Patterns of Care and Follow-up of Patients with an Ipsilateral Breast Tumor Event After Breast-Conserving Surgery: A Multicenter Retrospective Cohort Study in the Netherlands.

Abstract

This study investigated patterns of care and oncological outcomes in patients with ipsilateral breast tumor events (IBTE) after prior breast-conserving surgery (BCS) treated with curative intent. A retrospective cohort study was conducted on IBTE patients treated in 2016-2017 at 34 Dutch hospitals. Patient and characteristics, along with treatment details were collected and descriptive statistics were used for analysis. Overall survival (OS), disease-free survival (DFS) and breast cancer-specific survival (BCSS) were evaluated by using Kaplan-Meier analyses. Of the 486 IBTE patients, 75.1% were diagnosed more than 5 years after the primary tumor, 87.4% had invasive breast cancer, and 12.6% DCIS. Distinguishing true recurrences from second primaries was not possible. Among invasive IBTE, 70 (14.6%) had primary DCIS and 350 (72.8%) an invasive primary tumor. Most IBTEs (54.9%) were T1, grade II (46.5%), and ER/PR+/HER2- (61.7%). Seventy-two (14.8%) patients received neoadjuvant systemic therapy. Salvage mastectomy was performed in 435 (89.5%) patients, while 51 (10.5%) underwent repeat BCS; 60.8% of these received postoperative whole-breast re-irradiation. Among mastectomy patients, 411 (94.5%) had prior radiotherapy; 13.1% received repeat radiotherapy, either alone (24.1%) or with hyperthermia (75.9%). Adjuvant systemic therapy was administered to 64.9%. After a median follow-up of 37 months, 83 (17.4%) developed a subsequent event: 33 (39.8%) second IBTE, 9 regional recurrences, and 41 (49.4%) distant metastases. Three- and five-year OS was 89% and 72.5%, respectively. Three- and five-year DFS was 85.5% and 69.9%, respectively. Three- and five-year BCSS was 95.1% and 86%, respectively. Salvage mastectomy was the predominant treatment for IBTE, although repeat BCS with re-irradiation is increasingly performed in selected low-risk patients. Survival outcomes were favorable. The study highlights the need for tumor re-assessment and emphasizes the variability in IBTE management, underscoring the need for standardized treatment guidelines.