2085 - ¹8F Fluciclovine PET In Postoperative Target Delineation and Recurrence Detection In Resected Brain Metastasis: Pre-Planned Analysis of a Prospective Trial
Presenter(s)
H. Hassan1, M. C. Tom2, S. Chundru3, L. Hodgson4, H. V. Vuong3, M. D. Hall1,5, R. H. Press1,5, R. P. Tolakanahalli1,5, D. J. Wieczorek1,5, Y. Lee1,5, E. Bander6,7, M. W. McDermott6,7, M. P. Mehta1,5, and R. Kotecha1,5; 1Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL, 2Department of CNS Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 3Department of Radiology, Baptist Health South Florida, Miami, FL, 4Department of Biostatistics, Miami Cancer Institute, Miami, FL, 5Department of Oncological Sciences, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 6Department of Neurosurgery, Miami Neuroscience Institute, Baptist Health South Florida, Miami, FL, 7Department of Neuroscience, Herbert Wertheim College of Medicine, Florida International University, Miami, FL
Purpose/Objective(s): MRI is used for brain metastases (BM) target volume delineation in the post-operative setting; however, it is challenging to distinguish post-operative changes from residual or recurrent disease. This pilot study assesses the role of ¹8F-fluciclovine amino acid PET/CT (fluciclovine PET), in evaluating the extent of resection and improving target volume delineation.
Materials/Methods: We performed a prespecified analysis of a prospective, single-institution trial (NCT05554302) in adults with brain metastases planned for resection and post-operative fractionated stereotactic radiosurgery (FSRS). Patients underwent a baseline planning MRI and fluciclovine PET 2–4 weeks post-resection, received 3–5 fractions of FSRS, and had follow-up MRI and fluciclovine PET imaging at 6 and 12 months. The primary endpoints were the change in target volume with fluciclovine PET, assessed by the conformality index (CI), ratio of PET–MRI intersection to union volume, and enhanced detection of local recurrence. For intact BM, Secondary endpoints included pre- and post-treatment changes in PET SUV parameters (SUVmean, SUVmax, SUVpeak) and changes in lesion volumes on MRI. Paired t tests were used to evaluate changes in MRI volume and PET SUV parameters (p < 0.05).
Results: Among ten patients (7 female, 60% lung primary) enrolled, 10 post-resection cavities and 39 intact brain metastases were evaluated with MRI and fluciclovine PET. Of the 10 resection cavities, 9 (90%) demonstrated gross total resection (GTR) and 1 (10%) had near total resection (NTR). Although median post-operative cavity volumes were identical on MRI and MRI + fluciclovine PET (8.5 cc; IQR, 5.9–17.1 vs 5.9–19.3), three patients had fluciclovine PET–informed differences, with CI values of 0.98, 0.92, and 0.70, and overall median CI of 1.00 (IQR, 0.98–1.00). At a median follow-up of 12 months (range, 0.0–12.0), post- resection cavity local control was 100.0%. All 39 intact treated lesions (median volume, 0.016 cc; range, 0.003–0.931 cc) demonstrated progressive reductions in MRI volume and fluciclovine PET–derived metabolic metrics over time. MRI volume showed a significant reduction at 6 months (median, 100%; p = 0.045) and remained 100% at 12 months, with no further significant change (p = 0.180). SUVmean, SUVmax, and SUVpeak also showed downward trends at 6 months, with median reductions of 21.9% (IQR, -11.9 to 100%), 39.7% (IQR, 6.6 to 100%), and 13.3% (IQR, -53.8 to 100%), respectively. Longitudinal analysis of 33 lesions with sufficient follow-up imaging demonstrated a significant overall decrease in SUVmax across the 12-month follow-up period (p = 0.008). No imaging agent related adverse effects were observed.
Conclusion: Post-operative PET+MRI guided FSRS was associated with excellent tumor control in this preliminary cohort. In addition, PET metrics before and after SRS for intact brain metastasis appear to demonstrate long-term changes even when anatomic MRI stability is visualized.