Feasibility and efficacy of hypofractionated proton reirradiation for recurrent lung cancer

The goal of this study is to report the feasibility and outcomes of hypofractionated proton reirradiation in patients with recurrent thoracic tumors.

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.

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).

This study demonstrates the feasibility and efficacy of a hypofractionated course of proton reirradiation for recurrent thoracic tumors.

The data that support the findings of this study are available on request from the corresponding author.