Original Research Reduced-dose radiotherapy for Epstein-Barr virus DNA selected staged III nasopharyngeal carcinoma: A single-arm, phase 2 trial

Background: Radiotherapy-related toxicities of nasopharyngeal carcinoma (NPC) caused by a standard dose of 70 Gy remain a critical issue. Therefore, we assessed whether a radiotherapy dose of 60 Gy was non-inferior to the standard dose in patients with low-risk stage III NPC with a favourable response to induction chemotherapy (IC). Patients and methods: We did a single-arm, single-centre, phase II clinical trial in China. Patients with low-risk (Epstein-Barr virus [EBV] DNA level < 4000 copies/ml) stage III NPC were treated with two cycles IC. Patients with complete/partial response and undetectable EBV DNA level were assigned 60 Gy intensity-modulated radiotherapy concurrently with three cycles of cisplatin. The primary end-point was 2-year progression-free survival (PFS). This trial is registered with ClinicalTrials.gov, number NCT 03668730. Results: One patient quit because of withdrawal of informed consent after IC. In total, 215 patients completed two cycles of IC, after which 116 (54.0%) and 99 (46.0%) patients were assigned 60 and 70 Gy radiotherapy, respectively. For 215 patients, the 2-year PFS was 90.7% (95% CI, 86.8%-94.6%) with a median follow-up of 43.9 months (interquartile range [IQR], 39.8-46.2). For patients treated with 60 Gy radiotherapy, the 2-year PFS rate was 94.8% (95%CI 90.7%-98.9%) with a median follow-up of 43.9 months (IQR 40.2-46.2). The most common late toxicity was grade 1-2 dry mouth (incidence rate: 54.3%). No grade 3+ long-term adverse event was observed, and most quality-of-life items, domains, and symptom scores returned to baseline by 6 months. Conclusion: Reduced-dose radiation (60 Gy) is associated with favourable survival outcomes and limited treatment-related toxicities in patients with low-risk stage III NPC sensitive to IC. (c) 2023 Elsevier Ltd. All rights reserved.