BACKGROUND: Cisplatin-based concurrent chemoradiotherapy is currently considered to be the standard treatment regimen for patients with advanced nasopharyngeal carcinoma, but has well known side-effects such as gastrointestinal reactions, nephrotoxicity, and ototoxicity. Nedaplatin was developed to decrease the toxic effects induced by cisplatin, and in this trial we assessed whether a nedaplatin-based concurrent chemoradiotherapy regimen was non-inferior to a cisplatin-based regimen in patients with locoregional, stage II-IVB nasopharyngeal carcinoma. METHODS: We did an open-label, non-inferiority, phase 3, randomised, controlled trial at two centres in China. Patients aged 18-65 years with non-keratinising stage II-IVB (T1-4N1-3 or T3-4N0) nasopharyngeal carcinoma, a Karnofsky score of at least 70, and adequate haematological, renal, and hepatic function were randomly assigned (1:1) to receive intravenously either nedaplatin 100 mg/m2 or cisplatin 100 mg/m2 on days 1, 22, and 43 for three cycles concurrently with intensity-modulated radiotherapy. Randomisation was done manually using a computer-generated random number code and patients were stratified by treatment centre and clinical stage. Patients and clinicians were not masked to treatment allocation. The primary endpoint was progression-free survival at 2 years; non-inferiority was shown if the upper limit of the 95% CI for the difference in 2-year progression-free survival between the two groups did not exceed 10%. Analyses were by both intention to treat and per protocol, including all patients who received at least one complete cycle of chemotherapy. This trial is registered with ClinicalTrials.gov, number NCT01540136, and is currently in follow-up. FINDINGS: Between Jan 16, 2012, and July 16, 2014, we randomly assigned 402 patients to nedaplatin-based (n=201) or cisplatin-based (n=201) concurrent chemoradiotherapy. In the intention-to-treat population, 2-year progression-free survival was 89·9% (95% CI 85·8-94·0) in the cisplatin group and 88·0% (83·5-94·5) in the nedaplatin group, with a difference of 1·9% (95% CI -4·2 to 8·0; pnon-inferiority=0·0048). In the per-protocol analysis (cisplatin group, n=197; nedaplatin group, n=196), 2-year progression-free survival was 89·7% (95% CI 85·4-94·0) in the cisplatin group and 88·7% (84·2-94·5) in the nedaplatin group, with a difference of 1·0% (95% CI -5·2 to 7·0; pnon-inferiority=0·0020). A significantly higher frequency of grade 3 or 4 vomiting (35 [18%] of 198 in the cisplatin group vs 12 [6%] of 200 in the nedaplatin group, p<0·0001), nausea (18 [9%] vs four [2%], p=0·0021), and anorexia (53 [27%] vs 26 [13%], p=0·00070) was observed in the cisplatin group compared with the nedaplatin group. 11 (6%) patients in the nedaplatin group had grade 3 or 4 thrombocytopenia compared with four (2%) in the cisplatin group (p=0·065). Patients in the cisplatin group had a higher frequency of any grade or grade 3 or 4 late auditory or hearing toxicities than did patients in the nedaplatin group (grade 3 or 4: three [2%] in the nedaplatin group vs 11 [6%] in the cisplatin group, p=0·030). No patients died from treatment-related causes. INTERPRETATION: Our findings show that nedaplatin-based concurrent chemoradiotherapy represents an alternative doublet treatment strategy to cisplatin-based concurrent chemoradiotherapy for patients with locoregional, advanced nasopharyngeal carcinoma. Further investigations are needed to explore the potential use of this treatment as induction or adjuvant chemotherapy or in combination with other agents. FUNDING: National Key R&D Program of China, National Natural Science Foundation of China, Sun Yat-sen University Clinical Research 5010 Program, Sci-Tech Project Foundation of Guangzhou City, National Key Basic Research Program of China, Special Support Plan of Guangdong Province, Sci-Tech Project Foundation of Guangdong Province, Health & Medical Collaborative Innovation Project of Guangzhou City, National Science & Technology Pillar Program during the Twelfth Five-year Plan Period, PhD Start-up Fund of Natural Science Foundation of Guangdong Province, Cultivation Foundation for the Junior Teachers in Sun Yat-sen University, and Fundamental Research Funds for the Central Universities.