将身体肥胖与乳腺癌预后联系起来的证据有限。尽管过度肥胖似乎与较差的乳腺癌生存率有关，但体重变化是否会降低死亡率存在不确定性。本研究旨在评估体脂肪和诊断前后的体重变化与乳腺癌幸存者的整体死亡率和乳腺癌特定死亡率之间的关系。我们的研究包括来自欧洲癌症与营养前瞻性调查（EPIC）研究的13,624名乳腺癌幸存者，在诊断后平均随访8.6年。对于所有病例，招募时获得了人体测量数据，并在随访期间进行了第二次评估。我们使用身体质量指数（BMI）来衡量一般性肥胖，而腰围和身体形状指数用作腹部肥胖的测量指标。对于具有两次体重评估的病例，计算了年度体重变化。与整体死亡率和乳腺癌特定死亡率的关联基于多变量Cox和Fine和Gray模型。我们进行了遗传学随机分析（MR）以研究潜在因果关系。诊断前每增加5个BMI单位与总体死亡率增加10%（95%置信区间：5-15%）和死于乳腺癌增加7%（0-15%）相关。腹部肥胖的女性整体死亡率增加23%（11-37%），独立于BMI的关联。与诊断后的体重变化相关的结果显示具有U形关系与乳腺癌特定死亡率，体重减轻或每年增加≥2%与更高的风险相关。 MR分析与确定的关联一致。我们的结果支持过度肥胖与乳腺癌女性的生存不利关联，诊断后体重变化的显著性降低可能与更差的生存率有关。©2023.作者（们）。

Evidence linking body fatness to breast cancer (BC) prognosis is limited. While it seems that excess adiposity is associated with poorer BC survival, there is uncertainty over whether weight changes reduce mortality. This study aimed to assess the association between body fatness and weight changes pre- and postdiagnosis and overall mortality and BC-specific mortality among BC survivors. Our study included 13,624 BC survivors from the European Prospective Investigation into Cancer and Nutrition (EPIC) study, with a mean follow-up of 8.6 years after diagnosis. Anthropometric data were obtained at recruitment for all cases and at a second assessment during follow-up for a subsample. We measured general obesity using the body mass index (BMI), whereas waist circumference and A Body Shape Index were used as measures of abdominal obesity. The annual weight change was calculated for cases with two weight assessments. The association with overall mortality and BC-specific mortality were based on a multivariable Cox and Fine and Gray models, respectively. We performed Mendelian randomization (MR) analysis to investigate the potential causal association. Five-unit higher BMI prediagnosis was associated with a 10% (95% confidence interval: 5-15%) increase in overall mortality and 7% (0-15%) increase in dying from BC. Women with abdominal obesity demonstrated a 23% (11-37%) increase in overall mortality, independent of the association of BMI. Results related to weight change postdiagnosis suggested a U-shaped relationship with BC-specific mortality, with higher risk associated with losing weight or gaining > 2% of the weight annually. MR analyses were consistent with the identified associations. Our results support the detrimental association of excess body fatness on the survival of women with BC. Substantial weight changes postdiagnosis may be associated with poorer survival.© 2023. The Author(s).