Post‐induction lymph node delineation in nasopharyngeal cancer: A single‐center experience

Abstract Background We routinely delineate the gross tumor volume (GTV) for the lymph nodes (LN) based on post‐induction chemotherapy (IC) MRI in nasopharyngeal carcinoma (NPC). Herein, we investigated the sufficiency of this method, particularly in high‐risk LNs. Methods Eighty‐one LNs with a high‐risk of clinical extranodal extension and/or ≥3‐cm diameter in 58 patients were evaluated. A new GTV covering the pre‐IC LN volume was delineated for each LN. Results The median volume reduction was 72.5% for the GTV and 53.1% for the planning target volume. After a median 43 months, the overall LN local control rate was 97.5%. The 2‐ and 5‐year LN recurrence‐free survival, overall survival, and disease‐free survival rate was 88.3% and 84.4%, 92.5% and 85.1%, and 86.8% and 79.2%, respectively. Conclusion IC yields a significant reduction in nodal target volumes, and post‐IC nodal volume‐based radiotherapy provides excellent LC in NPC, even in high‐risk LNs.