Comparison of dose-volume histograms of IMRT treatment plans for ethmoid sinus cancer computed by advanced treatment planning systems including Monte Carlo.
OBJECTIVE
To recompute clinical intensity-modulated treatment plans for ethmoid sinus cancer and to compare quantitatively the dose-volume histograms (DVHs) of the planning target volume (PTV) and the optic organs at risk.


METHODS
Ten step-and-shoot intensity-modulated treatment plans were enrolled in this study. Large natural and surgical air cavities challenged the calculation systems. Each optimized treatment plan was recalculated by two superposition convolution (TMS and Pinnacle) and a Monte Carlo system (MCDE). To compare the resulting DVHs, a one-way ANOVA for repeated measurements was performed and multiple pairwise comparisons were made.


RESULTS
The tails of the PTV-DVHs were significantly higher for the Monte Carlo system. The DVHs of the critical organs displayed some statistically but not always clinically significant differences. For the individual patients, the three planning systems sometimes reproduced clinically discrepant DVHs that were not significantly different when averaged over all patients.


CONCLUSIONS
Dose to air cavities contains computational uncertainty. As this dose is clinically irrelevant and optimizing it is meaningless, we recommended extracting the air from the PTV when constructing the PTV-DVH. The planning systems considered reproduce DVHs that are significantly different, especially in the tail region of PTV-DVHs.
Paelinck
Leen
L
Department of Radiotherapy and Nuclear Medicine, University Hospital Ghent, Gent, Belgium. Leen@krtkg1.UGent.be
Smedt
Bart De
BD
Reynaert
Nick
N
Coghe
Marc
M
Gersem
Werner De
WD
Wagter
Carlos De
CD
Vanderstraeten
Barbara
B
Thierens
Hubert
H
Neve
Wilfried De
WD
D004307:Dose-Response Relationship, Radiation; D005005:Ethmoid Sinus / Q000528:radiation effects*; D006801:Humans; D009010:Monte Carlo Method; D010255:Paranasal Sinus Neoplasms / Q000532:radiotherapy*; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated