analysis found that exercise improved lipid profiles and decreased waist circumference, systolic blood pressure and fasting insulin. The impact of exercise interventions on reproductive function remains unclear. However, our meta-analysis suggests that exercise interventions may improve cardiometabolic profiles in women with PCOS.

Sleep and Cancer Incidence in Alberta's Tomorrow Project Cohort

We aimed to investigate the association between self-reported sleep duration and sleep timing midpoint with all- and site-specific cancer incidence in Alberta's Tomorrow Project (ATP) cohort. Methods: The analysis for sleep duration included 46,300 Albertans aged 35–65 years at baseline from the ATP cohort recruited from 2001–2015. Sleep timing midpoint (wake-time – ½ sleep duration) was assessed in a subset of ATP participants (n = 19,820). Cancer incidence was determined through record linkage with the Alberta Cancer Registry in December 2016. Cox proportional hazard regression models evaluated the effects of sleep duration and sleep timing midpoint categories on all- and site-specific (breast, colorectal, lung, prostate, endometrial and hematologic) cancer incidence. Models were adjusted for age, sex (non sex-specific cancers), highest level of education, total household income, marital status, alcohol intake, smoking status, body mass index, family history of cancer, presence of at least one medical condition/co-morbidity, menopausal status (female cancers only) and sleep duration (sleep timing midpoint analysis only). Results: By 2016, there were 3,034 incident cases of cancer in this cohort. A statistical trend was noted for an increased risk of all cancers in participants reporting > 9 hours of sleep/night compared to 7–9 hours of sleep/night (hazard ratio (HR) = 1.16, 95% confidence interval (CI): 0.98–1.36; P = 0.08). Reporting > 9 hours of sleep/night compared to 7–9 hours of sleep/night was also associated with an increased incidence of endometrial cancer (HR = 2.09, 95% CI: 1.16–3.76; P = 0.01). A later sleep timing midpoint (>4:08 AM) versus an intermediate sleep timing midpoint (3:47 AM–4:08 AM) was associated with an increased risk of all (HR = 1.19, 95% CI: 1.03–1.37; P = 0.02) and breast (HR = 1.64, 95% CI: 1.18–2.26; P = 0.003) cancer incidence. Conclusions: These novel findings provide evidence regarding the important role of sleep in cancer etiology. Interventions that put emphasis on proper sleep hygiene for cancer prevention are needed.

Dose–response effects of aerobic exercise on energy compensation in postmenopausal women: combined results from two randomized controlled trials

Background/objectives:

Despite the clear health benefits of exercise, exercised-induced weight loss is often less than expected. The term ‘exercise energy compensation’ is used to define the amount of weight loss below what is expected for the amount of exercise energy expenditure. We examined the dose–response effects of exercise volume on energy compensation in postmenopausal women.

Participants/methods:

Data from Alberta Physical Activity and Breast Cancer Prevention (ALPHA) and Breast Cancer and Exercise Trial in Alberta (BETA) were combined for the present analysis. The ALPHA and BETA trials were two-centred, two-armed, 12-month randomized controlled trials. The ALPHA trial included 160 participants randomized to 225 min per week of aerobic exercise, and the BETA trial randomized 200 participants to each 150 and 300 min per week of aerobic exercise. All participants were aged 50–74 years, moderately inactive (<90 min per week of exercise), had no previous cancer diagnosis and a body mass index between 22 and 40 kg m⁻². Energy compensation was based on changes in body composition (dual-energy X-ray absorptiometry scan) and estimated exercise energy expenditure from completed exercise volume. Associations between Δenergy intake, ΔVO_2peak and Δphysical activity time with energy compensation were assessed.

Results:

No differences in energy compensation were noted between interventions. However, there were large inter-individual differences in energy compensation between participants; 9.4% experienced body composition changes that were greater than expected based on exercise energy expenditure, 64% experienced some degree of energy compensation and 26.6% experienced weight gain based on exercise energy expenditure. Increases in VO_2peak were associated with reductions in energy compensation (β=−3.44 ml kg⁻¹ min⁻¹, 95% confidence interval for β=−4.71 to −2.17 ml kg⁻¹ min⁻¹; P=0.0001).

Conclusions:

Large inter-individual differences in energy compensation were noted, despite no differences between activity doses. In addition, increases in VO_2peak were associated with lower energy compensation. Future studies are needed to identify behavioral and metabolic factors that may contribute to this large inter-individual variability in energy compensation.

Infertility and incident endometrial cancer risk: a pooled analysis from the epidemiology of endometrial cancer consortium (E2C2)

BACKGROUND

Nulliparity is an endometrial cancer risk factor, but whether or not this association is due to infertility is unclear. Although there are many underlying infertility causes, few studies have assessed risk relations by specific causes.

METHODS

We conducted a pooled analysis of 8153 cases and 11 713 controls from 2 cohort and 12 case-control studies. All studies provided self-reported infertility and its causes, except for one study that relied on data from national registries. Logistic regression was used to estimate adjusted odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

Nulliparous women had an elevated endometrial cancer risk compared with parous women, even after adjusting for infertility (OR=1.76; 95% CI: 1.59-1.94). Women who reported infertility had an increased risk compared with those without infertility concerns, even after adjusting for nulliparity (OR=1.22; 95% CI: 1.13-1.33). Among women who reported infertility, none of the individual infertility causes were substantially related to endometrial cancer.

CONCLUSIONS

Based on mainly self-reported infertility data that used study-specific definitions of infertility, nulliparity and infertility appeared to independently contribute to endometrial cancer risk. Understanding residual endometrial cancer risk related to infertility, its causes and its treatments may benefit from large studies involving detailed data on various infertility parameters.

Physical activity, sex steroid, and growth factor concentrations in pre- and post-menopausal women: a cross-sectional study within the EPIC cohort

PURPOSE

Increased physical activity (PA) is associated with a reduced risk of several cancers. PA may reduce cancer risk by changing endogenous hormones levels, but relatively little research has focused on this topic. The purpose of this study was to elucidate the relation between PA and endogenous hormone concentrations.

METHODS

A cross-sectional analysis of 798 pre- and 1,360 post-menopausal women included as controls in case-control studies on endogenous hormones (steroids, progesterone, sex-hormone-binding globulin (SHBG), and growth factors) levels, and cancer risk nested within European Prospective Investigation into Cancer and Nutrition cohort was performed. Multivariate regression analyses were performed to compare geometric mean levels of hormones and SHBG by categories of PA.

