Prospective study of proton beam radiation therapy for adjuvant and definitive treatment of thymoma and thymic carcinoma: Early response and toxicity assessment

Background and purpose: Radiation is an important modality in treatment of thymic tumors. However, toxicity may reduce its overall benefit. We hypothesized that double-scattering proton beam therapy (DS-PT) can achieve excellent local control with limited toxicity in patients with thymic malignancies. Methods and materials: Patients with thymoma or thymic carcinoma treated with DS-PT between 2011 and 2015 were prospectively analyzed for toxicity and patterns of failure on an IRB-approved study. Results: Twenty-seven consecutive patients were evaluated. Patients were a median of 56 years and had thymoma (85%). They were treated with definitive (22%), salvage (15%) or adjuvant (63%) DS-PT to a median of 61.2/1.8 Gy [CGE]. No patient experienced grade >= 3 toxicity. Acute grade 2 toxicities included dermatitis (37%), fatigue (11%), esophagitis (7%), and pneumonitis (4%). Late grade 2 toxicity was limited to a single patient with chronic dyspnea. At a median follow-up of 2 years, 100% local control was achieved. Three-year regional control, distant control, and overall survival rates were 96% (95% CI 76-99%), 74% (95% CI 41-90%), and 94% (95% CI 63-99%), respectively. Conclusions: This is the first cohort and prospective series of proton therapy to treat thymic tumors, demonstrating low rates of early toxicity and excellent initial outcomes. (C) 2016 Elsevier Ireland Ltd. All rights reserved.