6 vs 3 Cycles of Neoadjuvant Chemotherapy for Potentially Resectable Locally Advanced Thymic Epithelial Tumors

Inclusion Criteria: * Histologically or cytologically confirmed thymic epithelial tumor (thymoma or thymic carcinoma) * Locally advanced, potentially resectable disease (Masaoka-Koga stage III or IVA), as evaluated by a multidisciplinary team (MDT) including thoracic surgery and thoracic oncology * Age 18 to 65 years * Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1 * Adequate bone marrow function: absolute neutrophil count (ANC) ≥1.5×10⁹/L, platelet count ≥100×10⁹/L, hemoglobin ≥90 g/L * Adequate liver function: total bilirubin ≤1.5× upper limit of normal (ULN); alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤2.5×ULN * Adequate renal function: creatinine clearance ≥50 mL/min (Cockcroft-Gault formula) * No prior systemic anticancer therapy for thymic epithelial tumor * At least one measurable lesion per RECIST v1.1 * Willing to accept randomization and able to comply with study procedures * Written informed consent obtained prior to any study-related procedures Exclusion Criteria: * Prior chemotherapy, targeted therapy, or immunotherapy for thymic epithelial tumor * Prior thoracic radiation therapy * Active autoimmune disease requiring systemic treatment within the past 2 years * Known hypersensitivity or contraindication to study drugs (cisplatin, epirubicin, etoposide, ifosfamide, or any component of these formulations) * Severe cardiac dysfunction: New York Heart Association (NYHA) class III or IV heart failure, or left ventricular ejection fraction (LVEF) \<50% * Active hepatitis B (HBsAg positive with HBV DNA ≥2000 IU/mL), active hepatitis C, or known HIV infection * Pregnancy or lactation; women of childbearing potential unwilling to use adequate contraception * Other malignancy within 5 years prior to enrollment, except for adequately treated basal cell carcinoma, squamous cell carcinoma of the skin, or carcinoma in situ of the cervix * Uncontrolled active infection requiring systemic therapy * Any condition that, in the investigator's judgment, would preclude safe participation in the study