RESULTS

In pre-menopausal women, active women had 19 % significantly lower concentrations of androstenedione, 14 % lower testosterone, and 20 % lower free testosterone than inactive women, while no differences were observed for estrogens, progesterone, SHBG, and growth factors. In post-menopausal women, active women had 18 % significantly lower estradiol and 20 % lower free estradiol concentrations than inactive women, while no differences were observed for the other hormones and SHBG. More vigorous forms of physical activity were associated with higher insulin-like growth factor-I concentrations. Adjustment for body mass index did not alter the associations. Overall, the percentage of variance in hormone concentrations explained by PA levels was <2 %.

CONCLUSIONS

Our results support the hypothesis of an influence, although small in magnitude, of PA on sex hormone levels in blood, independent of body size.

Abstract P4-08-01: Effects of exercise during adjuvant chemotherapy on clinical outcomes in early stage breast cancer

Background: Observational studies suggest that physical activity following a diagnosis of breast cancer may be associated with a lower risk of recurrence and death. Some studies also suggest possible effect modification by disease stage, body mass index, and receptor status. To date, however, there are no randomized trials examining the effects of exercise on disease outcomes in any cancer patient group. Here, we report an exploratory follow-up of disease outcomes from the Supervised Trial of Aerobic versus Resistance Training (START). Patients and Methods: The START Trial was a Canadian multicenter trial that randomized 242 breast cancer patients starting adjuvant chemotherapy to either usual care (n = 82) or supervised aerobic (n = 78) or resistance (n = 82) exercise for the duration of their chemotherapy. The primary efficacy endpoint for this exploratory analysis was disease-free survival (DFS). Secondary endpoints were overall survival (OS), distant disease-free survival (DDFS), and recurrence-free interval (RFI). The two exercise arms were combined for the analysis (n = 160) and selected subgroups were explored. Results: After a median follow-up of 89 months (IQR 81 to 96), there were 25/160 (15.6%) DFS events in the exercise groups and 18/82 (22.0%) in the control group (log-rank p = 0.21). Eight-year DFS was 82.7% for the exercise groups compared with 75.6% for the control group (Hazard ratio [HR] = 0.68, 95% CI = 0.37-1.24). There were 13/160 (8.1%) deaths in the exercise groups and 11/82 (13.4%) in the control group (log-rank p = 0.21). Eight-year OS was 91.2% in the exercise groups compared with 82.7% in the control group (HR = 0.60, 95% CI = 0.27 to 1.33. There were 20/160 (12.5%) DDFS events in the exercise groups and 16/82 (19.5%) in the control group (log-rank p = 0.15). Eight-year DDFS was 86.7% in the exercise groups compared with 78.3% in the control group (HR = 0.62, 95% CI = 0.32 to 1.19). Finally, there were 20/160 (12.5%) RFI events in the exercise groups and 17/82 (20.7%) in the control group (Gray's p = 0.095). Eight-year cumulative incidence of RFI was 12.6% in the exercise groups compared with 21.6% in the control group (HR = 0.58, 95% CI = 0.30 to 1.11). Subgroup analyses for DFS and RFI suggested stronger effects for women who were overweight/obese, had stage II/III cancer, receptor positive tumors, HER2 positive tumors, received taxane-based chemotherapies, and received at least 85% of their intended chemotherapy dose-intensity. The most notable subgroup effect was for patients who received optimal chemotherapy dosing with a borderline significant effect for DFS (HR = 0.50, 95% CI = 0.25 to 1.01) and a significant effect for RFI (HR = 0.38, 95% CI = 0.18 to 0.81). Conclusions: In this exploratory follow-up of the START Trial, there was a suggestion that exercise during adjuvant chemotherapy may improve several efficacy endpoints although none achieved statistical significance. Nevertheless, the magnitude of the effects appear to be meaningful with absolute 8-year survival differences between 7% and 9% and relative rate reductions between 30% and 40%. The START Trial provides the first randomized data to suggest that adding exercise to standard chemotherapy for breast cancer may improve outcomes. A definitive phase III trial is warranted.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-08-01.

The etiology of uterine sarcomas: a pooled analysis of the epidemiology of endometrial cancer consortium

BACKGROUND

Uterine sarcomas are characterised by early age at diagnosis, poor prognosis, and higher incidence among Black compared with White women, but their aetiology is poorly understood. Therefore, we performed a pooled analysis of data collected in the Epidemiology of Endometrial Cancer Consortium. We also examined risk factor associations for malignant mixed mullerian tumours (MMMTs) and endometrioid endometrial carcinomas (EECs) for comparison purposes.

METHODS

We pooled data on 229 uterine sarcomas, 244 MMMTs, 7623 EEC cases, and 28,829 controls. Odds ratios (ORs) and 95% confidence intervals (CIs) for risk factors associated with uterine sarcoma, MMMT, and EEC were estimated with polytomous logistic regression. We also examined associations between epidemiological factors and histological subtypes of uterine sarcoma.

RESULTS

Significant risk factors for uterine sarcoma included obesity (body mass index (BMI)≥30 vs BMI<25 kg m(-2) (OR: 1.73, 95% CI: 1.22-2.46), P-trend=0.008) and history of diabetes (OR: 2.33, 95% CI: 1.41-3.83). Older age at menarche was inversely associated with uterine sarcoma risk (≥15 years vs <11 years (OR: 0.70, 95% CI: 0.34-1.44), P-trend: 0.04). BMI was significantly, but less strongly related to uterine sarcomas compared with EECs (OR: 3.03, 95% CI: 2.82-3.26) or MMMTs (OR: 2.25, 95% CI: 1.60-3.15, P-heterogeneity=0.01).

CONCLUSION

In the largest aetiological study of uterine sarcomas, associations between menstrual, hormonal, and anthropometric risk factors and uterine sarcoma were similar to those identified for EEC. Further exploration of factors that might explain patterns of age- and race-specific incidence rates for uterine sarcoma are needed.

Prevalence of meeting physical activity guidelines for cancer prevention in Alberta

INTRODUCTION

Guidelines for recommended physical activity (PA) levels have been developed by the Canadian Society for Exercise Physiology (CSEP) and the U.S. Department of Health and Human Services (USDHHS) for health benefits and by the American Cancer Society (ACS) and the World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) for cancer prevention benefits.

METHODS

We examined if these guidelines were met using a sample of 14 294 Albertan participants of the Tomorrow Project, aged 35 to 64 years, enrolled from 2001 to 2005. We used logistic regression to examine correlates of leisure PA behaviour.

