ESTRO 2024 - Abstract Book

S540

Clinical - Breast

ESTRO 2024

1252

Poster Discussion

MRI contrast clearance analysis (CCA) post SRS for breast cancer: disease or radionecrosis?

Sukhdeep K Nagpal 1,2 , Anna M Kirby 1,2 , Gillian Ross 1,2 , Sumeet Hindocha 1,2 , Faraan Khan 3 , Andrew Mackinnon 3 , Philip Rich 3 , Bhupinder Sharma 2,3 1 The Royal Marsden NHS Foundation Trust, Department of Radiotherapy, London, United Kingdom. 2 The Institute of Cancer Research, Division of Radiotherapy and Imaging, London, United Kingdom. 3 The Royal Marsden NHS Foundation Trust, Department of Radiology, London, United Kingdom

Purpose/Objective:

Brain metastases develop in approximately 10-30% of breast cancer patients [1 – 3]. While systemic therapies play an important role in controlling brain metastases, local treatments with surgery and/or radiotherapy remain the mainstay of management [4]. Radionecrosis is the most common late complication of SRS and may require treatment with corticosteroids, bevacizumab or surgical resection [5,6], whereas treatment of neurological disease progression includes the possibility of re-irradiation or switching systemic anti-cancer therapy (SACT) [4]. These differing management approaches highlight the importance of distinguishing these diagnoses. Contrast-enhanced MRI is the standard imaging modality used for response assessment and surveillance post-SRS. However, conventional MRI may not reliably distinguish between treatment-related changes and active disease. Contrast Clearance Analysis (CCA) formally termed Treatment Response Assessment Maps (TRAMs) shows promise in differentiating radionecrosis from progressive disease. CCA is an MRI-based approach that requires the acquisition of T1-weighted sequences at 5 and then 60-105 minutes after contrast injection. The difference between these two images is then displayed as a colour map. Blue regions indicate rapid contrast clearance by viable tumours with intact circulation, while red regions suggest contrast accumulation due to vessel damage, potentially indicating necrotic tumour or radiation-induced brain injury [7,8]. CCA has demonstrated 100% sensitivity and a 92% positive predictive value for active disease [7]. This retrospective review aims to determine CCA’s ability to clarify equivocal findings reported on standard contrast enhanced MRI. Additionally, this study evaluates the impact of CCA on treatment decisions. To our knowledge, this study presents the largest cohort of metastatic breast cancer patients imaged with CCA post-SRS to date. Retrospective analysis of data from breast cancer patients with brain metastases who underwent CCA imaging post SRS between May 2017 and June 2023. CCAs were performed when initial standard contrast-enhanced MRI showed equivocal findings. The study received approval as a service evaluation from our institutional research committee. The proportion of patients for whom CCA identified the underlying diagnosis was recorded. CCA findings were categorised into 4 groups; 1. disease, 2. treatment-related changes (including radionecrosis), 3. mixed changes, 4. equivocal changes. Treatment recommendations made based on CCA reports were documented. Concordance between CCA reports and surgical resection histology was assessed where available. Electronic patient records were reviewed to identify eligible patients and descriptive statistics present the data. Material/Methods: