(P 414) PATTERNS OF RELAPSE OF BORDERLINE AND MALIGNANT PHYLLODES TUMOUR- RESULTS FROM SARCOMA REFERENCE CENTRE (SRC)

Objective: Phyllodes tumours (PT) are a rare fibroepithelial breast neoplasm. Borderline and malignant Phyllodes are considered more aggressive in nature. NCCN Guidelines recommend local surgical resection with at least a 1cm tumour-free margin as the mainstay of treatment, however this may not be achievable with breast conserving surgery and consider 5mm clearance with radiotherapy considered in selected cases. We present our 25 year experience.

Methods: Patients were retrospectively identified with a borderline and malignant PT diagnosis referred and discussed at a SRC between 2000 and 2024. Patient characteristics, surgical, pathological details, adjuvant treatment and patterns of relapse were analysed. Routine surveillance programme consisted of breast ultrasound and CXR 3-4 monthly Years 1-2, 6 monthly Years 3-5 and annually Years 6-10.

Results: 185 patients with a median follow up of 16.9 months received recommendations through a SRC. Nineteen patients (10%) previously presented with benign phyllodes. Demographic and treatment details are listed in Table1. The local recurrence rate was 15% and distant relapse rate at 14%. Median time to local recurrence occurred within 12 (2.9-49.4) months of first presentation. Nineteen patients (10%) developed local recurrence alone, 9 (5%) developed local and distant relapse and 17 (9%) patients developed metastatic disease alone. Median survival following presentation of metastatic disease is poor at 3.4 months, despite doxorubicin based chemotherapy.

Conclusion: Local control rates of 85-90% can be achieved with surgery with a minimum of 5mm clearance and/or addition of adjuvant radiotherapy. 14% develop distant metastases with poor outcomes, alternative novel systemic therapy options need to be considered to improve survival.

Summary of patient characteristics and treatments