Gantry-based pencil beam scanning proton therapy for uveal melanoma: IMPT versus proton arc therapy
Abstract Background This study reports the single-institution clinical experience of multifield pencil beam scanning (PBS) intensity-modulated proton therapy (IMPT) and dosimetric comparison to proton arc for uveal melanoma (UM) in a regular PBS gantry room. Methods Eleven consecutive UM patients we...
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| Main Authors: | , , , , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
BMC
2025-04-01
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| Series: | Radiation Oncology |
| Subjects: | |
| Online Access: | https://doi.org/10.1186/s13014-025-02621-y |
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| Summary: | Abstract Background This study reports the single-institution clinical experience of multifield pencil beam scanning (PBS) intensity-modulated proton therapy (IMPT) and dosimetric comparison to proton arc for uveal melanoma (UM) in a regular PBS gantry room. Methods Eleven consecutive UM patients were treated with IMPT to 50 Gy in 5 fractions. A customized gaze-fixation device attached to the thermoplastic mask was used to reproduce the globe position for each patient. IMPT plans were robustly optimized with perturbations of 3 mm setup and 3.5% range uncertainties using 3–4 fields without apertures. Each plan was robustly reoptimized (using the same perturbation parameters) using two non-coplanar arc fields in the RayStation treatment planning system. Treatment quality for both plans was evaluated daily using CBCT-generated synthetic CT. Target coverage, conformity, and mean/maximum doses to adjacent organs were assessed. Results Proton arc plans provided comparable plan quality compared to IMPT plans. Similar target coverage was achieved, with an average GTV D95% equal to 101.1% $$\:\pm\:$$ 1.0% and 101.4% $$\:\pm\:$$ 0.4% for IMPT and proton arc plans, respectively. Proton arc improves the conformity index (RTOG) compared to IMPT plans (average 0.96 $$\:\pm\:$$ 0.23 vs. 0.88 $$\:\pm\:$$ 0.18, p = 0.11). Both modalities met all the clinical goals for organs-at-risk (OARs), while proton arc significantly reduced the maximum dose for the retina from, on average, 54.5 $$\:\pm\:$$ 0.7 to 53.2 $$\:\pm\:$$ 0.3 Gy (p < 0.01). Treatment evaluation on synthetic CT showed that the doses received by patients were highly consistent with the planned doses, with a relative target coverage (D95%) difference within 3.5% for IMPT and 3.1% for proton arc, and the D95% of actual delivery exceeding 98.7% and 98.2%, respectively. The doses delivered to OARs did not exceed clinical constraints. Conclusions This is a novel report on proton arc for ocular tumors and gantry-based multifield PBS proton treatment for these tumors. This study demonstrated that both modalities can meet the clinical goals. The IMPT is currently clinically implanted, and 2-field non-coplanar proton arc plans can achieve comparable dosimetric metrics to those of IMPT plans when the deliver technique is matured. |
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| ISSN: | 1748-717X |