Selective partial salivary glands sparing during intensity-modulated radiation therapy for nasopharyngeal carcinoma ⁎

Abstract

Abstract Objective This study evaluated the dosimetric consequences of selective partial salivary gland sparing during 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 each patient: conventional (control) and partial salivary glands-sparing (treatment), with dose constraints to the entire parotid glands or partial salivary glands (including the parotid and submandibular glands, delineated with the adjacent distance of at least 0.5 cm between the glands and PTV, the planning target volume) in planning, 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 (the minimum dose) of PTV, homogeneity index (HI), conformity index (CI), and the mean dose and percentage of the volume receiving 30 Gy or more (V30) for the parotid glands and submandibular glands. Results Treatment plans had significantly lower mean doses and V30 to both the entire parotid glands and partial parotid glands than those in control plans. The mean doses to the partial submandibular glands were also significantly lower in treatment plans than in control plans. The PTV coverage was comparable between the two plans, as indicated by V100%, V95%, Dmin, CI, and HI. The doses to critical structures, including brainstem 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 and submandibular glands during IMRT, which may decrease the risk of post-radiation xerostomia while not compromising target dose coverage in patients with NPC.