2184 - Spacers for Proton Therapy: Space-Making Proton Therapy (SMPT)
Presenter(s)
M. Navratil1, S. Vinakurau1, V. Vondracek1, D. Klika1, J. Engelova1, P. Hladik2, B. Jisova2, O. Bradac2, R. Brabec3, and T. Hosszu4; 1Proton Therapy Center Czech s.r.o., Prague, Czech Republic, 2Motol University Hospital, Prague, Czech Republic, 3Regional Hospital Liberec, Libererc, Czech Republic, 4University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
Purpose/Objective(s): In this study was investigated the use of different spacers in radiation treatment of different types of tumors – not only prostate. Sacral chordoma and hemangioblastoma have high local aggressiveness and a high percentage of local recurrence after macroscopically radical procedures. Therefore, it is necessary to deliver a high dose to ensure a sufficient therapeutic effect. Intensity Modulated Proton Therapy (IMPT) allows the delivery of a high biologically effective dose to the tumor, while offering sparing of the surrounding organs. When the space between a tumor and the rectum or intestine is too narrow, it may be challenging to safely deliver effective radiation doses without risking organ damage. Inserting a surgical spacer before IMPT creates a safe distance around the tumor and allows better coverage of the target volume. Same principle may be used also for sparing spinal cord during e.g. chordoma irradiation. There is possible to use a polyester (PES) suture pad as a spacer between spine and tumor itself.
Materials/Methods: Between March 2021 and January 2023 were treated 5 patients with sacral tumors that were enrolled for surgical placement of a silicon spacer: four with chordoma (CH) and one with hemangioblastoma. Spacers were inserted by experienced surgeons and patients were thereafter treated with IMPT with doses of 74 GyE (37 fractions) for chordoma and 35 GyE (7 fractions) for hemangioblastoma. Four patients received first-time radiotherapy treatment, while one patient underwent radiotherapy for local recurrence following surgery and previous high-dose radiotherapy. Treatment of the first patient with the PES spacer around spine is in progress nowadays. Dosimetrical properties of both types of spacers were deeply investigated. Differences between dose distributions with and without spacers were evaluated.
Results: All five patients with SMPT are without disease progression, and none have severe toxicity. Acute toxicity was mild. Average volume of the spacer was 128.6 cm3. Depending of the tumor and spacer position was the dose reduction to bowel up to 72GyE in D1cm3.
Conclusion: Placement of a silicon spacer for SMPT to patients with primary sacral tumors is feasible and beneficial for patients. PES spacer placement around the spine is feasible.