Dose-escalated stereotactic body radiotherapy re-irradiation in patients with recurrent head and neck cancer: a prospective phase 2 study using automated non-coplanar volumetric modulated arc therapy.

Abstract

Re-irradiation for recurrent head and neck cancer is associated with poor local control and significant treatment-related toxicity. We hypothesized that automated non-coplanar volumetric modulated arc therapy (VMAT) can deliver more conformal, dose-escalated stereotactic body radiotherapy (SBRT) plans than conventional VMAT, which may improve local control without increasing toxicity. This was a single-arm, phase II trial that enrolled patients with histologically-confirmed, recurrent head and neck cancer (diameter < 5 cm) with prior head and neck radiotherapy. Patients were planned for treatment using both conventional VMAT (≤40 Gy) and automated non-coplanar VMAT (≤55 Gy) in 5 every-other-day fractions. Non-coplanar VMAT plans were selected if they could deliver higher planning target volume doses without higher organ-at-risk doses. The primary endpoints were one-year local control (compared to the historical rate of 60 % with SBRT using conventional VMAT) and one-year grade ≥ 3 treatment-related toxicity (compared to the historical rate of 20 %). Local control was estimated via Kaplan-Meier method. Toxicities were graded using Common Terminology Criteria for Adverse Events, v5.0. Twenty-nine patients were enrolled between February 2020-November 2023. Median follow-up was 18.1 months (interquartile range, 10.9-36.3). Non-coplanar VMAT plans were selected over conventional VMAT for all patients. One-year local control was 83.8 % (95 % confidence interval [CI], 62.4-93.6 %). One-year grade ≥ 3 toxicity was 17.4 %. Automated non-coplanar VMAT achieved superior one-year local control compared to the historical local control rate without higher grade ≥ 3 toxicity. This represents one of the highest local control rates reported in a prospective trial of head and neck re-irradiation and a new approach to head and neck SBRT.