Interaction between body mass index and hormone-receptor status as a prognostic factor in lymph-node-positive breast cancer

The aim of this study was to determine the relationship between the body mass index (BMI) at a breast cancer diagnosis and various factors including the hormone-receptor, menopause, and lymph-node status, and identify if there is a specific patient subgroup for which the BMI has an effect on the breast cancer prognosis. We retrospectively analyzed the data of 8,742 patients with non-metastatic invasive breast cancer from the research database of Asan Medical Center. The overall survival (OS) and breast-cancer-specific survival (BCSS) outcomes were compared among BMI groups using the Kaplan-Meier method and Cox proportional-hazards regression models with an interaction term. There was a significant interaction between BMI and hormone-receptor status for the OS (P = 0.029), and BCSS (P = 0.013) in lymph-node-positive breast cancers. Obesity in hormone-receptor-positive breast cancer showed a poorer OS (adjusted hazard ratio [HR] = 1.51, 95% confidence interval [CI] = 0.92 to 2.48) and significantly poorer BCSS (HR = 1.80, 95% CI = 1.08 to 2.99). In contrast, a high BMI in hormone-receptor-negative breast cancer revealed a better OS (HR = 0.44, 95% CI = 0.16 to 1.19) and BCSS (HR = 0.53, 95% CI = 0.19 to 1.44). Being underweight (BMI 2) with hormone-receptor-negative breast cancer was associated with a significantly worse OS (HR = 1.98, 95% CI = 1.00–3.95) and BCSS (HR = 2.24, 95% CI = 1.12–4.47). There was no significant interaction found between the BMI and hormone-receptor status in the lymph-node-negative setting, and BMI did not interact with the menopause status in any subgroup. In conclusion, BMI interacts with the hormone-receptor status in a lymph-node-positive setting, thereby playing a role in the prognosis of breast cancer.本研究旨在明确乳腺癌诊断时的体重指数（body mass index, BMI）与激素受体状态、绝经状态、淋巴结状态等多种因素的关联，并识别BMI对乳腺癌预后存在影响的特定患者亚群。我们从峨山医学中心（Asan Medical Center）的研究数据库中，回顾性分析了8742例非转移性浸润性乳腺癌患者的临床数据。采用Kaplan-Meier法及引入交互项的Cox比例风险回归模型，对比不同BMI组的总生存期（overall survival, OS）与乳腺癌特异性生存期（breast-cancer-specific survival, BCSS）结局。在淋巴结阳性乳腺癌患者中，BMI与激素受体状态对OS（P=0.029）及BCSS（P=0.013）存在显著交互作用。激素受体阳性乳腺癌患者合并肥胖时，其OS表现更差（校正后风险比[hazard ratio, HR]=1.51，95%置信区间[confidence interval, CI]=0.92~2.48），BCSS亦显著更差（HR=1.80，95%CI=1.08~2.99）。与之相反，激素受体阴性乳腺癌患者的高BMI则对应更佳的OS（HR=0.44，95%CI=0.16~1.19）与BCSS（HR=0.53，95%CI=0.19~1.44）。激素受体阴性乳腺癌合并体重过低（BMI 2）患者的OS（HR=1.98，95%CI=1.00~3.95）与BCSS（HR=2.24，95%CI=1.12~4.47）均显著更差。在淋巴结阴性患者中，未发现BMI与激素受体状态存在显著交互作用，且BMI与绝经状态在任何亚群中均无交互效应。综上，在淋巴结阳性患者中，BMI与激素受体状态存在交互作用，进而对乳腺癌预后产生影响。