Dosimetric factors associated with long-term patient-reported outcomes after definitive radiotherapy of patients with head and neck cancer.

Background: The aim of this study was to explore the relationships between dosimetric parameters of organs at risk and patient-reported outcomes (PRO) after radiotherapy of patients with head and neck cancer.

Methods: PRO data of 53 patients with head and neck cancer treated with radiotherapy were prospectively collected. These data concerned health-related quality of life (HRQOL) and were collected using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (QLQ-C30) and head and neck cancer module (QLQ-H&N35). Patients were divided into "severe-deterioration" and "mild-deterioration" groups on the basis of degree of deterioration HRQOL > 6 months after completing treatment. The relationships between HRQOL deteriorations and patient-related or dosimetry-related factors were evaluated. P < 0.0013 according to Bonferroni correction was considered to denote statistical significance.

Results: Regarding "trouble with social eating (HNSO)" and "coughing (HNCO)," there were significant differences between the severe-deterioration and mild-deterioration groups in mean dosages to the superior pharyngeal constrictor muscle (SPC) (HNSO: 62.5 Gy vs 54.2 Gy; p = 0.00029, and HNCO: 61.5 Gy vs 54.1 Gy; p = 0.0012) and parotid gland (HNSO: 24.1 Gy vs 20.5 Gy; p = 0.000056, and HNCO: 24.2 Gy vs 20.3 Gy; p = 0.00043). Regarding "nausea and vomiting," there was a significant difference between the two groups in the mean dosage to the middle pharyngeal constrictor muscle (MPC: 61.9 Gy vs. 58.4Gy; P = 0.00059).

Conclusions: We found that dosages to the SPC and parotid gland were associated with severe deterioration in HRQOL attributable to difficulty in HNSO and HNCO, whereas dosage to the MPC was associated with severe deterioration attributable to nausea and vomiting.