Abstract Introduction and aims To provide a current perspective on nutrition and physical activity influence on breast cancer. Methods and results A comprehensive literature review was conducted and ...selective presentation of findings follows. While some observational studies have associated higher dietary fat intake with higher breast cancer incidence, two full-scale randomized, clinical trials of dietary fat intake reduction programs were negative. However, a lifestyle intervention targeting fat intake reduction in the Women's Intervention Nutrition Study (WINS), resulted in weight loss and also reduced breast cancer recurrences in women with early stage disease. Observational studies evaluating specific nutrient intakes and dietary supplements have provided mixed results. Several observational studies find women with early stage breast cancer with lower 25-hydroxyvitamin D levels at higher recurrence risk, a finding requiring cautious interpretation. The lifestyle factor most strongly and consistently associated with both breast cancer incidence and breast cancer recurrence risk is physical activity. A meta-analyses of observational studies supports the concept that moderate recreational physical activity (about 3–4 h walking per week) may reduce breast cancer incidence and that women with early stage breast cancer who increased or maintain their physical activity may have lower recurrence risk as well. Feasibility of achieving increased physical activity and weight loss in women with early-stage breast cancer has been established. Two full-scale randomized clinical trials are evaluating weight loss/maintenance and increased physical activity in relation to recurrence risk in women with early-stage, resected breast cancer. Discussion/conclusions Dietary intake may influence breast cancer but influence is difficult to separate from influence of body weight. A consistent body of observational study evidence suggests higher physical activity has favorable influence on breast cancer incidence and outcome. While awaiting definitive evidence from ongoing randomized trials, breast cancer patients can reasonably be counseled to avoid weight gain and reduce body weight if overweight or obese and increase or maintain a moderate level of physical activity.
Adherence to oral endocrine therapy in adjuvant breast cancer settings is a substantial clinical problem. To provide current perspective on adherence to oral endocrine therapies, a comprehensive ...literature review was conducted. In adjuvant trials, endocrine therapy adherence is relatively high with greater adherence for aromatase inhibitors compared with tamoxifen. In contrast, adherence to adjuvant therapy in clinical practice is relatively poor, with only about 50% of women successfully completing 5-year therapy. Importantly, good adherence (>80% use) has been associated with lower recurrence risk. Endocrine therapy adherence in primary breast cancer prevention trials parallels that seen in adjuvant trials. Factors associated with nonadherence include low recurrence risk perception, side effects, age extremes, medication cost, suboptimal patient-physician communication, and lack of social support. Few prospective studies have evaluated interventions designed to improve adherence. Interventions currently proposed reflect inferences from clinical trial procedures in which clinical contacts are commonly greater than in usual practice settings. In conclusion, for optimal breast cancer outcome, adherence to endocrine therapy must improve. Although general recommendations likely to improve adherence can be made based on clinical trial results and preliminary prospective trial findings, research specifically targeting this issue is needed to establish effective intervention strategies.
Purpose
Venous thromboembolism (VTE) is the second most common cause of death in hospitalized patients with cancer, and cancer treatments may exacerbate VTE risk. Patients with ...hormone-receptor-positive breast cancer usually receive adjuvant endocrine therapy for 5 years or longer. The aim of this study is to examine VTE risk following long-term use of aromatase inhibitor (AI) compared with tamoxifen use among breast cancer survivors.
Methods
A prospective cohort of 12,904 postmenopausal women who were diagnosed with a first primary hormone-receptor-positive breast cancer and free from previous cardiovascular disease or VTE from 1991 to 2010 were followed through December 2011. Data elements were captured from the comprehensive electronic health records of a large California health plan, Kaiser Permanente. Women who developed deep vein thrombosis (DVT) or pulmonary embolism (PE) were identified as having VTE. We calculated person-year rates of VTE by endocrine therapy groups. Multivariable Cox proportional hazards models were applied to assess the association between time-dependent endocrine therapy and VTE risk.
Results
We identified 623 VTE events during a median follow-up of 5.4 years. The crude rates were 4.6 and 2.8 per 1000 person-years for DVT and PE, respectively. Compared with tamoxifen use, AI use was associated with at least 41% lower VTE risk (adjusted HR 0.59, 95% CI 0.43, 0.81). Greater risk reductions in AI users were seen in women who also underwent adjuvant chemotherapy.
Conclusions
These findings supplement existing evidence to inform treatment decisions that balance cancer control and cardiovascular toxic outcomes.
