Room: ePoster Forums
Purpose: To exploit the potential clinical benefit of using a novel treatment technique, spot-scanning proton arc (SPArc) therapy for multiple lung metastasis treatment.
Methods: Three lung metastasis patients were selected in this study which represented three different multi-metastasis scenarios: bilateral, left or right lung. Intensity Modulated Proton Therapy (IMPT) based on the single field optimization technique and SPArc plans were generated in the three cases with a robust optimization parameter of Â±3.5% range and 5mm setup uncertainties. 6000cGy relative biological effectiveness [RBE] was prescribed to target in 30 fractions. Dose Volume Histogram (DVHs),dosimetric metrics of the organ at risk (OARs) , the probability of radiation induced pneumonitis, and treatment delivery time were compared between the SPArc and IMPT.
Results: With a similar robust target coverage, SPArc is capable of sparing OARs better compared to IMPT. More specially, SPArc reduced the Dmean of bilateral lung from 290 cGy [RBE] to 261 cGy [RBE] for patient #1 (left lung), from 897 cGy [RBE] to 735 cGy [RBE] for patient #2 (right lung), and from 1492 cGy [RBE] to 1171 cGy [RBE] for patient #3 (bilateral lungs). Based on the normal tissue complicated probability(NTCP) model, SPArc could reduce the radiation pneumonitis rate from 1.4% to 1.3%, from 4.4% to 3.3% and from 11.1% to 6.9% respectively.The proton therapy estimated delivery time depends on the energy layer switch time (ELST) where SPArc could achieve the comparable deliver efficient compared to IMPT when the ELST is less than 0.5 second.
Conclusion: SPArc could be implemented into the proton clinic to further reduce the probability of radiation induced pneumonitis for multiple lung metastasis patients than IMPT where the bilateral lung metastatic patients showed most potential benefits from this novel treatment technique.
Funding Support, Disclosures, and Conflict of Interest: Grant/Research Support: Beaumont Herb and Betty Fisher research seed grant award; Ion Beaumont Application Inc. (IBA) research funding; A patent related to the proton arc therapy is licensed to Ion Beaumont Application Inc.