Xerostomia in Head and Neck Cancer Patients Treated with Volumetric Modulated Arc Therapy: 1 year Prospective Cohort Study

Abstract

Background: Volumetric modulated arc therapy (VMAT) is a radiotherapy technique to treat cancer patients. Side effects are due to proximity of organs from the target volume. Xerostomia is a common complication in head and neck cancer radiotherapy and decreases the parotid gland ability to produce saliva. Objective: This study aimed to determine the occurrence of xerostomia caused by radiation and relation between of radiation received by parotid glands and salivary flow rate in head and neck cancer patients treated with VMAT. Method: This study prospective for head and neck cancer 84 case treated with VMAT at Chonburi Cancer Hospital from 2022 to 2024, with radiation dose 60 to 70 Gray. Measure unstimulated salivary flow rate before radiation, during the 4^th week, end of radiotherapy, 3 months and 1 year after treatment. The diagnostic criterion for xerostomia is an unstimulated salivary flow rate less than 0.1 ml/min, in accordance with previous literature. Result: 84 patients complete study, 50 and 65 case developed xerostomia during the 4^th week and end of radiotherapy, respectively. After 3 months, the patients were 69 case developed xerostomia 58 case. After 1 year, the patients were 56 case developed xerostomia 37 case. The average salivary flow rate before radiation therapy, during the 4^th week, end of radiotherapy, 3 months and 1 year were 0.22±0.16, 0.09±0.08, 0.06±0.06, 0.04±0.05, and 0.07±0.04 ml/min, respectively. When patients were grouped according mean dose of parotid gland, average salivary flow rate in groups mean dose to both parotid glands or at least one not exceed 26 Gray were not significant difference at 1 year. Conclusion: Parotid gland sparing VMAT for head and neck cancer patients, the mean dose to both parotid glands or at least one should not exceed 26 Gray in order to reduce the occurrence of xerostomia.