6006Background: In intensity-modulated radiotherapy (IMRT) era, concurrent chemoradiotherapy (CCRT) with either every three week (ETW) or once a week (OAW) cisplatin is accepted practice for locoregionally advanced nasopharyngeal carcinoma (LANPC). However, ETW and OAW were never prospectively compared in phase 3 clinical trials. This study is to assess the efficacy and toxicity profiles of CCRT with ETW versus OAW schedule of cisplatin. Methods: We conducted an open-label phase 3 multicentre randomised controlled trial in an endemic area. Patients with stage II-IVB NPC were randomly assigned to receive either cisplatin 100 mg/m² every 3 weeks for 2 cycles or cisplatin 40 mg/m² weekly up to 6 cycles concurrently with IMRT. IMRT in both groups was given as 2.19-2.34 Gy per fraction with five daily fractions per week for 6-7 weeks to a total dose of 68-70 Gy to the primary tumor and 62-68 Gy to the involved neck area. The primary endpoint was failure-free survival. Intention-to-treat population was adopted ...