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It is important to clarify the associations between modifiable lifestyle factors such as physical activity and breast cancer prognosis to enable the development of evidence-based survivorship recommendations. We performed a systematic review and meta-analyses to summarise the evidence on the relationship between postbreast cancer diagnosis physical activity and mortality, recurrence and second primary cancers. We searched PubMed and Embase through 31st October 2021 and included 20 observational studies and three follow-up observational analyses of patients enrolled in clinical trials. In linear dose-response meta-analysis of the observational studies, each 10-unit increase in metabolic equivalent of task (MET)-h/week higher recreational physical activity was associated with 15% and 14% lower risk of all-cause (95% confidence interval [CI]: 8%-22%, studies = 12, deaths = 3670) and breast cancer-specific mortality (95% CI: 4%-23%, studies = 11, deaths = 1632), respectively. Recreational physical activity was not associated with breast cancer recurrence (HR = 0.97, 95% CI: 0.91-1.05, studies = 6, deaths = 1705). Nonlinear dose-response meta-analyses indicated 48% lower all-cause and 38% lower breast cancer-specific mortality with increasing recreational physical activity up to 20 MET-h/week, but little further reduction in risk at higher levels. Predefined subgroup analyses across strata of body mass index, hormone receptors, adjustment for confounders, number of deaths, menopause and physical activity intensities were consistent in direction and magnitude to the main analyses. Considering the methodological limitations of the included studies, the independent Expert Panel concluded ‘limited-suggestive’ likelihood of causality for an association between recreational physical activity and lower risk of all-cause and breast cancer-specific mortality.

Based on the Global Cancer Update Programme, formally known as the World Cancer Research Fund/American Institute for Cancer Research Continuous Update Project, we performed systematic reviews and meta-analyses to investigate the association of postdiagnosis body fatness, physical activity and dietary factors with breast cancer prognosis. We searched PubMed and Embase for randomised controlled trials and longitudinal observational studies from inception to 31 October 2021. We calculated summary relative risks (RRs) and 95% confidence intervals (CIs) using random-effects meta-analyses. An independent Expert Panel graded the quality of evidence according to predefined criteria. The evidence on postdiagnosis body fatness and higher all-cause mortality (RR per 5 kg/m2 in body mass index: 1.07, 95% CI: 1.05-1.10), breast cancer-specific mortality (RR: 1.10, 95% CI: 1.06-1.14) and second primary breast cancer (RR: 1.14, 95% CI: 1.04-1.26) was graded as strong (likelihood of causality: probable). The evidence for body fatness and breast cancer recurrence and other nonbreast cancer-related mortality was graded as limited (likelihood of causality: limited-suggestive). The evidence on recreational physical activity and lower risk of all-cause (RR per 10 metabolic equivalent of task-hour/week: 0.85, 95% CI: 0.78-0.92) and breast cancer-specific mortality (RR: 0.86, 95% CI: 0.77-0.96) was judged as limited-suggestive. Data on dietary factors was limited, and no conclusions could be reached except for healthy dietary patterns, isoflavone and dietary fibre intake and serum 25(OH)D concentrations that were graded with limited-suggestive evidence for lower risk of the examined outcomes. Our results encourage the development of lifestyle recommendations for breast cancer patients to avoid obesity and be physically active.

IntroductionGlobally, over 1.97 billion adults and 338 million children and adolescents are living with overweight and obesity, increasing the risk of numerous co-morbidities, including at least 12 cancers(1). WCRF/AICR conducted a literature review of diet and physical activity as determinants of weight gain, overweight and obesity in adults and children. We also introduce a novel evidence-based policy framework for promoting physical activity, and linked database, currently in development as part of the EU-funded CO-CREATE project on child and adolescent obesity prevention.Materials and MethodsEvidence on diet and physical activity as determinants and risk of weight gain, overweight and obesity was systematically extracted from existing reviews and a systematic search for recent meta-analyses, then collated and analysed. The WCRF Continuous Update Project Expert Panel drew conclusions about which exposures influence risk of weight gain, overweight and obesity, using pre-defined criteria that included evidence of biological plausibility.ResultsThe Panel identified strong evidence that several diet and physical activity related exposures influence the risk of weight gain, overweight and obesity in adults and children (see table 1). Separate conclusions were drawn for adults and children in relation to screen time, considered a marker of sedentary time.However, the Panel noted that as exposures tend to cluster, physiologically interact and share common biological mechanisms, they should not be regarded as absolutely ‘singular'but an integrated concept of interrelated exposures within a pattern of lifestyle. Table 1.Risk of weight gain, overweight and obesitySTRONG EVIDENCEDECREASES RISKINCREASES RISKCONVINCINGWalkingScreen time (children)Sugar sweetened drinksPROBABLEAerobic physical activityFoods containing dietary fibre‘Mediterranean type’ dietary patternHaving been breastfedScreen time (adults)‘Fast foods’‘Western type’ dietFor full list of footnotes, see Energy Balance and Body Fatness report(1).DiscussionHealthy dietary patterns help prevent excess weight gain. Achieving such patterns requires attention to the broader economic, environmental and social factors that influence and constrain people's behaviour. The findings of this report support the need for evidence-based public health policy to help create health-enabling environments, particularly for children and adolescents. The WCRF International MOVING framework(2) presents a package of policies to promote physical activity, which alongside wider public health policy can help address the multiple drivers of overweight and obesity.

Introduction Understanding the causes of cancer depends on synthesising epidemiological, clinical and mechanistic evidence. Using this approach, the 2007 WCRF/AICR Expert Report defined the likely causal contributions of factors related to food, nutrition and physical activity to cancer risk, based on systematic literature reviews (SLRs) of evidence published up to 2005. For the Continuous Update Project (CUP) a team at Imperial College London (ICL) updates the previous databases as new studies are published. Methods The CUP follows a similar process to the 2007 Expert Report. Having first combined the separate databases for the 17 cancers reviewed for the 2007 Expert Report into one database, the ICL team conducts SLRs of links between food, nutrition physical activity and specific cancer sites, and displays and analyses the evidence according to peer-reviewed protocols. An independent expert panel draws conclusions based on the updated evidence. The database is currently being updated with papers published since 2005 through a rolling programme. A complete, continuously updated database is expected by 2015. Results An updated SLR for breast cancer was consistent with the conclusions of the 2007 Expert Report. Further reports of updated SLRs will be published on other cancers. Once the SLRs for all the cancer sites have been updated, the database will be made publicly available, and the 2007 Expert Report recommendations reviewed. Conclusion The CUP will provide a unique resource synthesising epidemiological and other evidence on food, nutrition, physical activity and cancer, to facilitate related research, and underpin advice to public and policy-makers.