Rates of obesity have increased significantly over the last three decades in the United States and globally. In addition to contributing to heart disease and diabetes, obesity is a major unrecognized ...risk factor for cancer. Obesity is associated with worsened prognosis after cancer diagnosis and also negatively affects the delivery of systemic therapy, contributes to morbidity of cancer treatment, and may raise the risk of second malignancies and comorbidities. Research shows that the time after a cancer diagnosis can serve as a teachable moment to motivate individuals to adopt risk-reducing behaviors. For this reason, the oncology care team--the providers with whom a patient has the closest relationships in the critical period after a cancer diagnosis--is in a unique position to help patients lose weight and make other healthy lifestyle changes. The American Society of Clinical Oncology is committed to reducing the impact of obesity on cancer and has established a multipronged initiative to accomplish this goal by 1) increasing education and awareness of the evidence linking obesity and cancer; 2) providing tools and resources to help oncology providers address obesity with their patients; 3) building and fostering a robust research agenda to better understand the pathophysiology of energy balance alterations, evaluate the impact of behavior change on cancer outcomes, and determine the best methods to help cancer survivors make effective and useful changes in lifestyle behaviors; and 4) advocating for policy and systems change to address societal factors contributing to obesity and improve access to weight management services for patients with cancer.
Observational studies have suggested that metformin decreases the incidence of several common cancers. However, findings regarding breast cancer have been mixed. In order to explore this issue, a ...systematic literature review and meta-analysis were performed with a focus on potential biases. We conducted a comprehensive literature search for all pertinent studies addressing metformin use and breast cancer risk by searching PubMed, Cochrane Library, and Scopus (which includes Embase, ISI Web of Science) using the Mesh terms: “metformin” or “biguanides” or “diabetes mellitus, type 2/therapy” and “cancer” or “neoplasms.” When multiple hazard ratios (HR) or odds ratio (OR) were reported, the most adjusted estimate was used in the base-case analysis. We pooled the adjusted HR and performed sensitivity analyses on duration of metformin use (> or ≤3 years use), study quality (assessed using the GRADE system), and initial observation year of the cohort (before vs after 1997). From a total of 443 citations, 18 full-text articles were considered, and seven independent studies were included. All were observational (four cohort and three case control). Our combined OR of all seven studies was 0.83 (0.71–0.97). Stronger associations were found when analyses were limited to studies estimating the impact of longer metformin use (OR = 0.75. 95 % CI 0.62, 0.91) or among studies that began observing their cohort before 1997 (OR = 0.68. 95 % CI 0.55–0.084). Stratification according to study quality did not affect the combined OR but higher quality studies had smaller CI and achieved statistical significance. Interpretation is limited by the observational nature of reports and different comparison groups. Our analyses support a protective effect of metformin on breast cancer risk among postmenopausal women with diabetes. Clinical trials are needed for definitive determination of the role of metformin in breast cancer risk reduction.
Purpose Observational study evidence has associated overweight/obesity with decreased survival in women with breast cancer and with several other cancers. Although full-scale, definitive weight loss ...adjuvant intervention trials with cancer end points remain to be conducted, a number of randomized controlled trials have evaluated weight loss interventions in survivors of cancer in women. Findings from these trials in breast, endometrial, and ovarian cancer are reviewed. Methods A systematic review of randomized controlled clinical trials evaluating weight loss interventions was updated (for studies published 2013 to 2016), and clinical trials registers were searched for ongoing trials. Results Six new randomized trials in breast cancer survivors and two randomized trials in endometrial cancer survivors were identified. Evidence from these trials and the 10 earlier randomized trials in female cancer survivors provide support for the feasibility of recruiting women closer to the cancer diagnosis and efficacy for achieving weight loss, in particular with telephone-based interventions, and have identified the challenge of achieving significant weight loss in African American cancer survivors and of maintaining weight loss in any cancer survivor group. Seven ongoing randomized trials are evaluating the influence of weight loss interventions on cancer end points (five in breast cancer, one in ovarian cancer, and one in endometrial cancer). Conclusion After a decade of preliminary studies, ongoing randomized, controlled clinical trials will potentially provide definitive assessment of whether weight loss can improve breast cancer clinical outcome. Longer-term interventions (> 2 years' duration) may be needed to optimize weight loss maintenance and any potential benefits on cancer end points.
The menopausal hormone therapy (MHT) association with breast cancer has been controversial for more than 40 years. Most recently, findings from cohort studies have been discordant compared with those ...from the Women's Health Initiative (WHI) randomized trials. In cohort studies, both estrogen therapy and estrogen plus progestin were associated with higher breast cancer incidence. In contrast, in the WHI randomized trials, findings for estrogen plus progestin are concordant with cohort study reports, whereas estrogen therapy significantly reduced breast cancer incidence. In addition, concerns have been raised regarding the WHI findings from both trials. In this report, we briefly summarize findings for MHT on breast cancer from cohort studies and the WHI randomized trials. The report focus is addressing, point-by-point, concerns raised regarding the WHI findings.
For cohort studies, we relied on the latest findings from (1) the meta-analysis of the Collaborative Group on Hormonal Factors in Breast Cancer and (2) the Million Women's Study. To identify commentaries and editorials, "Menopause" and "Climacteric" were searched from 2002 to present; PubMed and Google Scholar were searched for commentaries, editorials, and breast cancer, MHT, estrogen, conjugated equine estrogen, estradiol, "hormone replacement therapy," and "HRT."