RESULTS

An estimated 55%, 42%, 26% and 23% of participants met CSEP, ACS, USDHHS, and WCRF/AICR guidelines, respectively. Women were less likely than men to meet ACS (Odds Ratio [OR] = 0.72, 95% confidence interval [CI]: 0.55-0.93), USDHHS (OR = 0.67, 95% CI: 0.50-0.89) and WCRF/AICR (OR = 0.63, 95% CI: 0.47-0.85) guidelines, and being obese was correlated with not meeting USDHHS (OR = 0.45, 95% CI: 0.32-0.65) and WCRF/AICR guidelines (OR = 0.79, 95% CI: 0.63-0.98).

CONCLUSION

Albertans, particularly women and obese individuals, are not sufficiently active for cancer prevention benefits.

Medical, demographic and social cognitive correlates of physical activity in a population-based sample of colorectal cancer survivors

Physical activity (PA) improves quality of life in colorectal cancer survivors (CRC) and may reduce the risk of disease recurrence and early death. Few studies, however, have examined the correlates of PA in CRC survivors. Using the Alberta Cancer Registry, 2000 randomly selected CRC survivors were mailed a self-reported questionnaire assessing medical, demographic, behavioural and social cognitive variables from the theory of planned behaviour (TPB). Of the 600 survivors who responded, 33% were meeting public health PA guidelines and almost half were completely sedentary. Higher PA was reported by survivors who were younger, unmarried, better educated, wealthier, employed, non-smokers, social drinkers, not treated with radiation therapy, disease-free, in better health and less comorbidity. In multivariate path analysis, these variables were not directly associated with PA after controlling for the TPB variables. The TPB explained 34% (P < 0.001) of the variance in PA behaviour with direct associations for intention (β= 0.22; P= 0.015) and planning (β= 0.18; P= 0.001). Intention, in turn, had 62% (P < 0.001) of its variance explained by perceived behavioural control (β= 0.43; P < 0.001), affective attitude (β= 0.25; P < 0.001) and instrumental attitude (β= 0.15; P < 0.001). The TPB may be a useful framework for developing population-based interventions to increase PA in CRC survivors.

Adiposity changes after a 1-year aerobic exercise intervention among postmenopausal women: a randomized controlled trial

Objective:

We examined the effects of an aerobic exercise intervention on adiposity outcomes that may be involved in the association between physical activity and breast cancer risk.

Design:

This study was a two-centre, two-armed, randomized controlled trial. The 1-year-long exercise intervention included 45 min of moderate-to-vigorous aerobic exercise five times per week, with at least three of the sessions being facility based. The control group was asked not to change their activity and both groups were asked not to change their diet.

Subjects:

A total of 320 postmenopausal, sedentary, normal weight-to-obese women aged 50–74 years who were cancer-free, nondiabetic and nonhormone replacement therapy users were included in this study.

Measurements:

Anthropometric measurements of height, weight and waist and hip circumferences; dual energy X-ray absorptiometry measurements of total body fat; and computerized tomography measurements of abdominal adiposity were carried out.

Results:

Women in the exercise group exercised a mean of 3.6 days (s.d.=1.3) per week and 178.5 min (s.d.=76.1) per week. Changes in all measures of adiposity favored exercisers relative to controls (P<0.001). The mean difference between groups was: −1.8 kg for body weight; −2.0 kg for total body fat; −14.9 cm² for intra-abdominal fat area; and −24.1 cm² for subcutaneous abdominal fat area. A linear trend of greater body fat loss with increasing volume of exercise was also observed.

Conclusion:

A 1-year aerobic exercise program consistent with current public health guidelines resulted in reduced adiposity levels in previously sedentary postmenopausal women at higher risk of breast cancer.

The Colon Health and Life-Long Exercise Change trial: a randomized trial of the National Cancer Institute of Canada Clinical Trials Group

Background

Observational studies indicate that physical activity (pa) is strongly associated with improved disease outcomes in colon cancer survivors, but a randomized controlled trial is needed to determine whether the association is causal and whether new policies to promote exercise are justified.

Purpose

The co.21 Colon Health and Life-Long Exercise Change (challenge) trial undertaken by the National Cancer Institute of Canada Clinical Trials Group (ncic ctg) is designed to determine the effects of a structured pa intervention on outcomes for survivors of high-risk stage ii or iii colon cancer who have completed adjuvant therapy within the previous 2–6 months.

Methods

Trial participants (n = 962) will be stratified by centre, disease stage, body mass index, and performance status, and will be randomly assigned to a structured pa intervention or to general health education materials. The pa intervention will consist of a behavioural support program and supervised pa sessions delivered over a 3-year period, beginning with regular face-to-face sessions and tapering to less frequent face-to-face or telephone sessions. The primary endpoint is disease-free survival. Important secondary endpoints include multiple patient-reported outcomes, objective physical functioning, biologic correlative markers, and an economic analysis.

Summary

Cancer survivors and cancer care professionals are interested in the potential role of PA to improve multiple disease-related outcomes, but a randomized controlled trial is needed to provide compelling evidence to justify changes in health care policies and practice.

Physical activity and breast cancer risk: impact of timing, type and dose of activity and population subgroup effects

OBJECTIVE

To review (1) the epidemiological literature on physical activity and the risk of breast cancer, examining the effect of the different parameters of activity and effect modification within different population subgroups; and (2) the biological mechanisms whereby physical activity may influence the risk of breast cancer.

METHODS

A review of all published literature to September 2007 was conducted using online databases; 34 case-control and 28 cohort studies were included. The impact of the different parameters of physical activity on the association between activity and the risk of breast cancer was examined by considering the type of activity performed, the timing of activity over the life course and the intensity of activity. Effect modification of this association by menopausal status, body mass index (BMI), racial group, family history of breast cancer, hormone receptor status, energy intake and parity were also considered.

RESULTS

Evidence for a risk reduction associated with increased physical activity was found in 47 (76%) of 62 studies included in this review with an average risk decrease of 25-30%. A dose-response effect existed in 28 of 33 studies. Stronger decreases in risk were observed for recreational activity, lifetime or later life activity, vigorous activity, among postmenopausal women, women with normal BMI, non-white racial groups, those with hormone receptor negative tumours, women without a family history of breast cancer and parous women.

CONCLUSIONS

The effect of physical activity on the risk of breast cancer is stronger in specific population subgroups and for certain parameters of activity that need to be further explored in future intervention trials.

