Single-institution clinical experience using robust intensity modulated proton therapy in chordoma and chondrosarcoma of the mobile spine and sacrum: Feasibility and need for plan adaptation

Michiel Kroesen,Vesna Miladinovic,Stefan A.J Hutschemaekers,Jenneke Jacobs,Charlotte Van Der Vos,Anne Lisa Wolf,Mischa S Hoogeman,Marco Van Vulpen,Johan L Bloem,Sander P.D.S Dijkstra,Wilco C Peul,Joan J Penninkhof,Augustinus D.G Krol

doi:10.1016/j.radonc.2021.11.020

Michiel Kroesen, Vesna Miladinovic + Show 11 more

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https://doi.org/10.1016/j.radonc.2021.11.020

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BackgroundDue to its specific physical characteristics, proton irradiation is especially suited for irradiation of chordomas and chondrosarcoma in the axial skeleton. Robust plan optimization renders the proton beam therapy more predictable upon individual setup errors. Reported experience with the planning and delivery of robustly optimized plans in chordoma and chondrosarcoma of the mobile spine and sacrum, is limited. In this study, we report on the clinical use of robustly optimized, intensity modulated proton beam therapy in these patients. MethodsWe retrospectively reviewed patient, treatment and acute toxicity data of all patients with chordoma and chondrosarcoma of the mobile spine and sacrum, treated between 1 April 2019 and 1 April 2020 at our institute. Anatomy changes during treatment were evaluated by weekly cone-beam CTs (CBCT), supplemented by scheduled control-CTs or ad-hoc control-CTs. Acute toxicity was scored weekly during treatment and at 3 months after therapy according to CTCAE 4.0. Results17 chordoma and 3 chondrosarcoma patients were included. Coverage of the high dose clinical target volume was 99.8% (range 56.1–100%) in the nominal and 80.9% (range 14.3–99.6%) in the voxel-wise minimum dose distribution. Treatment plan adaptation was needed in 5 out of 22 (22.7%) plans. Reasons for plan adaptation were either reduced tumor coverage or increased dose to the OAR. ConclusionsRobustly optimized intensity modulated proton beam therapy for chordoma and chondrosarcoma of the mobile spine is feasible. Plan adaptations due to anatomical changes were required in approximately 23 percent of treatment courses.

Highlights

Due to its specific physical characteristics, proton irradiation is especially suited for irradiation of chordomas and chondrosarcoma in the axial skeleton
The dose distribution of proton beam therapy is more sensitive to patient setup errors compared to photon therapy [13,21]
We use robustly optimized treatment plans to account for setup errors in addition to range uncertainties

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Due to its specific physical characteristics, proton irradiation is especially suited for irradiation of chordomas and chondrosarcoma in the axial skeleton. Robust plan optimization renders the proton beam therapy more predictable upon individual setup errors. Reported experience with the planning and delivery of robustly optimized plans in chordoma and chondrosarcoma of the mobile spine and sacrum, is limited. We report on the clinical use of robustly optimized, intensity modulated proton beam therapy in these patients. Methods: We retrospectively reviewed patient, treatment and acute toxicity data of all patients with chordoma and chondrosarcoma of the mobile spine and sacrum, treated between 1 April 2019 and 1 April 2020 at our institute. Reasons for plan adaptation were either reduced tumor coverage or increased dose to the OAR. Conclusions: Robustly optimized intensity modulated proton beam therapy for chordoma and chondrosarcoma of the mobile spine is feasible. Plan adaptations due to anatomical changes were required in approximately 23 percent of treatment courses.

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