Parotid-Sparing Versus Conventional Whole Brain Radiation Therapy: A Multi-Institutional Randomized Clinical Trial
Kyle Wang1, Allison M Deal2, Colette J Shen3
1Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, Ohio.
Purpose:
Xerostomia (dry mouth) is common after conventional whole brain radiation therapy (WBRT) for brain metastases and is associated with parotid dose. No studies have reported whether parotid-sparing WBRT reduces this toxicity. We assessed whether parotid-sparing WBRT reduces xerostomia compared with conventional WBRT.
Methods And Materials:
Patients receiving WBRT (30-35 Gy in 10-15 fractions) using 3-dimensional fields were enrolled at 3 academic centers from 2018 to 2021. Patients were randomized to conventional fields (covering C1-C2 vertebrae inferiorly without prospective delineation of parotids) versus parotid-sparing fields (omission of C-spine coverage; parotids delineated and V20Gy limited to 25%). Patients completed the University of Michigan Xerostomia Questionnaire (scored 0-100, higher = worse xerostomia) at baseline, within 5 days of WBRT completion (EndRT), 2 weeks, 1, 3, and 6 months. The primary endpoint was xerostomia score at 1 month (1M), analyzed as proportion with ≥15-point increase and as model-estimated mean xerostomia score. The secondary endpoint was marginal tumor relapse (≤1 cm outside WBRT fields).
Results:
A total of 56 patients were randomized and 48 (24 in each arm) were eligible for analysis. Mean parotid dose was 17 versus 10 Gy with conventional versus parotid-sparing WBRT. At 1M, mean xerostomia score was 17 versus 8 (P = .06). The primary endpoint at 1M was not met; the proportion with ≥15-point increase in xerostomia score did not differ significantly between conventional versus parotid-sparing fields (12% vs 16%; P = .56). However, proportion with ≥15-point increase in xerostomia score at EndRT was higher with conventional versus parotid-sparing treatment (52% vs 22%; P = .05). Parotid V5Gy (P = .04) and V10Gy (P = .05) were associated with xerostomia at EndRT. On multivariable analysis, parotid-sparing WBRT was associated with improved xerostomia at EndRT (P = .04) but not at 1M (P = .06). There were no marginal relapses in either arm.
Conclusions:
Parotid sparing without coverage of upper cervical vertebra appears safe and potentially reduces acute xerostomia in patients with limited life expectancy receiving conventional WBRT.
