PURPOSE Although controversial, obesity and underweight may have a negative impact on breast cancer outcome. However, the relationship between body mass index (BMI) and breast cancer outcomes according to tumor subtype and menopausal status remains unclear. METHODS This study investigated the association between BMI and breast cancer outcome in stage I-III breast cancer patients. The relationships were further evaluated according to tumor subtype and menopausal status. RESULTS A total of 5919 patients, 3475 (58.7%) hormone receptor (HR)(+) human epidermal growth factor receptor 2 (HER2)(-), 608 (10.3%) HR(+)HER2(+), 621 (10.5%) HR(-)HER2(+), and 1079 (18.2%) HR(-)HER2(-) were included. Underweight and obesity had a negative impact on relapse-free survival but did not affect overall survival. Importantly, the prognostic role of BMI was different according to tumor subtype and menopausal status. In HR(+)HER2(-) patients, underweight was associated with poor relapse-free survival and overall survival in pre-menopausal women. In contrast, obesity had negative impact on relapse-free survival and overall survival in HR(+)HER2(-) post-menopausal patients. Underweight may have a negative prognostic role in HR(+)HER2(+) patients. However, BMI did not impact the outcome of HR(-)HER2(+) and HR(-)HER2(-) patients. CONCLUSIONS The impact of BMI on breast cancer outcome was dependent on tumor subtype and menopausal status. In HR(+)HER2(-) patients, underweight and obesity had a negative prognostic role in pre-menopausal and post-menopausal women, respectively. These findings in Asian population should be further evaluated and compared in Western population.

中文翻译：

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体重指数对乳腺癌患者的预后作用因绝经状态和肿瘤亚型而异。

目的尽管存在争议，但肥胖和体重过轻可能会对乳腺癌的预后产生负面影响。然而，根据肿瘤亚型和绝经状态，体重指数（BMI）与乳腺癌结局之间的关系仍不清楚。方法本研究调查了I-III期乳腺癌患者的BMI与乳腺癌结局之间的关系。根据肿瘤亚型和绝经状态进一步评估了这种关系。结果共有5919名患者，其中3475（58.7％）激素受体（HR）（+）人表皮生长因子受体2（HER2）（-），608（10.3％）HR（+）HER2（+），621（10.5）包括HR（-）HER2（+）和1079（18.2％）HR（-）HER2（-）。体重过轻和肥胖对无复发生存有负面影响，但并不影响整体生存。重要的，BMI的预后作用因肿瘤亚型和绝经状态而异。在HR（+）HER2（-）患者中，体重不足与绝经前妇女的无复发生存率差和总体生存率有关。相比之下，肥胖对绝经后HR（+）HER2（-）患者的无复发生存和总体生存有负面影响。体重过轻对HR（+）HER2（+）患者可能具有负面的预后作用。但是，BMI不会影响HR（-）HER2（+）和HR（-）HER2（-）患者的结局。结论BMI对乳腺癌结局的影响取决于肿瘤亚型和更年期状态。在HR（+）HER2（-）患者中，体重过轻和肥胖对绝经前和绝经后女性分别具有负面的预后作用。这些在亚洲人群中的发现应进一步评估，并在西方人群中进行比较。