Case-control study of lifetime total physical activity and prostate cancer risk

A population-based case-control study of physical activity and prostate cancer risk was conducted in Alberta, Canada, between 1997 and 2000. A total of 988 incident, histologically confirmed cases of stage T2 or greater prostate cancer were frequency matched to 1,063 population controls. The Lifetime Total Physical Activity Questionnaire was used to measure occupational, household, and recreational activity levels from childhood until diagnosis. Multivariable logistic regression analyses were conducted. No association for total lifetime physical activity and prostate cancer risk was found (odds ratio (OR) for > or =203 vs. <115 metabolic equivalent-hours/week/year=0.87, 95% confidence interval (CI): 0.65, 1.17). By type of activity, the risks were decreased for occupational (OR=0.90, 95% CI: 0.66, 1.22) and recreational (OR=0.80, 95% CI: 0.61, 1.05) activity but were increased for household (OR=1.36, 95% CI: 1.05, 1.76) activity when comparing the highest and lowest quartiles. For activity performed at different age periods throughout life, activity done during the first 18 years of life (OR=0.78, 95% CI: 0.59, 1.04) decreased risk. When activity was examined by intensity of activity (i.e., low, <3; moderate, 3-6; and vigorous, >6 metabolic equivalents), vigorous activity decreased prostate cancer risk (OR=0.70, 95% CI: 0.54, 0.92). This study provides inconsistent evidence for the association between physical activity and prostate cancer risk.

A randomized trial of exercise and quality of life in colorectal cancer survivors

We conducted a randomized controlled trial to determine the effects of a home-based exercise intervention on change in quality of life (QOL) in recently resected colorectal cancer survivors, most of whom were receiving adjuvant therapy. Participants were randomly assigned in a 2:1 ratio to either an exercise (n = 69) or control (n = 33) group. The exercise group was asked to perform moderate intensity exercise 3-5 times per week for 20-30 min each time. The primary outcome was change in QOL as measured by the Functional Assessment of Cancer Therapy-Colorectal (FACT-C) scale. Adherence in the exercise group was good (75.8%) but contamination in the control group was problematic (51.6%). Intention-to-treat analysis revealed no significant differences between groups for change in the FACT-C (mean difference, -1.3; 95% CI, -7.8 to 5.1; P = 0.679). In an 'on-treatment' ancillary analysis, we compared participants who decreased versus increased their cardiovascular fitness over the course of the intervention. This analysis revealed significant differences in favour of the increased fitness group for the FACT-C (mean difference, 6.5; 95% CI, 0.4-12.6; P = 0.038). These data suggest that increased cardiovascular fitness is associated with improvements in QOL in colorectal cancer survivors but better controlled trials are needed.

Framework PEACE: an organizational model for examining physical exercise across the cancer experience

The primary purpose of this article is to provide a framework for organizing research on physical exercise and cancer control. A secondary purpose is to use this framework to provide an overview of the extant literature and to offer directions forr future research. The proposed framework, entitled Physical Exercise Across the Cancer Experience (PEACE), divides the cancer experience into 6 time periods: 2 prediagnosis (i.e., prescreening and screening/diagnosis) and 4 postdiagnosis (i.e., pretreatment, treatment, posttreatment, and resumption). Based on these time periods, 8 general cancer control outcomes are highlighted. Two cancer control outcomes occur prediagnosis (i.e., prevention and detection), and 6 occur postdiagnosis (i.e., buffering, coping, rehabilitation, health promotion, palliation, and survival). An overview of the physical exercise literature indicates that only I time period (i.e., prescreening) and cancer control outcome (i.e., prevention) has received significant research attention. Some time periods (i.e., treatment and resumption) and cancer control outcomes (i.e., coping and health promotion) have received modest research attention, whereas other time periods (i.e., screening/diagnosis, pretreatment, and posttreatment) and cancer control outcomes (i.e., detection, buffering, rehabilitation, palliation, and survival) have received only minimal attention. It is hoped that Framework PEACE will stimulate a more comprehensive and in-depth inquiry into the role of physical exercise in cancer control.

Risk factors for benign breast biopsies: a nested case-control study in the Alberta breast screening program

A nested case-control study was conducted to identify risk factors for benign breast biopsies in 382 cases (women with a benign biopsy result) and 399 controls (women who had not undergone a biopsy) who were sampled from the Alberta breast cancer screening program. The breast biopsy specimens of the cases were reviewed by a panel of pathologists, and percent fibroglandular tissue density was assessed. The multivariable odds ratios for the risk of open benign breast biopsy associated with current cigarette smoking was 2.04 (95% CI 1.32-3.13), for ever regular smoking was 1.61 (1.20-2.16), and for passive smoking was 1.41 (0.99-2.02). A risk reduction was found for ever alcohol consumption (0.61 [0.44-0.85]). Some risk reductions were found when the highest and the lowest quintiles of total aerobic recreational activity were compared (0.71 [0.42-1.20]), stair climbing (0.61 [0.37-1.01]) and walking pace (0.13 [0.02-0.741). Lifestyle risk factors may be implicated in the continuum between detection of an abnormality on a screening mammogram and a breast biopsy specimen. By considering these risk factors, breast screening programs may be better able to identify those women who require a breast biopsy and reduce the number of benign breast biopsies.

Influence of physical activity in different age and life periods on the risk of breast cancer

We conducted a population-based case-control study of 1,237 incident breast cancer cases and 1,241 controls in Alberta between 1995 and 1997 to examine the effect of physical activity performed at different ages and life periods on breast cancer risk. In this study, we measured all types of physical activity done throughout life with a questionnaire developed and tested specifically for this study. We found that breast cancer risk was most associated with a risk reduction for activity done later in life, particularly between menopause and the reference year, for which we observed an odds ratio of 0.70 (95% confidence interval = 0.52-0.95). We also stratified the study participants into four categories according to their patterns of physical activity performed before and after menopause. For the women who sustained physical activity throughout life vs those who were never active, we found an odds ratio of 0.58 (95% confidence interval = 0.41-0.83). This study suggests that sustained activity throughout life and particularly activity done later in life may have the most benefit in reducing breast cancer risk.

Physical activity and cancer: lessons learned from nutritional epidemiology

Convincing epidemiologic evidence currently exists for an association between physical activity and the prevention of colon and breast cancer Physical activity may also reduce the risk of cancer at several other sites. With increasing research on this topic, it is apparent that studies of physical activity and cancer have numerous methodological similarities with studies of nutrition and cancer Lessons learned from nutritional epidemiology that can be applied to studies of physical activity and cancer prevention and recommendations for future research are discussed in this review.

