Potential role of intensity-modulated radiotherapy in the treatment of tumors of the maxillary sinus☆

Abstract 

To assess 3-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) techniques to see whether doses to critical structures could be reduced while maintaining planning target volume (PTV) coverage in patients receiving conventional radiotherapy (RT) for carcinoma of the maxillary sinus because of the risk of radiation-induced complications, particularly visual loss.

Six patients who had recently received conventional RT for carcinoma of the maxillary sinus were studied. Conventional RT, 3D-CRT, and step-and-shoot IMRT plans were prepared using the same 2-field arrangement. The effect of reducing the number of segments in the IMRT beams was investigated.

3D-CRT and IMRT reduced the brain and ipsilateral parotid gland doses compared with the conventional plans. IMRT reduced doses to both optic nerves; for the contralateral optic nerve, 15-segment IMRT plans delivered an average maximal dose of 56.4 Gy (range 53.9–59.3) compared with 65.7 Gy (range 65.3–65.9) and 64.2 Gy (range 61.4–65.6) for conventional RT and 3D-CRT, respectively. IMRT also gave improved PTV homogeneity and improved coverage, with an average of 8.5% (range 7.0–11.7%) of the volume receiving <95% of the prescription dose (64 Gy) compared with 14.7% (range 14.1–15.9%) and 15.1% (range 14.4–16.1%) with conventional RT and 3D-CRT, respectively. Little difference was found between the 15 and 7-segment plans, but 5 segments resulted in a reduced minimal PTV dose.

IMRT offers significant advantages over conventional RT and 3D-CRT techniques for treatment of maxillary sinus tumors. Good results can be obtained from 7 segments per beam without compromising the PTV coverage. This number of segments is practical for implementation in a busy RT department.

Keywords:  Maxillary sinus tumors, Conformal radiotherapy, Intensity-modulated radiotherapy