Comparative evaluation of the doses received by the parotid glands as predictors of xerostomia be 3D-CRT, IMRT and VMAT irradiation techniques in local advanced nasopharynx cancer

Abstract

Xerostomia is commonly associated with the radio-chemotherapy treatment of the head and neck cancers. The risk increases with increasing doses received by the parotid. Severe xerostomia (defined as long-term salivary function of < 25% of baseline) may be avoided if at least one parotid gland receives less than 20 Gy. The combined treatment with cisplatin regarded as bringing a significant benefit in survival with concurrent radiotherapy is associated with increased risk of late toxicity. Intensity-modulated radiotherapy (IMRT) is considered the radio-therapeutic standard in the management of head and neck cancer. Purpose: to evaluate the possibility of modern techniques to reduce radiation doses to parotid glands compared to conventional 3D-CRT radiotherapy even if the parotid glands are not delineated as organs at risk (OAR) and dosimetric constraints are not applied. Methods: For 10 locally advanced nasopharyngeal cancer cases treated by radiotherapy with curative intent using 3D-CRT technique, alternative IMRT and VMAT plans were proposed without applying dosimetric constraints for parotid glands. Results: IMRT and VMAT techniques reduce the maximum dose (Dmax) and the mean dose (Dmean) for both parotid glands compared to the 3D-CRT technique. The treatment plans were comparatively analyzed in terms of doses received by both parotid glands. Conclusions: Modern radiotherapy techniques implementation can reduce the dose received by the parotids even in the absence of contouring them as organs at risk, reducing xerostomia and ensuring a better quality of life for the nasopharynx cancer radio-treated patients.