Relation between intensity of physical activity and breast cancer risk reduction

PURPOSE

To examine the influence of frequency, duration, and intensity of physical activity on risk of breast cancer and to compare breast cancer risks associated with self-reported versus assigned intensity levels of activity.

METHODS

A population-based case-control study of 1233 incident breast cancer cases and 1241 controls was conducted in Alberta between 1995 and 1997. The frequency, duration and intensity of occupational, household, and recreational activities were measured throughout lifetime using the Lifetime Total Physical Activity Questionnaire and cognitive interviewing methods. Unconditional logistic regression analyses were used to estimate odds ratios and a full assessment of confounding and effect modification was undertaken. Odds ratios for self-reported and compendium-based assigned levels of activity were compared for lifetime total activity and by type of activity.

RESULTS

Breast cancer risk reductions were comparable when self-reported and assigned intensity values were used, although the results and trends were more evident with the assigned intensity data. Moderate-intensity occupational and household activities decreased breast cancer risk, whereas recreational activity, at any intensity level, did not contribute to a breast cancer risk reduction.

CONCLUSION

This study found that moderate-intensity activities were the major contributors to the decrease in breast cancer risk found in this study and that risk reductions were more evident when the frequency and duration of activity alone were modeled. Of the three types of activity considered, the greatest risk reductions observed were for occupational and household activities.

Case-control study of lifetime physical activity and breast cancer risk

A population-based case-control study of 1,233 incident breast cancer cases and 1,237 controls was conducted in Alberta, Canada, in 1995-1997 to examine the effect of lifetime physical activity patterns on breast cancer risk. No associations between physical activity and breast cancer were found for premenopausal women. For postmenopausal women in the highest quartile (> or =161 metabolic equivalent (MET)-hours/week per year) versus the lowest quartile (<104.8 MET-hours/week per year) of lifetime total physical activity, the adjusted odds ratio was 0.70 (95% confidence interval (CI): 0.52, 0.94). When the risks associated with each type of activity were examined for postmenopausal women, household and occupational activity conferred the largest risk reductions (odds ratio (OR) = 0.57, 95% CI: 0.41, 0.79 and OR = 0.59, 95% CI: 0.44, 0.81, respectively, for highest vs. lowest quartiles of activity), while recreational activity was not associated with any risk reductions. For postmenopausal women, the authors found stronger risk reductions for those who were also nonsmokers (OR = 0.64, 95% CI: 0.46, 0.88), non-alcohol-drinkers (OR = 0.39, 95% CI: 0.11, 0.77), or nulliparous (OR = 0.22, 95% CI: 0.07, 0.70) when they compared the highest with the lowest quartile of lifetime total physical activity. This study provides evidence that lifetime total activity reduces risk of postmenopausal breast cancer.

A review of physical activity and prostate cancer risk

OBJECTIVES

The purpose was to review the etiologic role and the possible biologic mechanisms for physical activity in the primary prevention of prostate cancer and to identify future research priorities.

METHODS

We conducted literature searches and systematically reviewed all the epidemiologic studies of physical activity and prostate cancer and the literature on the underlying biologic mechanisms.

RESULTS

Among 24 previously conducted studies, 14 studies suggested an inverse association of physical activity on prostate cancer; however, no overall association was found in six studies and an increased risk of prostate cancer was observed amongst the most physically active men in four other studies. The methodologic limitations in these studies include variations in detection of latent disease and possible outcome misclassification, crude assessments of physical activity, inadequate control for confounding, and incomplete examination of effect modification.

CONCLUSIONS

Physical activity may have an inverse association with prostate cancer risk; however, the epidemiologic evidence is currently inconsistent and the magnitude of the risk reduction observed is small. These inconsistent results could be attributable, in part, to methodologic limitations of previous studies. Hence, further investigation of the etiologic role of physical activity is needed before more definitive conclusions can be made. Specifically, research studies should be designed to measure all types and parameters of physical activity throughout lifetimes. Furthermore, a better understanding of the biologic mechanisms and etiologically relevant time periods in prostate carcinogenesis when physical activity may be operative is needed, so that these studies can be properly designed.

Physical activity and cancer prevention: from observational to intervention research

The purpose of this review is to articulate how progress in epidemiological research on physical activity and cancer prevention can be made. This report briefly reviews the accumulated evidence for an etiological role of physical activity in the prevention of cancer of the colon, breast, prostate, testes, lung, endometrium, and ovary and summarizes the evidence for a causal association for each of these sites. The evidence for a causal association between physical activity and colon and breast cancers is found to be "convincing," for prostate cancer to be "probable," for lung and endometrial cancers to be "possible," and for testicular and ovarian cancers to be currently "insufficient" to make any definitive conclusions. The emerging literature on physical activity and cancer prevention intervention studies is presented, and an overview of the literature on physical activity intervention is also provided. Given the level of evidence that is currently available for the associations between physical activity and cancer, it is argued that for additional progress to be made in this field, there need to be intervention studies on physical activity and cancers of the colon and breast. For the remaining cancer sites, better designed observational epidemiological studies are needed that address the identified methodological limitations found in previous studies. These limitations include crude and incomplete physical activity assessment, lack of adequate control for confounding and effect modification, as well as a lack of consideration of the underlying biological mechanisms that are operative. This review concludes with detailed recommendations for future research in this field.

Review of anthropometric factors and breast cancer risk

Epidemiological evidence implicating anthropometric risk factors in breast cancer aetiology is accumulating. For premenopausal women, breast cancer risk increases with increasing height, but decreases with higher weight or body mass index, and no association with increased central adiposity exists. For postmenopausal women, an increased risk of breast cancer is found with increasing levels of all the anthropometric variables including height, weight, body mass index, waist-hip ratio, waist circumference and weight gain. Weight loss appears to decrease risk, particularly if it occurs later in life. Breast size may be a risk factor for breast cancer, however, the current evidence is inconclusive. Several hypothesized biologic mechanisms exist to explain how anthropometric factors influence breast cancer risk. Obesity may increase levels of circulating endogenous sex hormones, insulin and insulin-like growth factors that all, in turn, increase breast cancer risk. Genetic predisposition to obesity and to specific body fat distributions are also implicated. With obesity, there are increased levels of fat tissue that can store toxins and can serve as a continuous source of carcinogens. Recommendations for future research on anthropometric factors and breast cancer are provided. Sufficient evidence exists to support strategies to avoid weight gain throughout life as a means of reducing postmenopausal breast cancer risk.

