Sep 29

SS 30 - Radiation and Cancer Physics 4: Novel Treatment Techniques and Early Clinical Experience

275 - Clinical Outcomes of Biology-Guided Radiation Therapy for Osseous Metastases

05:20pm - 05:30pm PT

Room 154

Presenter(s)

Pule Wang, MD - City of Hope Cancer Center, Duarte, CA

P. Wang¹, Y. R. Li¹, A. Kassardjian¹, K. A. Al Feghali², D. D. Jong², C. J. Ladbury¹, A. Amini¹, Y. Liu¹, Y. J. Chen¹, S. M. Glaser¹, S. Sampath¹, C. Han¹, A. Liu¹, T. M. Williams¹, and W. T. Watkins¹; ¹Department of Radiation Oncology, City of Hope National Medical Center, Duarte, CA, ²RefleXion Medical, Inc., Hayward, CA

Purpose/Objective(s): Biology-guided radiotherapy (BgRT) is a novel external beam radiotherapy delivery modality with integration of positron emission tomography and computed tomography (PET-CT) for treatment planning and delivery. This allows for real-time tracked delivery and target adaptation with PET radiotracers; the initial FDA clearance is for Fluorodeoxyglucose (FDG)-guided treatment of lung and osseous tumors. We report on the first clinical outcomes for 10 patients treated using BgRT for osseous metastases with a medical technology company system.

Materials/Methods: The X1 system performs PET-guided delivery (SCINTIX BgRT) with daily FDG injections and real-time imaging and adaptation during treatment. We present clinical data including patient demographics, treatment sites, PET characteristics, treatment dose, plan quality indices, pain response and toxicity at follow up. Metabolic Response (MR) was categorized using the Positron Emission Tomography Response Criteria in Solid Tumors (PERCIST) including quantitative changes in standardized uptake value (SUV_mean and SUV_max).

Results: Between December 2023 and November 2024, 10 patients received BgRT for osseous metastases with median follow-up of 5.1 (range: 3.1-12.6) months, median age of 60 (52-78), and Karnofsky Performance Scale (KPS) = 70. Racial/ethnic background was 30% Hispanic, 40% non-Hispanic white, and 30% Asian. RT treatment sites included femur (n=2), ileum (n=2), rib (n=2), lumbar spine (n=2), scapula (n=1), and hip (n=1). The range of gross tumor volume (GTV) was 2.9-230.5 cc and planning target volume (PTV) was 10.8-376.3cc. Pre-BgRT SUV_mean and SUV_max ranged from 2.22-7.98 and 4.91-39.16, respectively. The median total dose to PTV was 17.5 (range:10-27) Gy delivered in 1-3 fractions with GTV dose up to 16 Gy in 1 fraction. The prescription isodose Conformity Index (CI100) was 1.31±0.19 in the ten plans. Eight (80.0%) patients had a complete pain response, and two (20.0%) patients had a partial pain response. One patient experienced grade 1 nausea, no grade = 2 toxicity was observed. Among 7 patients with post-BgRT PET-CT imaging, 3 (42.9%) patients had complete MR, 4 (57.1%) had partial MR. Following BgRT, the average decreases in SUV_mean and SUV_max were 50.4%±24.8% and 65.8%±19.2%, respectively.

Conclusion: We observed successful outcomes in patients who received SCINTIX BgRT for treatment of osseous metastases, including significant reductions in pain and PET activity with minimal toxicity. BgRT including repeated FDG imaging was well tolerated and can be utilized for a wide range of PET activity, tumor sizes and PTV-expansions of PET-active volumes.