A treatment planning study of combined carbon ion-beam plus photon intensity-modulated radiotherapy. (July 2020)

• Record Type: Journal Article
• Authors: Schuppert, Christopher; Paul, Angela; Nill, Simeon; Schwahofer, Andrea; Debus, Jürgen; Sterzing, Florian
• Is Part Of: Physics and imaging in radiation oncology. Volume 15(2020)
• Page Start: 16
• Page End: 22
• Publication Date: 2020-07
• Subjects: Radiotherapy -- Combined modality therapy -- Heavy ion radiotherapy -- Radiotherapy, Intensity-modulated -- Radiotherapy planning -- Computer-assisted -- Head and neck neoplasms -- Carcinoma -- Adenoid cystic; Radiotherapy -- Periodicals; Radiation dosimetry -- Periodicals; Cancer -- Imaging -- Periodicals; Oncology -- Periodicals; 615.842
• DOI: 10.1016/j.phro.2020.06.008
• Languages: English
• ISSNs: 2405-6316

Abstract

Highlights: Carbon-photon radiotherapy requires an elaborate and time-consuming planning process. An established planning workflow includes independent optimization stages. A bias-dose strategy may yield favorable cumulative dose distributions. Follow-up studies will assess robustness and impact on tumor control. Abstract: Background and purpose: Combined photon intensity-modulated radiotherapy (IMRT) and sequential dose-escalated carbon ion beam therapy (IBT) is a technically advanced treatment option for head and neck malignancies. We proposed and evaluated an integrated planning strategy as opposed to an established and largely separated planning workflow. Materials and methods: Ten patients with representative malignancies of the head and neck region underwent combined carbon-photon radiotherapy (RT) in our facilities. Clinical plans were created according to the separated workflow with independent optimization stages for both modalities. Experimental plans incorporated the existing carbon IBT dose distribution into the optimization stage of a step-and-shoot photon IMRT (bias dose planning). Results: Cumulative dose distributions showed statistically significant differences between the two planning strategies and were predominantly in favor of the integrated approach. As such, target irradiation was generally maintained or even improved in a subset of metrics, while normal tissue sparing was widely enhanced; for instance, in the ipsilateral temporal lobe with median Dmean of −16% (p < 0.001). Maximum doses D1% (with adjustment for different fractionation) fell below thresholds for toxicity risk in a minority of instances, where they were previously exceeded. Integral dose did not differ significantly. Conclusions: Our findings indicate that combination planning of carbon-photon RT for head and neck malignancies may benefit from a proposed bias dose method, yielding favorable dose distribution characteristics and a streamlined planning workflow with fewer plan revisions. Further research is necessary to validate these observations in terms of robustness and their potential for higher tumor control.