Physical exercise and quality of life following cancer diagnosis: a literature review

With almost 8 million Americans alive today who have been through the cancer experience, it is important to develop interventions to maintain quality of life (QOL) following cancer diagnosis. Physical exercise is an intervention that may address the broad range of QOL issues following cancer diagnosis including physical, functional, psychological, emotional, and social well-being. The purpose of the present article was to provide a comprehensive and critical review of the topic and to offer suggestions for future research. The review located 24 empirical studies published between 1980 and 1997. Eighteen of the studies were interventions (i.e. quasi-experimental or experimental) but most of these were preliminary efficacy studies that suffered from the common limitations of such designs. Overall, however, the studies have consistently demonstrated that physical exercise has a positive effect on QOL following cancer diagnosis, including physical and functional well-being (e.g. functional capacity, muscular strength, body composition, nausea, fatigue) and psychological and emotional well-being (e.g. personality functioning, mood states, self-esteem, and QOL). Besides overcoming the limitations of past research, recommendations for future research included: (a) extending the research beyond breast and early-stage cancers; (b) comparing and integrating physical exercise with other QOL interventions; (c) examining resistance exercises, the timing of the intervention, and contextual factors; (d) expanding the breadth of the QOL indicators examined; and (e) investigating the rates and determinants of recruitment and adherence to an exercise program following cancer diagnosis.

Utility of the theory of planned behavior for understanding exercise during breast cancer treatment

Preliminary evidence indicates that physical exercise may be an effective strategy for helping cancer patients cope with the negative side-effects of their treatment. The purpose of the present study was to examine the utility of the theory of planned behavior in understanding cancer patients' motivation to exercise during treatment. A total of 164 women who had been diagnosed with breast cancer within the previous 2 years participated in the study. A retrospective design was used wherein these women were asked to recall their beliefs and exercise behavior during cancer treatment using a self-administered, mailed questionnaire. Results showed that: (1) the salient beliefs of breast cancer patients concerning exercise were different from those of the healthy population; (2) intention and perceived behavioral control were significant determinants of exercise during cancer treatment; and, (3) attitude and subjective norm were significant determinants of intention. It was concluded that the theory of planned behavior may be a viable framework on which to base interventions designed to promote exercise during cancer treatment. The results of this study are preliminary, however, and more sophisticated research designs to examine this question are warranted.

Epidemiologic issues related to the association between physical activity and breast cancer

A workshop on physical activity and breast cancer was held in November 1997 to review previous epidemiologic research on this topic and to identify new areas for research. This article is the first of three summaries of the workshop's activities. The material reviewed included 21 studies that reported a measure of physical activity in relation to breast cancer outcomes and were published by December 1997. They were identified in a computerized literature search and a "by-hand" review of journals. The study designs, populations, data collection methods, and results were examined and the strengths and limitations of the studies identified. The strengths and limitations are discussed herein, as are recommendations for future research. Fifteen of the 21 studies suggested that physical activity reduces the risk of breast cancer, whereas four studies found no association and two studies found an increased risk of breast cancer associated with physical activity. Specific subgroups of the population may experience a greater decrease in breast cancer with increased levels of physical activity. These include women who are lean, parous, and premenopausal. Some examination of confounding and effect modification was undertaken. Hypothesized biologic mechanisms for this putative association include an effect of physical activity on endogenous hormones, energy balance, and the immune system. The overall evidence supports a reduction in breast cancer risk with increased physical activity. However, numerous questions remain regarding this putative association. These include the underlying biologic model and the parameters of physical activity that are associated with risk, such as the types of activity (occupational, recreational, and household), the components of activity (frequency, intensity, and duration), the time periods in life that are associated with risk reduction, and the important confounders and effect modifiers of this association. Use of intermediate endpoints for breast cancer may be useful in such investigations.

The lifetime total physical activity questionnaire: development and reliability

OBJECTIVE

To develop and test the intra-rater reliability of an interview-administered questionnaire that assesses lifetime patterns of total physical activity including occupational, household, and exercise/sports activities.

METHODS

The questionnaire was developed and pretested using cognitive interviewing techniques on a sample of women with and without previous breast cancer diagnoses. A pilot study was conducted with 115 women who were interviewed twice, 6 to 8 wk apart by interviewers trained in cognitive interviewing methods. Respondents used recall calendars to record their education, occupations, life events, and physical activity patterns before the interviews. Interviewers helped respondents recall their lifetime exposures, including their occupational, household, and exercise/sports activities, using these calendars and memory-probing strategies. Activity levels were estimated as the average number of hours of activity per week over different time periods. Means and correlation coefficients were estimated and compared for the two time periods.

RESULTS

The questionnaire was found to be highly reliable. The test-retest correlations for hours per week spent in total lifetime physical activity was 0.74, for lifetime occupational activity was 0.87, for household activity was 0.77, and for exercise/sports activities was 0.72.

CONCLUSIONS

This is the first questionnaire to measure lifetime physical activity by collecting data on each type of physical activity separately over lifetime and by measuring frequency, intensity, and duration of each activity. It is also the first physical activity questionnaire to be developed, refined, and administered using cognitive-based methods employed in survey research. Respondents were able to reliably recall their lifetime physical activity patterns. This instrument can be used for any disease outcome for which physical activity may be a risk factor.

Relationship between exercise pattern across the cancer experience and current quality of life in colorectal cancer survivors

The purpose of this study was to identify the main exercise patterns of colorectal cancer survivors across the cancer experience and determine their relationship with current quality of life (QOL). Participants were 130 colorectal cancer survivors who were diagnosed within the previous 4 years and had received adjuvant treatment. Each participant completed a mailed, self-administered questionnaire that assessed exercise behavior at three time points (prediagnosis, active treatment, posttreatment), current QOL (physical, functional, emotional, social), and overall satisfaction with life (SWL). Colorectal cancer survivors exhibited four main exercise patterns across the cancer experience which were labeled maintainers (active at all three time points), temporary relapsers (active prediagnosis, inactive during treatment, active posttreatment), permanent relapsers (active prediagnosis, inactive during treatment, inactive posttreatment), and nonexercisers (inactive at all three time points). Statistical analyses showed that: (a) functional QOL was the least possessed but most important QOL dimension underlying overall SWL, (b) exercise levels decreased from prediagnosis to active treatment and then increased from active treatment to posttreatment but not back to prediagnosis levels, and (c) permanent relapsers reported the lowest QOL of the four main exercise patterns. It was concluded that cancer treatment has a negative impact on exercise levels and that those previously active individuals who fail to reinitiate exercise after cancer treatment experience the lowest QOL 1 to 4 years later. Findings are discussed in reference to previous research along with suggestions for future research, practical implications, and limitations of the study.

