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Unconventional Dose Escalation with a Merging Treatment Technique Spot Scanning Proton Arc Therapy. Are We Ready for Such Treatment Paradigm?

X Ding*, X Li, G Liu, C Stevens, D Yan, P Kabolizadeh, William Beaumont Hospital, Royal Oak, MI


(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Prospective dose-escalation clinical trial may be limited with respect to contraindications and dose constraints on surrounding structures. Liver SBRT aims to treat hepatic metastasis in a curative intent as surgery and radiofrequency which desired a higher dose prescription. If we leave the radiobiological modeling debate alone, whether there is any limits or technical ceiling in the physical dose-escalation ? With an increased degree of freedom in the proton therapy via arc trajectory, spot-scanning proton arc (SPArc) therapy, as a merging novel treatment technique, could potentially offer an unconventional dose escalation. The study used a liver CT structure to demonstrate such capability. At meanwhile, raise a question to a society, what dose level shall we escalate to and how to prepare ourselves with such merging techniques.

A liver cancer patient with CTV 1377cc, GTV 305cc for dose escalation and the remaining healthy liver tissue 626cc. The right kidney, bowel, and duodenum were abutting the CTV which makes this case challenge in planning and dose escalation almost impossible with the convention technique such as IMPT or VMAT. In the clinical plan, 2-field IMPT were used and prescribe the dose to 50Gy in 15fx without exceeding the dose limitation of OARs. SPArc plan was generated and the GTV structure is used for dose escalation until one of the OARs reaches its limitation. GTV and CTV dose coverage were compared.

With all the dose constrains meet in the SPArc dose-escalation planning. The GTV and CTV reached mean dose 405.48Gy and 163.31Gy compared to 53.67 Gy and 53.45Gy respectively in IMPT. Besides, D99 of GTV received 100.98Gy in comparison 52.60Gy in IMPT. All the OARs met the clinical constraints.

Conclusion: : With the degree of optimization and treatment delivery freedom in the proton arc therapy, unconventional dose escalation could be achieved clinically.

Funding Support, Disclosures, and Conflict of Interest: Research funding from Ion Beam Application Xuanfeng Ding, Xiaoqiang Li, Di Yan has a patent related to particle arc therapy


Not Applicable / None Entered.


TH- External Beam- Particle/high LET therapy: Proton therapy – dose optimization

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