The QUANTEC criteria for parotid gland dose and their efficacy to prevent moderate to severe patient-rated xerostomia

Background. Recently, the Quantitative Analysis of Normal Tissue Effect in the Clinic (QUANTEC) Group defined dose-volume constraints for the parotid glands to avoid severe xerostomia. The aim of this study was to determine if application of these QUANTEC criteria also protected against moderate-to-severe patient-rated xerostomia. Material and methods. The study population consisted of 307 head and neck cancer patients treated with primary (chemo) radiotherapy, either with 3D-CRT (56%) or with IMRT (44%). All patients participated in a standard follow-up program in which radiation-induced toxicity and quality of life were prospectively assessed. Patients who met the QUANTEC criteria were classified as low risk and otherwise as high risk. Results. In total, 41% of the patients (treated with 3D-CRT and IMRT) were classified as low risk patients. In the group treated with 3D-CRT and IMRT, it was possible to meet the QUANTEC criteria in 47% and 32% of the patients, respectively. Sparing the parotid glands with IMRT was considerably more difficult in patients with lymph node metastases and in patients with nasopharyngeal and oropharyngeal tumours. Low risk patients reported significantly less moderate-to-severe xerostomia than high risk patients. However, the predicted risk of elderly patients and patients with pre-existing minor patient-rated xerostomia at baseline was > 20%, even when the QUANTEC criteria were met. Conclusions. Significantly lower rates of radiation-induced patient-rated xerostomia were found among low risk patients treated according to the QUANTEC criteria, but these criteria do not completely protect against xerostomia. Particularly in elderly patients and patients already suffering from minor xerostomia at baseline, the QUANTEC criteria do not sufficiently protect against persistent, moderate-to-severe patient-rated xerostomia.