Determinants of exercise during colorectal cancer treatment: an application of the theory of planned behavior

PURPOSE/OBJECTIVES

To examine determinants of exercise during colorectal cancer treatment using the theory of planned behavior.

DESIGN

A retrospective survey.

SETTING

Cancer Registry of Alberta, Canada.

SAMPLE

Randomly selected survivors of colorectal cancer (N = 110) diagnosed between 1992 and 1995 who had undergone adjuvant therapy. Participants' ages ranged from 26 to 77 years (mean = 61 years; SD = 11), 63% were male, and 85% were disease stage II or III.

METHODS

Initial open-ended elicitation questionnaire to determine salient beliefs, a mailed main questionnaire, a postcard reminder one week later, and a second questionnaire three weeks later. Exercise was assessed by the Godin Leisure Time Exercise Questionnaire.

MAIN RESEARCH VARIABLES

Exercise during cancer treatment, intention, perceived behavioral control, attitude, subjective norm, and salient beliefs.

FINDINGS

Exercise during cancer treatment was determined by intention and perceived behavioral control. Intention was determined solely by attitude. Salient beliefs about exercise were different for patients with cancer as compared to a healthy population.

CONCLUSIONS

The theory of planned behavior may be a viable framework on which to base interventions to promote exercise in patients with colorectal cancer.

IMPLICATIONS FOR NURSING PRACTICE

Oncology nurses need to have an understanding of motivational factors related to exercise during cancer treatment to be able to assist patients with cancer to initiate and maintain exercise.

A review of physical activity and breast cancer

Breast cancer risk is influenced by endogenous hormones. Physical activity may offer one means for the primary prevention of breast cancer through its influence on ovarian hormones. This influence is manifested by changes in age at menarche and the number and nature of ovulatory menstrual cycles, factors that themselves are related to breast cancer risk. Animal experimental studies show that breast cancer risk is decreased by exercise at the time of tumor initiation but not necessarily by exercise during tumor promotion. Epidemiologic studies indicate, overall, a decreased risk of breast cancer among those women who are more physically active, whereas experimental studies of the effects of exercise in women have shown that exercise can influence characteristics of the menstrual cycle. Nevertheless, the experimental studies in women and epidemiologic studies of physical activity and breast cancer risk have been hampered by a number of methodologic limitations. The major problems in the epidemiologic studies include crude and incomplete measurements of physical activity over a woman's lifetime and inadequate control for potential confounding factors. Experimental studies of the effects of physical activity on menstrual activity in women have not adequately quantified the intensity of activity and the resultant effects on menstrual cycle changes.

Physical activity and risk of breast cancer

The association between recreational physical activity and breast cancer risk was examined in a population-based case-control study in Adelaide, Australia between 1982 and 1984. There were 451 incident, histologically confirmed cases of breast cancer, identified through the South Australian Central Cancer Registry, which were each age-matched to one control selected at random from the electoral register. These women, aged 20-74 years at diagnosis, reported their level of weekly recreational physical activity in a self-administered questionnaire. The questionnaire reports of light, moderate and vigorous physical activity were converted into total kilocalories per week of energy expenditure. A decrease in risk of breast cancer was found with increasing levels of total recreational physical activity (P (trend) = 0.09). The adjusted odds ratio for those women who expended more than 4,000 kcal/week was 0.73 (95% confidence interval (CI) 0.51-1.05) compared with women who undertook no physical activity. The reduction in risk with recreational physical activity was most evident for women who undertook any vigorous activity. These results provide some support for the hypothesis that physical activity may decrease the risk of developing breast cancer.

Recreational physical activity and risk of benign proliferative epithelial disorders of the breast in women

The association between recreational physical activity and the risk of benign proliferative epithelial disorders (BPED) of the breast was examined in a case-control study conducted in Adelaide, Australia, between 1983 and 1985. The study included 383 incident, histologically confirmed cases of BPED identified through the major private pathology laboratory, 383 unbiopsied community controls matched to the cases for age and area of residence, and 192 controls whose biopsies did not show any signs of epithelial proliferation. Subjects reported their level of usual weekly physical activity in a self-administered questionnaire. When cases were compared with community controls, there was some evidence for a negative association between risk of BPED and total recreational physical activity. However, the reverse was observed when the cases were compared with biopsy controls. These patterns were essentially the same when examined by intensity of activity and by menopausal status. Despite the lack of an association between physical activity and risk BPED in this study, further investigation is warranted because of the potential benefits for the primary prevention of breast disease.

Influence of methodologic factors in a pooled analysis of 13 case-control studies of colorectal cancer and dietary fiber

We examined the study design features and data collection methods from 13 case-control studies of colorectal cancer and diet, which had been previously combined and analyzed, to determine whether they influenced the results obtained from a pooled analysis. We assessed the methods used in each study, estimated a quality score, and used random effects models to re-estimate the pooled odds ratio for the association between dietary fiber and colorectal cancer for these data. Key features of the methods used in each study and the quality score were examined in random effects models to determine whether the heterogeneity found between study-specific risk estimates could be explained by these variables. The odds ratio for dietary fiber and colorectal cancer was 0.46 (95% confidence interval = 0.34-0.64) for the 13 case-control studies as estimated with a random effects model. Two factors, whether the diet questionnaire had been validated before use in the case-control study and whether qualitative data on dietary habits and cooking methods had been incorporated into the nutrient estimation, explained some of the heterogeneity found between studies. Risk estimates for dietary fiber and colorectal cancer were closer to the null for the studies that had these two characteristics. Quality score did not explain any between-study heterogeneity. Random effects models, which included fixed effects covariates, explained some between-study heterogeneity in these data and would be useful for future pooled analyses.

Methodologic issues for pooling dietary data

This paper presents the methodologic issues to consider when conducting a pooled analysis of data from nutritional epidemiologic studies. Because a wide variety of dietary assessment methods have been used in nutritional epidemiology, pooled analyses often combine data collected under very different circumstances. Whether these different methods influence the results obtained in a pooled analysis has not yet been examined. One of the main concerns in a pooled analysis is whether the data to be pooled are comparable. Questions to consider regarding data comparability and methods to address these questions in a pooled analysis are discussed.