Thirty commentaries challenging WHI findings were identified. All were reviewed, and issues needing response were identified. Findings from the meta-analysis from the Collaborative Group on Hormonal Factors in Breast Cancer and the Million Women Study were summarized and compared with finding in the two WHI randomized trials evaluating estrogen therapy and estrogen plus progestin. Based on the randomized clinical trials, estrogen therapy, for women with prior hysterectomy, decreases breast cancer incidence and mortality. In contrast, estrogen plus progestin increases breast cancer incidence, which persists through two decades. Women considering estrogen plus progestin use for vasomotor symptoms should understand the breast cancer risk.
Hormone therapy is still used by millions of women for menopausal symptoms. Concerns regarding hormone therapy and breast cancer were initially based on case reports and retrospective case-control ...studies. However, recent results from large prospective cohort studies and the Women's Health Initiative (WHI) randomized placebo-controlled hormone therapy trials have substantially changed concepts regarding how estrogen alone and estrogen plus progestin influence breast cancer. The preponderance of observational studies suggested that estrogen alone and estrogen plus progestin both increased the risk of breast cancer, with cancers commonly diagnosed at an early stage. However, substantially different results emerged from the WHI randomized hormone therapy trials. In the WHI trial evaluating estrogen plus progestin in postmenopausal women with an intact uterus, combined hormone therapy statistically significantly increased the risk of breast cancer and hindered breast cancer detection, leading to delayed diagnosis and a statistically significant increase in breast cancer mortality. By contrast, estrogen alone use by postmenopausal women with prior hysterectomy in the WHI trial did not substantially interfere with breast cancer detection and statistically significantly decreased the risk of breast cancer. Differential mammography usage patterns may explain differences between observational study and randomized trial results. In clinical practice, hormone therapy users have mammograms more frequently than nonusers, leading to more and earlier stage cancer detection. By contrast, in the WHI randomized trials, mammogram frequency was protocol mandated and balanced between comparison groups. Currently, the different effects of estrogen plus progestin vs estrogen alone on breast cancer are not completely understood.
Purpose
Over the past half century, the annual age-adjusted breast cancer incidence in the USA has fluctuated, potentially influenced by changes in mammography screening, obesity, and menopausal ...hormone therapy. As the relative contributions of these factors on breast cancer incidence have not been resolved, we assembled reliable sources of year-to-year changes in mammography, obesity, and hormone therapy to graphically display their relationship to breast cancer incidence through 50 years.
Methods
Year-to-year trends were assembled: for mammography from the Center for Disease Control National Health Interviews; for hormone therapy from the Collaborative Group on Hormonal Factors in Breast Cancer report; for obesity from the NCD (Non-Communicable Diseases) Risk Factor Collaboration; and for breast cancer for US women 50–64 years of age from Surveillance, Epidemiology, and End Results (SEER) registry findings.
Results
Increases in age-adjusted breast cancer incidence trend from about 1982 to 2002 track both mammography and hormone therapy use but not obesity. However, the sudden decrease in breast cancer incidence in 2003, subsequently sustained at a lower incidence level, only tracks the parallel reduction in hormone therapy use.
Conclusion
The sustained reduction in hormone therapy use from 2003 provides a plausible explanation for most of the lower breast cancer incidence seen in US postmenopausal women during the last two decades. The strong observational study obesity association with higher breast cancer risk is not reflected in breast cancer incidence trends.
Obesity and the metabolic syndrome (MetS) have both been linked to increased risk of postmenopausal breast cancer; however, their relative contributions are poorly understood.
We examined the ...association of metabolic phenotypes of obesity defined by presence of the MetS (yes and no) and body mass index (BMI; normal, overweight, obese) with risk of postmenopausal breast cancer in a prospective analysis of a cohort of postmenopausal women (
∼ 21,000) with baseline measurements of blood glucose, triglycerides, HDL-cholesterol, blood pressure, waist circumference, and BMI. Women were classified into 6 metabolic obesity phenotypes according to their BMI (18.5-<25.0, 25.0-<30.0, ≥30.0 kg/m
) and presence of the MetS (≥3 of the following: waist circumference ≥88 cm, triglycerides ≥150 mg/dL, HDL-C <50 mg/dL, glucose ≥100 mg/dL, and systolic/diastolic blood pressure ≥130/85 mmHg or treatment for hypertension). HRs for incident breast cancer and 95% confidence intervals (95% CI) were estimated using Cox proportional hazards models.
Over 15 years of follow-up, 1,176 cases of invasive breast cancer were diagnosed. Obesity, regardless of metabolic health, was associated with increased risk of breast cancer. Being obese and metabolically unhealthy was associated with the highest risk: HR, 1.62; 95% CI, 1.33-1.96. These associations were stronger in women who had never used hormone therapy.
Our findings suggest that both obesity and metabolic dysregulation are associated with breast cancer risk.
Beyond BMI, metabolic health should be considered a clinically relevant and modifiable risk factor for breast cancer.
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