BackgroundTo characterize the clinical and pathological features and survival of patients with human epidermal growth factor receptor 2 (HER2)-low breast cancer in China.MethodsThe China National Cancer Center database was used to identify 1,433 metastatic breast cancer patients with HER2-negative disease diagnosed between 2005 and 2015. Clinicopathological features, survival, and prognosis information were extracted. Overall survival (OS) was estimated using the Kaplan–Meier method and compared using the log-rank test. Prognostic factors associated with OS were analyzed using Cox regression model with 95% confidence interval (95% CI).ResultsThere were 618 (43.1%) and 815 (56.9%) HER2-low and HER2-zero tumors out of 1,433 tumors, respectively. The proportion of hormone receptor (HR)-positive tumors was significantly higher in HER2-low tumors than in those with HER2-zero tumors (77.8% vs. 69.2%, p < 0.001). Patients with HER2-low tumors survived significantly longer than those with HER2-zero tumors in the overall population (48.5 months vs. 43.0 months, p = 0.004) and HR-positive subgroup (54.9 months vs. 48.1 months, p = 0.011), but not in the HR-negative subgroup (29.5 months vs. 29.9 months, p = 0.718). Multivariate regression analysis revealed that HER2-low tumors were independently associated with increased OS in HER2-negative population (HR: 0.85, 95% CI: 0.73–0.98, p = 0.026).ConclusionOur findings demonstrate that HER2-low tumors could be identified as a more distinct clinical entity from HER2-zero tumors, especially for the HR-positive subgroup. A more complex molecular landscape of HER2-low breast cancer might exist, and more precise diagnostic algorithms for HER2 testing could be investigated, thus offering new therapeutic targets for breast cancer treatment.

Evidence of an oligometastatic state in metastatic breast cancer (MBC) is relatively limited. The aim of our study was to investigate the clinical features and prognostic factors for extracranial oligometastatic breast cancer and to identify the best treatment approaches in this select population. Fifty postoperative inpatients diagnosed with extracranial oligometastatic breast cancer at the National Cancer Center in China between 2009 and 2014 were consecutively enrolled. Oligometastatic breast cancer was defined as MBC with three or fewer metastatic lesions confined to one organ; de novo Stage IV disease and local-regional recurrence were excluded. The median progression-free survival (PFS) and overall survival (OS) times were 15.2 and 78.9 months, respectively, and the 2-year PFS and 5-year OS rates were 40% and 58%, respectively. First-line treatment approach with standard systemic treatment + surgical resection for all metastatic lesions was an independent prognostic factor for prolonged PFS (hazard ratio = 0.32; 95% confidence interval [CI], 0.14-0.73; P = .006) and OS (hazard ratio = 0.35; 95% CI, 0.14-0.86; P = .022). Subgroup analysis showed that patients with a disease-free interval (DFI) ≥24 months, one metastatic lesion or the hormone receptor (HR) + subtype were more likely to get benefit from resection. Patients with oligometastatic breast cancer have a relatively good prognosis. Surgical resection for metastatic lesions could significantly improve PFS and OS. Further prospective research is warranted to confirm the results and to develop biomarkers for better patient selection.

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