GELAD-Based Response-Adapted Treatment for Early-Stage Extranodal NK/T-Cell Lymphoma

This is an investigator-initiated, prospective, multicenter, response-adapted master protocol for previously untreated patients with stage IE or IIE extranodal NK/T-cell lymphoma of the upper aerodigestive tract. All enrolled participants first receive two 21-day cycles of GELAD induction chemotherapy consisting of gemcitabine, etoposide, pegaspargase, and dexamethasone. Early response assessment is performed 14 to 21 days after completion of the second GELAD cycle and includes whole-body PET/CT, quantitative plasma EBV DNA, contrast-enhanced MRI or CT of the primary site, and nasal endoscopy. Participants are subsequently assigned to one of three response-defined modules. PART A includes participants who achieve complete metabolic response on PET/CT and have negative plasma EBV DNA. These participants are randomized centrally in a 1:1 ratio, stratified by NRI 0-1 versus NRI 2 or higher, to receive either 50 Gy in 25 fractions (A0, standard-dose radiotherapy) or 40 Gy in 20 fractions (A1, reduced-dose radiotherapy). Both groups subsequently receive two additional cycles of GELAD. PART A is designed as a noninferiority comparison. The primary endpoint is the 24-month progression-free survival rate from randomization. The prespecified noninferiority margin for the absolute difference in PFS24 between A1 and A0 is -10 percentage points. A total of 280 participants are planned for randomization in PART A. PART B includes participants with partial response on PET/CT and negative plasma EBV DNA. These participants are not randomized and receive 50 Gy in 25 fractions followed by two additional cycles of GELAD. PART B serves as a prospective standard-treatment platform cohort and has no formal primary hypothesis test. PART C includes participants with stable disease, local or regional progressive disease that remains within a field amenable to curative radiotherapy, or partial response with persistent positive plasma EBV DNA after two cycles of GELAD. Participants with distant progression or progression to stage III or IV disease are considered to have induction failure and do not enter PART C. Participants in PART C receive 50 Gy in 25 fractions followed by sintilimab 200 mg intravenously every 3 weeks. Sintilimab is administered for at least 24 weeks. Treatment is discontinued when PET/CT complete metabolic response and plasma EBV DNA negativity have both been sustained for at least 24 weeks according to protocol-defined confirmation criteria. The maximum duration of sintilimab is 24 months or 35 cycles. PART C is a single-arm phase 2 module. Its primary endpoint is the 24-month progression-free survival rate from PART C module registration, evaluated against a prespecified null benchmark of 55%. Approximately 620 participants are expected to be registered in the master protocol. Enrollment may be increased, based only on a blinded feasibility review of actual module-assignment proportions, to a maximum of 660 participants. Participants are followed every 3 months during the first 2 years after completion or discontinuation of protocol treatment, every 6 months during years 3 through 5, and annually thereafter.