2025 - Feasibility of Combining Same-Day Biology-Guided Radiotherapy (BgRT) and Stereotactic Body Radiotherapy for Patients with Oligometastatic Disease on a PET-Linac Platform
Presenter(s)
B. Cai1, C. S. Lin2, C. Shen1, T. Banks1, R. Prasad2, A. R. Godley3, G. Bal4, T. Dan1, K. D. Westover1, A. Garant1, O. K. Öz5, R. D. Timmerman1, and S. N. Badiyan1; 1Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX, 2University of Texas Southwestern Medical Center, Dallas, TX, 3Medical Artificial Intelligence and Automation (MAIA) Lab, Dallas, TX, 4RefleXion Medical, Inc., Hayward, CA, 5University of Texas Southwestern Department of Radiation Oncology, Dallas, TX
Purpose/Objective(s): BgRT employs positron emission tomography (PET) signals from the tumor to precisely guide external beam radiation to the functional target in real time. However, in oligometastic cancer settings, not all targets are PET avid. Consequently, patients with oligometastatic cancer often require concurrent SBRT and BgRT, a dual-technique, that burdens clinical workflow and increases the frequency of patient visits. In this study, we proposed a multi-target treatment (MTT) technique, that jointly optimizes BgRT and SBRT in a single treatment plan thereby enabling the simultaneous treatment of multiple targets to enhance the treatment efficiency and patient convenience.
Materials/Methods: A patient with three lung tumors, including one PET-avid target, was treated using the MTT approach that integrates BgRT and SBRT in a single MTT plan, in combination with a separate SBRT plan. In the right lung, the PET-avid tumor was treated using BgRT while an adjacent non-PET-avid tumor was treated with SBRT as part of the MTT plan. Additionally, a separate non-PET-avid tumor in the left lung was treated with an independent SBRT in the same day. The MTT plan in the right lung employed a single isocenter, whereas a distinct isocenter was used for the left lung SBRT plan. Each tumor received a total dose of 55 Gy delivered in 5 fractions. Key quantitative metrics, including PET uptake values Activity Concentration (AC), normalized target signal (NTS), target to background ratio (TBR), net PTV fraction (nPTVf), net PTV fraction ratio (nPTVfr) and mean Activity Concentration in the BTZ (BTZmAC), were calculated. For functional modeling (FM) and each treatment fraction commenced with approximately 15 mCi FDG, followed by 60 minutes uptake period to ensure adequate FDG activity for precise delivery. To minimize the patient’s time the hospital, the SBRT treatment for the left lung was administrated during the initial 45 minutes of the uptake period, followed by the BgRT treatment and concluding with the SBRT treatment to the tumors in the right lung.
Results: The PET uptake metrics obtained from FM and 5 fractions of treatment were as follows: AC = 23.91±2.55 kBq/ml, NTS = 9.62±1.16, TBR = 5.46±0.49 and BTZmAC = 18.54±4.47. Additionally, the net PTV fraction ratio (nPTVfr) = 1.0±0.05, and the net PTVfraction nPTVf = 0.61. The treatment duration were 11 minutes for the left lung SBRT, 33 minutes for the right lung BgRT, and 10 minutes for the right lung SBRT.
Conclusion: This study represents first clinical application of MTT with three targets (integrating BgRT and SBRT) in a single plan, supplemented by an additional SBRT treatment delivered during the same treatment session. By optimizing the workflow, specifically administering an SBRT treatment during the PET uptake period, this approach has the potential to significantly reduce the total time that patients with oligometastatic cancer spend in the hospital.