Patterns of Recurrence after Breast-Conserving Treatment for Early Stage Breast Cancer by Molecular Subtype

PURPOSE: To study clinical features and patterns of recurrence after breast-conserving treatment (BCT) for three molecular subtypes of early stage breast cancer. METHODS: The sample studied included 596 patients with T1-2N0-1 breast cancer who received BCT. Three groups were defined by receptor status. Luminal: estrogen receptor (ER) or progesterone receptor (PR) positive; triple negative (TN): ER, PR, and epidermal growth factor receptor-2 (HER2) receptor negative; and HER2 overexpressing: ER and PR negative but HER2 receptor positive. RESULTS: The number of patients in each group was 408 (68.5%), 105 (17.6%), and 83 (13.9%), respectively. The median follow-up period was 79 months. The TN and HER2 subtypes occurred in younger patients (p=0.0007) and had higher nuclear grade and poorer histologic grade (p<0.0001 and 0.0071, respectively). During the follow-up period, locoregional recurrence was detected as the first site of recurrence in 26 (6.4%), 11 (10.5%), and 9 (10.8%) patients in the luminal, TN, and HER2 subtypes, respectively (p=0.1924). Thirty-one (7.6%), 7 (6.7%), and 7 (8.4%) patients in each group had distant metastases as the first sign of recurrence (p=0.8996). Median time to locoregional and distant recurrence was shorter in the HER2 subtype (p=0.0889 and 0.0780, respectively), and the HER2 subtype was significantly associated with poor overall survival (p=0.0009). CONCLUSION: After BCT in Korean women with early stage breast cancer, the patterns of recurrence were not different among the molecular subtypes, although the TN and HER2 subtypes were associated with younger age, higher nuclear grade, and poorer histologic grade.