Hypofractionated Adjuvant Radiotherapy for Thymic Epithelial Tumors

Overview

This is a multi-center, open-label, single-arm, prospective interventional study evaluating hypofractionated adjuvant radiotherapy (HART) after radical thymothymectomy in patients with thymic epithelial tumors. The study estimates 5-year local control and prospectively characterizes acute and late treatment-related adverse events, quality of life, cardiopulmonary function, and patterns of failure. Photon therapy and proton therapy are both protocol-acceptable modalities and are selected by shared decision-making rather than randomization.

Patients with pathologically confirmed thymic epithelial tumors, including thymoma and thymic carcinoma, who have undergone radical thymothymectomy and have an indication for postoperative radiotherapy will receive hypofractionated adjuvant radiotherapy. Base regimens are 40 Gy (RBE) in 15 fractions or 42.5 Gy (RBE) in 16 fractions. For patients with incomplete resection, close margins, residual disease, or other high-risk tumor-bed features, an optional tumor-bed boost may be delivered at investigator discretion, using 10 Gy (RBE) in 4 fractions or, for R2 macroscopic residual disease, 16 Gy (RBE) in 6 fractions. Treatment is delivered once per workday over approximately 3 to 4 weeks, with an additional 1 to 2 weeks if boost is delivered. Photon therapy with IMRT or VMAT/RapidArc and proton therapy with pencil-beam scanning IMPT are both allowed. Mixed photon and proton treatment courses are not allowed. Target volumes include the mediastinal tumor bed, with pleural or pericardial tumor bed coverage when clinically indicated. Routine elective irradiation of uninvolved mediastinal lymph node stations is not allowed. Participants are followed at baseline, during treatment, and after treatment at 1, 3, and 6 months, every 6 months through 2 years, and then annually until progression, death, or completion of protocol-specified follow-up. Assessments include clinical evaluation, adverse event assessment using CTCAE version 6.0, CT imaging assessed using RECIST 1.1, pulmonary function testing, cardiac sonography and electrocardiography, EORTC QLQ-C30, and protocol-specified dosimetric analyses. The primary efficacy analysis uses a Bayesian beta-binomial model for the 5-year local control rate. The study requires 55 evaluable patients, with a total accrual goal of 69 patients to account for approximately 20 percent attrition. Safety monitoring includes semiannual interim reports, annual reports to the ethics committee, and stopping rules for excessive serious adverse events related to the intervention.