Parotid-sparing radiotherapy: does it really reduce xerostomia?

Parotid-sparing radiotherapy (PSRT) was introduced for patients with selected head and neck cancer requiring bilateral upper-neck irradiation at our centre in 2000. The aim of this study was to compare the subjective degree of xerostomia in patients treated with PSRT between January 2000 and June 2003 with patients treated using conventional techniques (radiotherapy) over the same period.

Eligible patients were required to have completed treatment 6 months previously and be recurrence-free at the time of interview. PSRT was defined as conformal radiotherapy, in which the mean dose to at least one parotid gland was 33 Gy or less, as determined by the dose-volume histogram. Patients receiving radiotherapy were treated with standard parallel-opposed fields, such that both parotids received a minimum of 40 Gy. Xerostomia was assessed using a validated questionnaire containing six questions with a rating between 0 and 10. Lower scores indicated less difficulty with xerostomia.

Thirty-eight eligible patients treated with PSRT were identified: 25 with oropharyngeal cancer and 13 with nasopharyngeal cancer (NPC). The mean overall questionnaire score (Q1-5) for this group was 4.20 (standard error = 0.33). Forty-four patients (24 oropharyngeal, 21 NPC) treated with radiotherapy over the same period were eligible. The mean overall questionnaire score (Q1-5) for this group was 5.86 (standard error = 0.35). The difference in mean overall scores between the two groups of patients was statistically significant (P < 0.001), as were the scores for four of the six individual questions.

These results suggest that PSRT offers improved long-term xerostomia-related quality of life compared with conventional radiotherapy.