Helical intensity-modulated radiation therapy vs. C-arm-based volumetric modulated arc therapy for sinonasal tumours: organ at risk sparing and treatment efficiency.

BACKGROUND AND PURPOSE: Sinonasal tumours present major radiotherapy challenges because of their proximity to the optic nerves, chiasm, and brainstem. This study aimed to evaluate helical intensity-modulated radiation therapy (HIMRT) and volumetric modulated arc therapy (VMAT), including coplanar and noncoplanar approaches, by integrating plan quality and treatment efficiency.

MATERIALS AND

METHODS

A retrospective planning analysis of 467 patients with sinonasal tumours was conducted using HIMRT and VMAT planning techniques, whereby HIMRT with jaw widths of 1.0, 2.5, and 5.0 cm were compared with coplanar and noncoplanar VMAT plans. The planning evaluation included dose coverage (D95, D98, D2, D50%), homogeneity index, and dose spillage metrics (V10-V90%). Organ-at-risk doses were assessed for the optic apparatus, brainstem, and parotids. Efficiency was evaluated via monitor units and beam-on time, whereas delivery accuracy was validated via OSL dosimetry and gamma analysis.

RESULTS

Both techniques achieved conformal dose coverage and OAR sparing. While HIMRT with narrow jaws improved conformity, it required substantially longer beam-on times. The VMAT plans provided comparable coverage and OAR protection with fewer hotspots, and they delivered treatment in less time. Noncoplanar VMAT offered only minor gains. Phantom validation confirmed the dose delivery accuracy, with OSLD deviations < 5% and gamma passes rates > 97%.

CONCLUSION

While HIMRT and VMAT are both effective for sinonasal radiotherapy, VMAT offers superior efficiency with comparable plan quality. Therefore, HIMRT may be reserved for anatomically complex cases where marginal conformity benefits justify longer treatment times.