Radiation dose escalation based on FDG-PET driven dose painting by numbers in oropharyngeal squamous cell carcinoma: a dosimetric comparison between TomoTherapy-HA and RapidArc.
OBJECTIVE
Validation of dose escalation through FDG-PET dose painting (DP) for oropharyngeal squamous cell carcinoma (SCC) requires randomized clinical trials with large sample size, potentially involving different treatment planning and delivery systems. As a first step of a joint clinical study of DP, a planning comparison was performed between Tomotherapy HiArt® (HT) and Varian RapidArc® (RA).


METHODS
The planning study was conducted on five patients with oropharyngeal SCC. Elective and therapeutic CTVs were delineated based on anatomic information, and the respective PTVs (CTVs + 4 mm) were prescribed a dose of 56 (PTV56) and 70 Gy (PTV70). A gradient-based method was used to delineate automatically the external contours of the FDG-PET volume (GTVPET). Variation of the FDG uptake within the GTVPETwas linearly converted into a prescription between 70 and 86 Gy. A dilation of the voxel-by-voxel prescription of 2.5 mm was applied to account for geometric errors in dose delivery (PTVPET). The study was divided in two planning phases aiming at maximizing target coverage (phase I) and lowering doses to OAR (phase II). A Quality-Volume Histogram (QVH) assessed conformity with the DP prescription inside the PTVPET.


RESULTS
In phase I, for both HT and RA, all plans achieved comparable target coverage for PTV56and PTV70, respecting the planning objectives. A median value of 99.9 and 97.2% of all voxels in the PTVPETreceived at least 95% of the prescribed dose for RA and HT, respectively. A median value of 0.0% and 3.7% of the voxels in the PTVPETreceived 105% or more of prescribed dose for RA and HT, respectively. In phase II, no significant differences were found in OAR sparing. Median treatment times were 13.7 min for HT and 5 min for RA.


CONCLUSIONS
Both HT and RA can generate similar dose distributions for FDG-PET based dose escalation and dose painting in oropharyngeal SCC patients.
Department of Radiation Oncology, and Center for Molecular Imaging, Oncology and Radiotherapy (MIRO), Université catholique de Louvain, Institut de Recherche Expérimentale et Clinique (IREC), Brussels, Belgium.
Sarah
S
Differding
Department of Radiation Oncology, and Center for Molecular Imaging, Oncology and Radiotherapy (MIRO), Université catholique de Louvain, Institut de Recherche Expérimentale et Clinique (IREC), Brussels, Belgium.
Edmond
E
Sterpin
Department of Oncology, Experimental Radiation Oncology, KU Leuven - University of Leuven, Leuven, Belgium.
Nicolas
N
Hermand
Department of Oncology, Experimental Radiation Oncology, KU Leuven - University of Leuven, Leuven, Belgium.
Bianca
B
Vanstraelen
Department of Oncology, Experimental Radiation Oncology, KU Leuven - University of Leuven, Leuven, Belgium.|Department of Radiation Oncology, University Hospitals Leuven, Leuven Cancer Institute, Leuven, Belgium.
Sandra
S
Nuyts
Department of Radiation Oncology, St-Luc University Hospital, Avenue Hippocrate 10, B-1200, Bruxelles, Belgium.
Nathalie
N
de Patoul
Department of Radiation Oncology, St-Luc University Hospital, Avenue Hippocrate 10, B-1200, Bruxelles, Belgium.
Jean-Marc
JM
Denis
Department of Radiation Oncology, and Center for Molecular Imaging, Oncology and Radiotherapy (MIRO), Université catholique de Louvain, Institut de Recherche Expérimentale et Clinique (IREC), Brussels, Belgium.
John Aldo
JA
Lee
Department of Radiation Oncology, and Center for Molecular Imaging, Oncology and Radiotherapy (MIRO), Université catholique de Louvain, Institut de Recherche Expérimentale et Clinique (IREC), Brussels, Belgium. vincent.gregoire@uclouvain.be.|Department of Radiation Oncology, St-Luc University Hospital, Avenue Hippocrate 10, B-1200, Bruxelles, Belgium. vincent.gregoire@uclouvain.be.
Vincent
V
Grégoire
D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D019788:Fluorodeoxyglucose F18; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D006801:Humans; D009959:Oropharyngeal Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D049268:Positron-Emission Tomography / Q000379:methods*; D011874:Radiometry / Q000379:methods; D019275:Radiopharmaceuticals; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012107:Research Design; D000077195:Squamous Cell Carcinoma of Head and Neck
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18