Xerostomia and quality of life (QOL) after parotid sparing IMRT for head and neck (HN) cancer: A matched case-control comparison with standard radiotherapy (RT)

Abstract

IMRT for HN cancer has demonstrated salivary output preservation and potential improvement of patient-reported xerostomia (XQ) and HN cancer-related quality of life (HNQOL). However, a comparison of patients receiving IMRT to similar, matched patients receiving standard RT has not been reported and is the subject of this study. This was a prospective longitudinal study of HN cancer patients treated with multisegmental static IMRT at the University of Michigan and patients treated with standard RT at affiliated clinics. At the affiliated clinics, all patients received standard RT, thus avoiding potential selection bias. All patients were given a validated XQ questionnaire and a validated HNQOL questionnaire consisting of four multi-item domains: Eating, Communication, Pain, and Emotion. In both questionnaires, higher scores denote worse symptoms or QOL. The questionnaires were completed before RT and at 1, 3, 6, and 12 months after RT. Patients receiving IMRT were paired with patients receiving standard RT, matched for tumor site, stage, age, gender, and definitive vs. post-operative RT. Differences in the XQ and the HNQOL scores between the two groups were analyzed using matched-control statistical model. Thirty-nine patients (10 receiving standard RT and 29 receiving IMRT) participating in the study completed questionnaires through 12 months. Primary tumor sites for the standard RT patients included 3 base of tongue, 2 supraglottic larynx, and one each of pyriform sinus, retromolar trigone, tonsil, and oral tongue. All were stage III-IV. Each standard RT case was matched with two to four patients (matched for the factors listed in Methods) receiving IMRT. Median prescribed tumor doses were 70.0Gy (range of 63–76.8Gy) for the standard RT arm and 65.3Gy (range of 60-78Gy) for the IMRT arm. The median of mean parotid doses for the standard RT arm were 55Gy (range of 33–64.5Gy) for the ipsilateral and 55Gy (range of 29-72Gy) for the contralateral parotids. The median of mean parotid doses for the parotid-spared arm were 60Gy (range 38.7–67.8Gy) and 21.8Gy (range of 14–55.5Gy) for the ipsilateral and contralateral parotids respectively. The submandibular glands in all patients received ≥ 50Gy. Early post-RT, a significant increase in XQ scores from baseline was seen in both the standard RT and the IMRT groups. An improvement over time was observed in the IMRT group (mean scores of 47, 48, 44, and 37 at 1, 3, 6, and 12 months post-RT, respectively; p = 0.01) but not in the standard RT group (mean scores of 55, 69, 58, and 60 at 1, 3, 6, and 12 months post-RT, respectively; p = 0.3). HNQOL scores also significantly improved over time in the IMRT group (mean scores of 35, 29, 27, and 20 at 1, 3, 6, and 12 months post-RT, respectively; p = 0.001), while no improvement over time was reported by the control group (mean scores of 40, 43, 48, and 50 at 1, 3, 6, and 12 months, respectively; p = 0.827). XQ and HNQOL worsened shortly after the completion of therapy in all patients. Patients treated with standard RT did not report any improvement during the first year after therapy. In contrast, patients matched in important clinical factors who had received IMRT reported significant improvement over time in both XQ and HNQOL. This data quantifies patient-reported benefits of IMRT compared with standard RT in similar, matched patients