Selective partial salivary glands sparing duringintensity-modulated radiation therapy fornasopharyngeal carcinoma

Objective This study evaluated the dosimetdc consequences of selective partial salivary gland sparingduring intensity-modulated radiotherapy （IMRT） for patients with nasopharyngeal carcinoma （NPC）.Methods Ten patients with NPC were enrolled in the study. Two IMRT plans were produced for eachpatient： conventional （control） and partial salivary glands-sparing （treatment）, with dose constraints to theentire parotid glands or partial salivary glands （including the parotid and submandibular glands, delineatedwith the adjacent distance of at least 0.5 cm between the glands and PTV, the planning target volume） inplanning, respectively. Dosimetric parameters were compared between the two plans, including the V110%,V100%, V95% （the volume covered by more than 110%, 100%, or 95% of the prescribed dose）, Dmin （theminimum dose） of PTV, homogeneity index （HI）, conformity index （CI）, and the mean dose and percentageof the volume receiving 30 Gy or more （V30） for the paroUd glands and submandibular glands.Results Treatment plans had significantly lower mean doses and V30 to both the entire parotid glandsand partial parotid glands than those in control plans. The mean doses to the partial submandibular glandswere also significantly lower in treatment plans than in control plans. The PTV coverage was comparablebetween the two plans, as indicated by V100%, V95%, Dmin, CI, and HI. The doses to critical structures, includingbrainstem and spinal cord, were slightly but not significantly higher in treatment plans than in control plans.Conclusion A selective partial salivary gland-sparing approach reduces the doses to parotid andsubmandibular glands during IMRT, which may decrease the risk of post-radiation xerostomia while notcompromising target dose coverage in patients with NPC.