Lisca Wurfbain, Amsterdam UMC

Purpose:
This study aims to investigate the patterns of care in patients treated for an ipsilateral breast tumor event(IBTE) with curative intent and to provide insight in three- and five-year overall survival.

Methods:
A retrospective cohort study was conducted using data from patients treated between 2016 and 2017 at 34 hospitals in the Netherlands. Data on patient- and tumor-related characteristics, locoregional, and systemic treatments were collected from electronic case report files and descriptive statistics were used to provide insight in IBTE characteristics and treatment. Three and five-year overall survival rates were evaluated using Kaplan-Meier analysis.

Results:
Of the 486 IBTE patients treated with curative intent, 75.1% were diagnosed with a IBTE within five years after the primary tumor diagnosis. Tumor receptor discordance between primary and IBTE tumors was observed in 21.1% of cases. A total of 72 (14.8%) received neoadjuvant systemic therapy for the IBTE. Salvage mastectomy was performed in 435 patients (89.5%), while 51 (10.5%) underwent repeat breast-conserving surgery (BCS). Out of the 51 patients treated with repeat BCS, 31 (60.8%) received postoperative whole-breast re-irradiation (WBI). Among those treated with salvage mastectomy, 411 (94.5%) received radiotherapy for the primary tumor, of whom 54 (13.1%) received repeat radiotherapy for IBTE, alone (24.1%) or in combination with hyperthermia (75.9%). Adjuvant systemic therapy was administered to 56.6% of patients with IBTE. A second/subsequent event occurred in 17.4% of patients, with 39.8% presenting IBTE and 49.4% distant metastasis . The 3- and 5-year survival rates were 89.0% and 72.5%, respectively.

Conclusion:
Salvage mastectomy remains the predominant treatment for IBTE, although second BCS with re-irradiation is increasingly considered for selected low-risk patients. The observed receptor discordance between primary and IBTE tumors emphasizes the need for individualized treatment. This study highlights the heterogeneity in IBTE management and underscores the necessity for more standardized guidelines.