Radiation therapy

Salivary gland irradiation incidental to treatment of head and neck malignancies or Hodgkin lymphoma causes a qualitative and quantitative change in salivary flow, which can be reversible after doses of lower than 40 Gy but may be irreversible after higher doses, depending on whether sensitizing chemotherapy is also administered.[18]

In a German study of 114 pediatric patients, the risk of acute and late xerostomia increased with parotid and submandibular gland dose. In general, grade 1 or higher xerostomia was seen in patients who received a maximum dose of higher than 20 Gy to the salivary glands. The odds of both acute and late xerostomia were higher in patients who received concurrent chemotherapy compared with those who received radiation therapy alone, with an OR for acute xerostomia of 3.64 (95% CI, 1.49–8.89) and for late xerostomia of 5.15 (95% CI, 1.20–22.15).[21]

The Pediatric Normal Tissue Effects in the Clinic (PENTEC) initiative reported on late effects for childhood cancer survivors who were treated with radiation therapy for head and neck cancers.[22] Grades 1 or higher xerostomia were seen in patients who received a maximum dose of more than 20 Gy to the salivary glands. The odds of both acute and chronic xerostomia were greater in patients who had received concurrent chemotherapy and radiation therapy (acute xerostomia OR, 3.64; 95% CI, 1.49–8.89 and late xerostomia OR, 5.15; 95% CI, 1.20–22.15), compared with patients who were treated with radiation therapy alone. A mean parotid dose of 35 to 40 Gy was associated with a 32% risk of higher than grade 2 acute xerostomia and a 13% to 32% risk of chronic xerostomia.