The Clinical Study of Post-operative Proton Radiotherapy for Thymus Tumor

Inclusion Criteria: * Patients with stage II-III (Masaoka-Koga) thymus epithelial malignancies without a history of thoracic radiation therapy, who have undergone radical surgery and have a definite pathological diagnosis, and undergone surgery for R0 (no microscopic residual disease) or R1 (microscopic residual disease) resection, and have indication of postoperative radiation therapy. * Sign informed consent. * Between the ages of 18 and 70. * ECOG general status score of 0-2. * The expected survival is at least 6 months. * Adequate organ function: 1). Blood function: absolute neutrophil count (ANC) ≥1.5 x 109/L, platelet count ≥80 x 109/L, hemoglobin ≥9 g/dL 2). Lung function: FEV1\>25%, DLCO\>25% 3). Cardiac function: no serious pulmonary hypertension, cardiovascular and cerebrovascular diseases, peripheral vascular diseases, serious chronic heart disease and other complications that may affect radiotherapy.4). Adequate liver function: total bilirubin \<1.5 times the upper limit of normal value, and AST, ALT\<2 times the upper limit of normal value. 5). Adequate renal function: serum creatinine ≤1.5 times the upper limit of normal or calculated creatinine clearance ≥50 ml /min, and urinary protein \<2+. Patients with a baseline urinary protein level of 2+ or more should have a 24-hour urine collection and evidence of a 24-hour urinary protein level of 1g or less. Exclusion Criteria: * Complicated with other malignant tumors that have not been controlled. * Have large quantity of pleural or pericardial effusion. * Patient whose particle radiotherapy plan cannot meet the minimum target dose coverage and dose volume limitation requirements, or cannot meet the dose constrains of normal tissue or organs. * Chest radiation therapy or radioactive particle implantation history. * Cardiac pacemakers or other internal metal prosthesis implants that may be affected by high-energy radiation or may affect the dose distribution to the radiation target area. * HIV positive. Hepatitis virus replication phase, need to receive antiviral therapy, but because of concomitant disease cannot receive antiviral therapy. Active stage of syphilis. * A history of mental illness may hinder the completion of treatment. * With serious comorbidity that may interfere with radiotherapy, including: (a) Acute infectious diseases or acute active phase of chronic infection. b) Unstable angina pectoris, congestive heart failure, myocardial infarction that has been hospitalized in the past 6 months. c) Exacerbations of chronic obstructive pulmonary disease or other respiratory conditions requiring hospitalization. d) Severely impaired immune function. e) Diseases with excessive sensitivity to radiation such as ataxia telangiectasia. f) Other diseases that may affect particle radiotherapy. * Other circumstances that the physician considers inappropriate to participate in clinical study.