PTV-based VMAT vs. robust IMPT for head-and-neck cancer

PTV-based VMAT vs. robust IMPT for head-and-neck cancer: A probabilistic uncertainty analysis of clinical plan evaluation with the Dutch model-based selection

Rojo-Santiago, Jesús (Erasmus MC; Holland Particle Therapy Centre)
Korevaar, Erik (University Medical Center Groningen)
Perko, Z. (TU Delft RST/Reactor Physics and Nuclear Materials)
Both, Stefan (University Medical Center Groningen)
Habraken, S.J.M. (Erasmus MC; Holland Particle Therapy Centre)
Hoogeman, M.S. (Erasmus MC; Holland Particle Therapy Centre)

2023

Background and purpose: In the Netherlands, head-and-neck cancer (HNC) patients are referred for proton therapy (PT) through model-based selection (MBS). However, treatment errors may compromise adequate CTV dose. Our aims are: (i) to derive probabilistic plan evaluation metrics on the CTV consistent with clinical metrics; (ii) to evaluate plan consistency between photon (VMAT) and proton (IMPT) planning in terms of CTV dose iso-effectiveness and (iii) to assess the robustness of the OAR doses and of the risk toxicities involved in the MBS. Materials and methods: Sixty HNC plans (30 IMPT/30 VMAT) were included. A robustness evaluation with 100,000 treatment scenarios per plan was performed using Polynomial Chaos Expansion (PCE). PCE was applied to determine scenario distributions of clinically relevant dosimetric parameters, which were compared between the 2 modalities. Finally, PCE-based probabilistic dose parameters were derived and compared to clinical PTV-based photon and voxel-wise proton evaluation metrics. Results: Probabilistic dose to near-minimum volume v = 99.8% for the CTV correlated best with clinical PTV-D_98% and VWmin-D_98%,CTV doses for VMAT and IMPT respectively. IMPT showed slightly higher nominal CTV doses, with an average increase of 0.8 GyRBE in the median of the D_99.8%,CTV distribution. Most patients qualified for IMPT through the dysphagia grade II model, for which an average NTCP gain of 10.5 percentages points (%-point) was found. For all complications, uncertainties resulted in moderate NTCP spreads lower than 3 p.p. on average for both modalities. Conclusion: Despite the differences between photon and proton planning, the comparison between PTV-based VMAT and robust IMPT is consistent. Treatment errors had a moderate impact on NTCPs, showing that the nominal plans are a good estimator to qualify patients for PT.

Head-and-neck Cancer
Intensity Modulated Proton Therapy
Polynomial Chaos Expansion
Probabilistic planning
Volumetric Modulated Arc Therapy

http://resolver.tudelft.nl/uuid:fced1fdb-7a7c-4f16-92cb-c05fb4b4e39c

https://doi.org/10.1016/j.radonc.2023.109729

0167-8140

Radiotherapy & Oncology, 186

Institutional Repository

journal article

© 2023 Jesús Rojo-Santiago, Erik Korevaar, Z. Perko, Stefan Both, S.J.M. Habraken, M.S. Hoogeman