Abstract
PURPOSE: The goal of this study is to report the feasibility and outcomes of hypofractionated proton reirradiation in patients with recurrent thoracic tumors. MATERIALS AND METHODS: Data were retrospectively collected for patients who received hypofractionated proton therapy for recurrent lung cancer at a single facility. Proton reirradiation was delivered using a total of 15 fractions. Patient and tumor characteristics, adverse events, and dose-volume histogram parameters were collected and analyzed descriptively. Tumor control and patient survival were analyzed using Kaplan-Meier statistics. Univariate logistic regression was performed to analyze the relationship between dose-volume histogram parameters and acute and late toxicity. RESULTS: Thirty-one patients who received thoracic proton reirradiation were included. The median patient age was 71.4. Most patients (77.4%) were treated to a total of 60 Gy (RBE) in 15 fractions and had tumors smaller than 50 cc (64.5%). The median interval between the 2 radiation courses was 21.3 months (2.9-227.1). Twenty-one out of 31 plans (67.7%) successfully reached a target PTV coverage with V95% > 95%. Complete prior plan dosimetric information was available for 19 out of 31 plans. The median value of the equivalent dose in 2 Gy (RBE) fractions (EQD2) from the plan sum for the lung V20 Gy (RBE) was 24.9%, and for the V5 Gy (RBE) was 44.8%. The median follow-up was 9.0 months. One-year local, regional, and distant control were 92.3% (95% CI 78.9-100), 71.1% (95% CI 52.1-97.0), and 80.6% (95% CI 64.6-100), respectively. Only two patients experienced grade 3 or higher acute or late toxicities. Acute esophagitis was associated with the esophagus Dmax (P = .031) and Dmean (P = .041). CONCLUSION: This study demonstrates the feasibility and efficacy of a hypofractionated course of proton reirradiation for recurrent thoracic tumors. DATA AVAILABILITY: The data that support the findings of this study are available on request from the corresponding author.