Parotid Sparing Study in Head and Neck Cancer Patients Receiving Bilateral Radiation Therapy: One-year Results

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Abstract
Many patients with head and neck cancers receive radiation therapy as part of their treatment which frequently causes considerable morbidity, including various degrees of permanent salivary gland dysfunction. Three-dimensional treatment planning [3-DTP] and conformational dose delivery constitute a new therapeutic modality that conforms the high-dose radiation volume to the shape of the tumor volume while minimizing the dose to tissue that is not at risk of containing cancer. The treatment volumes for head and neck tumors as well as parotid glands can be well-defined on cross-sectional CT imaging techniques. The purpose of this investigation is to determine if 3-DTP and conformational dose-delivery could minimize radiation dose and salivary gland dysfunction to contralateral parotid glands in patients with head and neck cancers. Eleven patients with head and neck cancers who required bilateral radiation therapy were treated with 3-DTP. Unstimulated and stimulated bilateral parotid saliva was collected prior to radiotherapy, weekly during treatment, and 1, 3, 6, and 12 months after the completion of radiotherapy. Treated parotid glands received an average dose of 5745 cGy, while spared glands received only 1986 cGy (p < 0.0001). Unstimulated and stimulated parotid flow rates decreased dramatically in treated glands after the initiation of radiotherapy, remained at extremely low rates without any improvements, and were significantly lower at 1 year after radiotherapy compared with baseline. Conversely, parotid flow rates in spared glands underwent mild changes during radiotherapy and were approximately 50% of baseline values. The results of this study suggest that with the use of 3-DTP, contralateral parotid gland function can be partially preserved for at least 1 year in patients with head and neck cancers requiring bilateral radiation.