Comparison of three-dimensional vs. conventional radiotherapy in saving optic tract in paranasal sinus tumors.
OBJECTIVE
To assess the possibility of delivering a homogeneous irradiation with respect to maximal tolerated dose to the optic pathway for paranasal sinus (PNS) tumors.


METHODS
Treatment planning with conformal three-dimensional (3D) and conventional two-dimensional (2D) was done on CT scans of 20 patients who had early or advanced PNS tumors. Four cases had been previously irradiated. Dose-volume histograms (DVH) for the planning target volume (PTV) and the visual pathway including globes, chiasma and optic nerves were compared between the 2 treatment plannings.


RESULTS
The area under curve (AUC) in the DVH of the globes on the same side and contralateral side of tumor involvement was significantly higher in 2D planning (p <0.05), which caused higher integral dose to both globes. Also, the AUC in the DVH of chiasma was higher in 2D treatment planning (p=0.002). The integral dose to the contralateral optic nerve was significantly lower with 3D planning (p=0.007), but there was no significant difference for the optic nerve which was on the same side of tumor involvement (p >0.05). The AUC in the DVH of PTV was not significant (201.1 + or - 16.23 mm(3) in 2D planning vs. 201.15 + or - 15.09 mm(3) in 3D planning). The volume of PTV which received 90% of the prescribed dose was 96.9 + or - 4.41 cm(3) in 2D planning and 97.2 + or - 2.61 cm(3) in 3D planning (p >0.05).


CONCLUSIONS
3D conformal radiotherapy (RT) for PNS tumors enables the delivery of radiation to the tumor with respect to critical organs with a lower toxicity to the optic pathway.
Kamian
S
S
Department of Radiation Oncology, Cancer Research Center, Tehran University of Medical Sciences, Tehran, Iran. skamian@aeoi.org.ir
Kazemian
A
A
Esfahani
M
M
Mohammadi
E
E
Aghili
M
M
D000293:Adolescent; D000328:Adult; D000368:Aged; D019540:Area Under Curve; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009897:Optic Chiasm / Q000528:radiation effects; D009900:Optic Nerve / Q000528:radiation effects; D010255:Paranasal Sinus Neoplasms / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D020266:Radiotherapy, Conformal / Q000009:adverse effects; D012189:Retrospective Studies