Multi-Target Treatment Planning and Delivery on a PET-Linac Platform : Dosimetric Robustness and Efficiency In Oligometastatic Radiotherapy
Abstract
Purpose
Treating multiple oligometastatic lesions typically requires creating separate SBRT plans, resulting in longer treatment time and an increase in planning complexity. In this work we evaluate biology-guided multi-target treatment (MTT) approach for a PET-linear accelerator where we integrate biology-guided radiotherapy (BgRT) for PET-avid lesions with image-guided radiotherapy (IGRT) for non-PET avid lesions in a single session.
Methods
Two representative clinical cases (one lung and one pelvic) were planned and analyzed using MTT and compared with separate BgRT+IGRT deliveries. Dosimetric and plan quality was evaluated using conformity index (CI), homogeneity index (HI), PTV coverage, and organ at risk (OAR) sparing. Dose volume histograms (DVHs) were reviewed for inter-target dose overlap, and total beam on time was recorded.
Results
MTT achieved comparable or improved dosimetric outcomes while reducing total delivery time by 20% to 30%. For Case 1 (dual lung lesions in different lobes), MTT was found to improved BgRT target conformity CI 1.26 vs. 1.37 and reduced treatment time by 25 %. In Case 2 (adjacent pelvic bone lesions), separate BgRT+IGRT plans resulted in over dose in the IGRT target due to cross dose from BgRT. However, the MTT plans did not have the overdose issue from the BgRT treatment as the BgRT and IGRT components of the plan were optimized simultaneously. The simultaneous optimization in MTT helped to maintain uniform dose distribution and reduce total treatment time by 22%.
Conclusion
This work shows a single MTT plan is dosimetrically feasible and clinically efficient. MTT simplifies multi-lesion SBRT, minimizes inter target dose interference, and reduces overall treatment time without compromising dosimetric quality.