ESTRO 2024 - Abstract Book

S118 ESTRO 2024 Concomitant chemotherapy was oral Navelbine®50 mg three times a week and cisplatin or carboplatin administered at weeks one and four. In 2019, adjuvant Durvalumab® became standard for selected patients according to national guidelines. Toxicity was registered prospectively at the start, weekly during radiotherapy, every 3 months for 2 years, hereafter every 6 months for another 3 years, and yearly from 5-10 years after randomization using CTCAE v4.0. In addition, the patient had a CT scan before each follow-up visit. The primary endpoint was time to loco-regional failure from randomization. Secondary endpoints included overall survival, progression-free survival, acute and late toxicity. The sample size calculations requested 350 patients to be enrolled in the study, in order to detect a hazard ratio (HR) of 0.57 for loco-regional control with 80% power and two-sided a=0.05 (based on pre-study dose response modelling). Recruitment of the pre-planned number of patients was finalized in March 2023. Strict quality assurance (QA) with focus on definition of target, PET volume, and OAR and treatment planning with homogeneous and heterogeneous escalated dose distribution was done pre-trial, and all centers had to demonstrate QA compliance before local trial initiation. Preplanned interim analyses to evaluate acute and semi-acute toxicity were planned after the first 20, 40, and 60 patients in the dose escalated group. In addition, an interim survival analysis was planned when half the total number of patients had been randomized. The trial was approved by Committees on Health Research Ethics and registered with ClinicalTrials.gov (NCT02354274). From January 2015 to March 2023, 351 patients were randomized across 7 radiotherapy centres in Denmark and Norway; 178 in the standard and 173 in the experimental arm. Baseline characteristics and treatment compliance are summarized in Table 1. The majority of the patients had non-squamous carcinoma, stage IIIA-IIIB, and were current or previous smokers. Ninety-seven percent of the patients received radiotherapy as scheduled, with no differences between the two groups. Invited Speaker Results

The treatment was determined safe in the pre-planned interim analyses on early toxicity and overall survival.