Nasal packing does not affect the dosimetry of sinonasal cancers treated with intensity-modulated radiotherapy or volumetric-modulated arc therapy

Abstract

Introduction: To investigate the impact of nasal packing on radiotherapy dosimetry for nasal and paranasal sinus cancers treated with intensity modulate radiotherapy (IMRT) or volumetric modulated arc therapy (VMAT) technique. Methods: A prospective database identified all patients with primary nasal and paranasal sinus cancers treated with adjuvant radiotherapy. All patients were simulated using CT scanning with packing in the nasal cavity. For this study the nasal packing was contoured and assigned an electron density equivalent to air. The dose to the pre-operative gross tumour volume (GTV), planned tumour volume (PTV) and organs-at-risk (OAR) were re-calculated and compared to those with nasal packing, using both the Pinnacle (Collapsing Cone Convolution) and Monaco (Monte Carlo) planning systems. Results: 24 patients were identified, predominantly ethmoid (14) or maxillary (4) primaries. The predominant histology was SCC (12/24). The majority (22/24) were treated with curative intent. Using Collapsing Cone Convolution calculation, the median [range] coverage of 95% of prescribed dose to high-dose PTV (95.5% [92.2-98.5%] vs 95.2% [92.1-98.5%]; packing vs no packing, P=1.00) and low-dose PTV (95.8% [90.0-99.4%] vs 95.9% [91.1-99.7%]; packing vs no packing, P=1.00) were not impacted by packing the nasal cavity. There was also no impact by no packing on the maximal dose to the brainstem, optic nerves, optic chiasm nor lens. Conclusions: Packing of nasal cavity does not change the dose to the PTVs or critical OARs in patients with nasal and paranasal sinus cancers treated with adjuvant IMRT or VMAT radiotherapy and can be safely omitted.