Uniform expansion vs. non-uniform expansion of gross tumor volume based on recurrence patterns to form planning target volume of stereotactic body radiation therapy for locally advanced pancreatic cancer: protocol of a randomized phase II study

Abstract • Background: There is no guideline or consensus on target delineations of stereotactic body radiation therapy (SBRT) for locally advanced pancreatic cancer (LAPC). Two different modes of target delineation are compared to identify a superior one beneficial for improvement of outcomes.• Methods: The study is a single-center, randomized phase II trial. Patients are randomly allocated to two groups with different delineations of planning target volume (PTV) of SBRT followed by a same chemotherapy regimen. Patients in Arm A receive uniform expansions of gross tumor volume (GTV) to form PTV, while PTV is contoured by non-uniform expansions of GTV based on recurrence patterns in Arm B. The primary endpoint is 1-year local control rate (1y-LC), and the secondary endpoints are disease progression-free survival (PFS), overall survival (OS), and treatment-related toxicity. Radiotherapy-induced adverse events (AEs) are recorded according to Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer (RTOG/EORTC), and chemotherapy AEs are graded according to Common Terminology Criteria for Adverse Events version 5.0 (CTCAE 5.0). This trial protocol has been approved by the Ethics committee of Changhai hospital. The ethics number is CHEC2020-099.• Discussion: Empirical uniform expansions of GTV is commonly practiced in most centers for delineations of PTV. However, limited evidence has confirmed potential benefits of this method. Therefore, we designed this prospective phase II study to investigate the hypothesis that better outcomes are found in the proposed method in our previous study than that used now.• Trial registration: Registration number: NCT04699539. Date of registration: 07 January, 2021.