引人注目的证据表明，白细胞线粒体DNA拷贝数（mtDNAcn）与多种恶性肿瘤的预后存在显著关联，且具有癌特异性。然而，白细胞mtDNAcn是否能够预测乳腺癌（BC）患者的临床结果尚未得到很好的研究。 本研究使用多重荧光竞争PCR原理的Multiplex AccuCopy™Kit测量661名BC患者外周血白细胞的mtDNA拷贝数。应用Kaplan-Meier曲线和Cox比例风险回归模型研究mtDNAcn与患者的浸润性无病生存期（iDFS）、远处无病生存期（DDFS）、乳腺癌专门生存期（BCSS）和总生存期（OS）的关系。 Cox比例风险回归模型还评估了可能的mtDNAcn-环境交互作用。白细胞mtDNA-CN较高的BC患者iDFS显著更差（5年iDFS：全面调整模型：HR = 1.433 [95％CI 1.038-1.978]，P = 0.028）。交互分析表明mtDNAcn与激素受体状态显著相关（调整后P值为相互作用：5年BCSS：0.028，5年OS：0.022），因此进一步分析主要在HR亚组中进行。多变量Cox回归分析表明，mtDNAcn是HR阳性患者BCSS和OS的独立预后因素（HR +：5年BCSS：调整HR（aHR）= 2.340 [95％CI 1.163-4.708]，P = 0.017和5年OS：aHR = 2.446 [95％CI 1.218-4.913]，P = 0.011）。本研究首次表明，白细胞mtDNA拷贝数可能会影响乳腺癌早期患者的预后结果，具体取决于中国女性的内在肿瘤亚型。©2023作者。

Compelling evidence has indicated a significant association between leukocyte mitochondrial DNA copy number (mtDNAcn) and prognosis of several malignancies in a cancer-specific manner. However, whether leukocyte mtDNAcn can predict the clinical outcome of breast cancer (BC) patients has not been well investigated.The mtDNA copy number of peripheral blood leukocytes from 661 BC patients was measured using a Multiplex AccuCopy™Kit based on a multiplex fluorescence competitive PCR principle. Kaplan-Meier curves and Cox proportional hazards regression model were applied to investigate the association of mtDNAcn with invasive disease-free survival (iDFS), distant disease-free survival (DDFS), breast cancer special survival (BCSS), and overall survival (OS) of patients. The possible mtDNAcn-environment interactions were also evaluated by the Cox proportional hazard regression models.BC patients with higher leukocyte mtDNA-CN exhibited a significantly worse iDFS than those with lower leukocyte mtDNAcn (5-year iDFS: fully-adjusted model: HR = 1.433[95%CI 1.038-1.978], P = 0.028). Interaction analyses showed that mtDNAcn was significantly associated with hormone receptor status (adjusted p for interaction: 5-year BCSS: 0.028, 5-year OS: 0.022), so further analysis was mainly in the HR subgroup. Multivariate Cox regression analysis demonstrated that mtDNAcn was an independent prognostic factor for both BCSS and OS in HR-positive patients (HR+: 5-year BCSS: adjusted HR (aHR) = 2.340[95% CI 1.163-4.708], P = 0.017 and 5-year OS: aHR = 2.446 [95% CI 1.218-4.913], P = 0.011).For the first time, our study demonstrated that leukocyte mtDNA copy number might influence the outcome of early-stage breast cancer patients depending on intrinsic tumor subtypes in Chinese women.© 2023. The Author(s).