Recall bias in the association of micronutrient intake and breast cancer

A nested case-control study within the Canadian National Breast Screening Study was conducted to examine whether there was evidence for recall bias in the reporting of past micronutrient intake. Dietary data collected upon enrollment between 1982 and 1985 from 325 breast cancer cases and 628 matched controls were compared with data collected in 1988 after disease diagnosis. The retrospective estimates of mean micronutrient intakes from food sources were found to be very similar to the prospective estimates for cases and controls. Errors of omission and commission for the reporting of previous supplementary vitamin use were identical for both subject groups. The odds ratios estimated for the association of micronutrient intake and breast cancer for the prospective and retrospective data were similar in magnitude and the 95% confidence intervals overlapped considerably. There was no evidence for recall bias in the estimation of past micronutrient intake by breast cancer cases as compared to controls.

Methods for pooled analyses of epidemiologic studies

This paper presents a systematic methodology for the pooling and analysis of previously conducted epidemiologic studies. It discusses the methodologic issues to consider and the procedures to follow when conducting a pooled analysis of individual subject level data. I review random and fixed effects models to estimate pooled risks and the methods to examine whether heterogeneity in study-specific effect estimates exists. Analytic strategies presented here can be used to assess sources of heterogeneity, particularly those originating from different study designs and methods. I describe methods for incorporating a qualitative assessment of the study design and data collection methods into the quantitative estimation of the overall effect. Finally, I make recommendations for future pooled analyses of epidemiologic studies.

A cohort study of alcohol consumption and risk of breast cancer

The association between alcohol consumption and breast cancer risk was examined in 519 newly incident, histologically confirmed cases of breast cancer diagnosed between 1982 and 1987 within a cohort of 56,837 women enrolled in the Canadian National Breast Screening Study. These women had completed a self-administered food frequency questionnaire including alcohol consumption at enrollment into the study prior to their breast cancer diagnosis. For the total cohort, only a weak association between total alcohol consumption and breast cancer risk is observed, the adjusted relative risk for those drinking 30 or more g/day being 1.22 (95% confidence interval (CI) 0.78-1.90) compared with nondrinkers. There is some evidence for a positive association in women who were premenopausal at the time of enrollment for whom there was a monotonic increase in risk with increasing alcohol intake. Compared with nondrinkers, the adjusted relative risk for alcohol consumption of between 0 and < 10 g of alcohol daily was 1.11 (95% CI 0.71-1.71), between 10 and < 20 g was 1.37 (95% CI 0.79-2.36), between 20 and < 30 g was 1.51 (95% CI 0.80-2.86), and > or = 30 g was 1.86 (95% CI 0.96-3.66; p (trend) = 0.07). These findings contrasted with the results for postmenopausal women where there appeared to be no evidence of any relation. The association in premenopausal women is generally reasonably consistent with that of other studies that have found positive associations with alcohol intake.

Dietary fiber, vitamins A, C, and E, and risk of breast cancer: a cohort study

Risk of breast cancer was examined in relation to intake of dietary fiber and vitamins A, C, and E, and food groups which are sources of these dietary constituents, in a cohort of 56,837 women enrolled in the Canadian National Breast Screening Study. Between 1982 and 1987, 519 incident, histologically confirmed cases of breast cancer were identified among women who previously had completed self-administered dietary questionnaires. Their nutrient and food intake was compared with that of 1,182 women who had not developed breast cancer during the follow-up period. Women at the uppermost quintile level of dietary fiber intake had a 30 percent reduction in risk of breast cancer relative to that for women at the lowest quintile level (adjusted odds ratio = 0.68, 95 percent confidence interval = 0.46-1.00), and the reduction in risk persisted after adjustment (separately) for total vitamin A, beta-carotene, vitamin C, and alpha-tocopherol. Inverse associations of similar magnitude were observed in association with consumption of pasta, cereals (the trend for which was statistically significant), and vegetables rich in vitamins A and C. Smaller, statistically nonsignificant reductions in risk were observed with increasing intake of dietary retinol, beta-carotene, and vitamin C, but the magnitude of these associations was reduced after adjustment for other dietary factors. Vitamin E intake was not associated with altered risk of breast cancer.

The effect of recall bias on the association of calorie-providing nutrients and breast cancer

This nested case-control study conducted within a large dietary cohort study examined whether recall bias could explain the inconsistent results obtained in case-control and cohort studies of the association between dietary fat and breast cancer. Cases were defined as women diagnosed with breast cancer between 1982 and 1987 who had completed a self-administered food frequency questionnaire on enrollment in the cohort study between 1982 and 1985. They were matched to two controls each, and the study subjects were asked in 1988 to complete a second diet questionnaire addressing their diets at the time of enrollment. The mean nutrient intakes for 325 cases who completed the first diet questionnaire six months or more before breast cancer diagnosis and their 628 matched controls were very similar for the prospectively and retrospectively collected diet questionnaires. There was little difference in the magnitude of the odds ratios estimated from the two questionnaires for the association between breast cancer risk and these nutrients. These data do not provide evidence for recall bias in retrospectively collected nutrient data from breast cancer cases compared with their matched controls.

An investigation of recall bias in the reporting of past food intake among breast cancer cases and controls

A nested case-control study was conducted within the Canadian National Breast Screening Study to examine whether there was evidence for biased reporting of past food intake. A total of 325 case patients with breast cancer and 628 matched control subjects completed a self-administered food frequency questionnaire in 1988, recalling their diets originally reported on enrollment into the National Breast Screening Study between 1982 and 1985. Recall of food items was very similar for case patients and control subjects. The magnitude of the odds ratios for the association between these food groups and breast cancer from the prospectively and retrospectively collected data was not systematically different. There was little evidence for recall bias in the reporting of past food intake from these data.

A cohort study of fat intake and risk of breast cancer

Between 1982 and 1987, 519 newly incident, histologically confirmed cases of breast cancer were identified in a cohort of 56,837 women enrolled in the Canadian National Breast Screening Study. These women had completed a dietary questionnaire before the occurrence of their breast cancer, and this has been used to estimate their intake of dietary fat and several other nutrients. There is evidence of a positive association between breast cancer and total fat intake, with a relative risk of 1.35 (95% confidence interval, 1.00-1.82) per 77 g per day, and some evidence of a dose-response relationship (P = .052).