Nowadays, surgery, radiation therapy (RT), chemotherapy or combinations of these therapeutic modalities represent the classical options for managing head and neck cancer (HNC). Primary definitive RT is usually performed in case of surgical approaches related to significant functional loss or in patients with medical contraindication to surgery. Due to the anatomic proximity to various structures, the risk of radiation-induced toxicities is important and imposes an adequate assessment, support and surveillance before, during and after treatment. Xerostomia represents the most common RT side effect. With the shift from a three dimensional technique to intensity modulated technology, interpretation of the clinical significance of the xerostomia identified in HNC has become a challenge. In the last decades, various clinical studies searching for predictors of radiation-induced xerostomia have been conducted and the vast majority of these trials focused on factors following parotid-sparing irradiation. One important consequence is that the spared glands in each patient is expected to produce the majority of saliva after RT. Anyway, after RT, parotid glands are damaged, thus their secretion is decreased and their secretory components are altered. Salivary amylase is a glucose-polymer cleavage enzyme mainly produced by parotid glands and it has a major physiologic role in food digestion. Its level can be easily measured in blood sample. A rise in serum salivary amylase seems to be strictly related to the quantity of salivary tissue exposed to ionizing radiation. Our aim is to explore the existence of a direct relationship between the serum salivary amylase rise and development of xerostomia after treatment. It may be useful in assessing the degree of radiation-induced damage.
Head and neck cancer (HNC) is a relatively rare tumor in Italy: it is diagnosed in approximately 19 cases per 100.000 habitants [15]. In general, the use of multimodal approach for HNC has improved cancer-related clinical outcomes but has also increased acute and late toxicities. Xerostomia represents a substantial side effect of radiation therapy (RT) for HNC. Correct analysis of this adverse event is challenging because significant progress in the conventional modalities of surgery, RT and chemotherapy involves not only single treatment but also variations in RT total dose delivery and treatment duration. The quantitative analysis of normal tissue effects in the clinic (QUANTEC) report has highlighted that, in order to minimizing xerostomia, a smallest salivary glands exposure to high radiation dose should be required [2]. The alteration of saliva output after RT can lead to a number of functional disturbances which may be of acute and long-term importance to the patient. Since the introduction of intensity modulated RT (IMRT), a growing number of clinical trials have reported a solid correlation between irradiated parotid volumes and xerostomia after HNC treatment. Although parotid-sparing is now part of routine HNC patient care, interpretation of patient-related factors remains an important challenge. Parotid glands is responsible for a well-documented amylase activity. The relationship between xerostomia and serum salivary amylase level is scarcely reported in the literature [9-12]. In the past two decades, several clinical trials have been performed to determine the role of salivary amylases in predicting xerostomia. These studies reported a transient hyperamylasemia after a dose up to 4 Gy to head and neck region. After that serum amylase declined to normal oiver a further 24-48 hours. A relationship between acute increase and chronic decrease in serum salivary amylase and subsequent xerostomia is logical but has not been established. In an attempt to search for biological predictors, we look at correlations between variations in serum salivary amylase value and severity of radiation-induced xerostomia. A biological marker affecting xerostomia grade would allow for patient therapeutic gain and would maximize his quality of life. Serum salivary amylase variations have an unknown impact on xerostomia, and maybe rigorous serum salivary amylase and xerostomia reporting could be useful to capture these data. An important need exists for a clinical support tool that distills this information into an easily interpretable method that is available to clinicians of all HNC knowledge levels and at all centers. Such a support tool would help clinicians to interpret xerostomia grade and enable them to support optimal treatment decisions for each HNC patient.
References
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