ESTRO 2024 - Abstract Book

S760

Clinical - CNS

ESTRO 2024

treatment (both stages) and five (n=5; 6 tumors) completed the entire SSRS and the 3 complete MRI + PET/CT imaging.

Results:

Thirteen patients were included in this study and 2 were excluded because they did not undergo baseline imaging. Eleven patients treated with SSRS for thirteen protocol-eligible target lesions, and an additional 30 bystander lesions (<2 cm maximal diameter) treated with single fraction SRS (not SSRS) are evaluable. The median age was 73 years and 54% were female. Primary histologies included NSCLC (n=7), SCLC (n=2), urothelial (n=1), melanoma (n=1), breast carcinoma (n=1), and endometrial adenocarcinoma (n=1). All lesions > 5 mm exhibited baseline increase in 18F-fluciclovine uptake compared to normal contralateral uninvolved brain. The median baseline staged target lesion maximum diameter and volumes were 21.1 mm (Range [R]: 15.7-29) and 6.54cc (R: 2.37-8.12), respectively. The median baseline SUVmax, SUVpeak, and SUVmean values were 6.54 (R: 2.16-13.09), 4 (R: 1.22-7.6), and 1.96 (R: 0.5-6.2), respectively. The median relative change in maximum diameter and volume were -6.64% (Range: -33.81 to 64.55%) and -8.56% (-52.32 to 145.19%), respectively at the second scans (prior to the second SSRS procedure), and - 21.56% (R: -67.27 to 13.33% to) and -33.91% R: (-87.52 to 37.54%), respectively, at the third scans obtained at the first follow-up after completing both SSRS fractions. Corresponding median relative change values for SUVmax, SUVpeak, and SUVmean at the second scan scan were -18.85% (R: -87.35 to 173.15%), -8.53% (R: -61.85 to 99.34%), and -36.61% (R: -89.82 to 36.00%), and at the third scan -51.76% (R: -100 to 21.07%), -67.30% (R: -100 to 10.81%), and -53.30% (R: -100 to 44.29%), respectively. Bystander lesions (< 2 cm) treated with SRS had median lesion sizes and volumes of 5.25 mm (R: 2 to 17 mm), and 0.26 cc (R: 0.02 to 2.72 cc). Corresponding median relative changes for maximum diameter and volumes were -20% and -45.89% at second, and -85.19% and -87.34%, respectively at third scans. The median relative changes SUVmax, SUVpeak and SUVmean were -74.93%, -45.28%, -27.14% at the second scan, respectively, and a -100% median change for all SUV parameter at the third scan.