Real-world characteristics and invasive disease-free survival of resected patients with HR-positive/HER2-negative early breast cancer: evidence from German population-based cancer registries

Background: Hormone receptor-positive (HR-positive) and human epidermal growth factor receptor 2-negative (HER2-negative) tumors are the most prevalent subtypes of early breast cancer (eBC). Despite the generally favorable prognosis, a relevant proportion experiences invasive disease events following surgery. We aimed to describe characteristics, treatment modalities, and survival outcomes of surgically treated patients with HR-positive/HER2-negative eBC in Germany. Materials and methods: This study used data from eight population-based clinical cancer registries in Germany. Patients diagnosed between 2017 and 2021 with HR-positive/HER2-negative eBC who underwent surgery within 4 months of diagnosis were included. Patient and tumor characteristics and treatment received before recurrence were described. Kaplan-Meier statistics and multivariable Cox regression were used to assess invasive disease-free survival (iDFS). Results: A total of 43 214 patients with a median follow-up time of 47 months were included. Among these, 5635 experienced an iDFS event, of which 38.0% were recurrences as the first observed event. Recurrence more often occurred among men, premenopausal women, and patients with larger tumors, greater nodal involvement, and higher tumor grade. The 5-year iDFS was 82.9% (95% confidence interval 82.4-83.3). In multivariable analysis, higher age, tumor size, nodal involvement, histologic grade, and mastectomy compared with breast-conserving surgery were associated with a lower iDFS. Conclusions: These real-world data emphasize that 83% of patients with HR-positive/HER2-negative eBC do not experience recurrence, second primary malignancy, and death within 5 years. The prognostic relevance of established tumor-related factors for iDFS was confirmed in a large unselected patient population in the German routine care setting.