Abstract
BackgroundTo compare non coplanar field (NCF) with coplanar field (CF) -intensity-modulated radiotherapy (IMRT) planning for ethmoid cancer.MethodsSeven patients treated with NCF IMRT for ethmoid cancer were studied. A CF IMRT optimization was prepared with the same constraints as for the NCF treatment. The maximum point doses (D max) obtained for the different optic pathway structures (OPS) should differ no more than 3% from those achieved with the NCF IMRT plan. The distribution of the dose in the target volume and in the critical structures was compared between the two techniques, as well as the Conformity (CI) and the Homogeneity Indexes (HI) in the target volume.ResultsWe noted no difference between the two techniques in the OPS for the D1, D2, and D5%, in the inner ear and controlateral lens for the average Dmax, in the temporo-mandibular joints for the average mean dose, in the cord and brainstem for the average D1%. The dose-volume histograms were slightly better with the NCF treatment plan for the planning target volume (PTV) with a marginally better HI but no impact on CI. We found a great improvement in the PTV coverage with the CF treatment plan for two patients with T4 tumors.ConclusionIMRT is one of the treatment options for ethmoid cancer. The PTV coverage is optimal without compromising the protection of the OPS. The impact of non coplanar versus coplanar set up is very slight.
Highlights
To compare non coplanar field (NCF) with coplanar field (CF) -intensity-modulated radiotherapy (IMRT) planning for ethmoid cancer
Dose distribution in the optic pathways The maximum dose in the optic chiasma, ipsilateral and controlateral optic nerves are represented in the Figure 1a,b,c
The differences did not exceed 2 Gy except for patient n° 2, where the dose in the controlateral optic nerve was more than 3 Gy lower with the CF technique
Summary
To compare non coplanar field (NCF) with coplanar field (CF) -intensity-modulated radiotherapy (IMRT) planning for ethmoid cancer. Ethmoid sinus cancers are rare malignant tumors of the paranasal sinuses They are often diagnosed at a late stage and are often, at that point, locally advanced. The dose delivered to the optic structures depended on initial staging of the pathology and was at the discretion of the physician. For all these patients, we came up with a coplanar treatment plan, with the same maximum doses to optic structures as those obtained with NCF.
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