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Original Investigation
November 29, 2018

Assessment of Risk of Xerostomia After Whole-Brain Radiation Therapy and Association With Parotid Dose

Author Affiliations
  • 1Department of Radiation Oncology, University of North Carolina Hospitals, Chapel Hill
  • 2Lineberger Comprehensive Cancer Center Biostatistics Core, University of North Carolina Hospitals, Chapel Hill
  • 3Northeastern Radiation Oncology, Glens Falls, New York
JAMA Oncol. Published online November 29, 2018. doi:10.1001/jamaoncol.2018.4951
Key Points

Question  Is xerostomia a toxic effect of whole-brain radiation therapy?

Findings  In this cohort study of 73 patients who received whole-brain radiation therapy, clinically significant xerostomia was common, was bothersome to patients, occurred as early as the end of treatment, and often persisted for months. Furthermore, xerostomia was statistically significantly associated with radiation dose to the parotid glands.

Meaning  This study appears to justify minimization of parotidradiation doses and associated adverse effects in patients who receive this therapy and who often do not survive long enough for salivary recovery.

Abstract

Importance  Whole-brain radiation therapy (WBRT) delivers a substantial radiation dose to the parotid glands, but the parotid glands are not delineated for avoidance and xerostomia has never been reported as an adverse effect. Minimizing the toxic effects in patients receiving palliative treatments, such as WBRT, is crucial.

Objective  To assess whether xerostomia is a toxic effect of WBRT.

Design, Setting, and Participants  This observational cohort study enrolled patients from November 2, 2015, to March 20, 2018, at 1 academic center (University of North Carolina Hospitals) and 2 affiliated community hospitals (High Point Regional Hospital and University of North Carolina Rex Hospital). Adult patients (n = 100) receiving WBRT for the treatment or prophylaxis of brain metastases were enrolled. Patients who had substantial baseline xerostomia or did not complete WBRT or at least 1 postbaseline questionnaire were prospectively excluded from analysis and follow-up. Patients received 3-dimensional WBRT using opposed lateral fields covering the skull and the C1 or C2 vertebra. Per standard practice, the parotid glands were not prospectively delineated.

Main Outcomes and Measures  Patients completed the University of Michigan Xerostomia Questionnaire and a 4-point bother score at baseline, immediately after WBRT, at 1 month, at 3 months, and at 6 months. The primary end point was the 1-month xerostomia score, with a hypothesized worsening score of 10 points from baseline.

Results  Of the 100 patients enrolled, 73 (73%) were eligible for analysis and 55 (55%) were evaluable at 1 month. The 73 patients included 43 women (59%) and 30 men (41%) with a median (range) age of 61 (23-88) years. The median volume of parotid receiving at least 20 Gy (V20Gy) was 47%. The mean xerostomia score was 7 points at baseline and was statistically significantly higher at each assessment period, including 21 points immediately after WBRT (95% CI, 16-26; P < .001), 23 points (95% CI, 16-30; P < .001) at 1 month, 21 points (95% CI, 13-28; P < .001) at 3 months, and 14 points (95% CI, 7-21; P = .03) at 6 months. At 1 month, the xerostomia score increased by 20 points or more in 19 patients (35%). The xerostomia score at 1 month was associated with parotid dose as a continuous variable and was 35 points in patients with parotid V20Gy of 47% or greater, compared with only 9 points in patients with parotid V20Gy less than 47% (P < .001). The proportion of patients who self-reported to be bothered quite a bit or bothered very much by xerostomia at 1 month was 50% in those with parotid V20Gy of 47% or greater, compared with only 4% in those with parotid V20Gy less than 47% (P < .001). At 3 months, this difference was 50% vs 0% (P = .001). Xerostomia was not associated with medication use.

Conclusions and Relevance  Clinically significant xerostomia occurred by the end of WBRT, appeared to be persistent, and appeared to be associated with parotid dose. The findings from this study suggest that the parotid glands should be delineated for avoidance to minimize these toxic effects in patients who undergo WBRT and often do not survive long enough for salivary recovery.

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