Effectiveness of weight loss interventions in breast cancer survivors: a systematic review of reviews.

BACKGROUND: Elevated body mass index (BMI) in breast cancer survivors (BCS) is associated with cancer recurrence and poorer treatment response. Guidelines recommend 5%-10% weight loss for overweight or obese BCS. OBJECTIVES: To assess effectiveness of lifestyle interventions for female BCS on weight loss, BMI, body composition, health-related quality of life (HRQoL), physical functioning, psychosocial measures, biomarkers. DESIGN: Systematic review of reviews and meta-analyses. SETTING: All clinical settings. PARTICIPANTS: Adult female BCS (active treatment or post-treatment). METHODS: Medline, Embase, CINAHL, PsycINFO, Cochrane Library (including Database of Abstracts of Reviews of Effects) were searched for systematic reviews published in English between 1990 and 2022, with weight, BMI or body fat as primary outcome. Narrative reviews, editorials, letters, conference abstracts were excluded. Review quality was assessed using the Joanna Briggs Institute quality assessment tool. RESULTS: 17 reviews were included. Twelve reported significant reductions in one or more anthropometric outcomes: weight -1.36 kg (95% CI:-2.51 to -0.21) to -3.8 kg (95% CI: -5.6 to -1.9); BMI -0.89 kg/m 2 (95% CI: -0.15 to -0.28) to -3.59 kg/m 2 (95% CI: -6.29 to 0.89) or body fat -1.6% (95% CI: -2.31 to -0.88) to -2.6% (95% CI not reported). Significant reductions in two or more anthropometric outcomes were reported in 7/12 reviews, with effective interventions comprising aerobic exercise/aerobic exercise plus resistance training (n=5), or diet and exercise with or without counselling (n=2). Significant improvements were also reported for HRQoL (8/11 reviews), mental health (4/7) and physical functioning (2/3). Group interventions comprising aerobic exercise or aerobic exercise plus resistance training were most likely to improve outcomes. CONCLUSIONS: Lifestyle interventions can significantly improve outcomes for BCS. Multimodal interventions are likely to have the greatest impact in reducing weight, BMI and body fat. Further research must define the optimal combination, intensity and duration of effective interventions. PROSPERO REGISTRATION NUMBER: CRD42021283481.