Supplementary Material for: A prospective study on defining the indications of prophylactic level IB radiotherapy in nasopharyngeal carcinoma based on a risk score model

Objective: To investigate clinical evidence for defining the indications of prophylactic level IB radiotherapy in nasopharyngeal carcinoma (NPC).
Methods: We conducted a phase 2 prospective study in 116 newly diagnosed patients with NPC treated by intensity-modulated radiotherapy (IMRT). Whether level IB was irradiated based on the risk score model (RSM). Two groups based on RSM were obtained: low risk and high risk. Omission of level IB irradiation was conducted in low risk group, otherwise level IB was contoured as part of the treatment target. Grade 2 or worse xerostomia at 12 months was assessed by the European Organization for Research and Treatment of Cancer (EORTC) QLQ-H&N35 questionnaire.
Results: At a median follow-up of 16months (range, 1-26 months). None patients developed failures at level IB. The 1-year overall survival (OS), locoregional recurrence-free survival (LRRFS) and distant metastasis-free survival (DMFS) rates were 98.3%, 97.2% and 95.8%, respectively. At 12 months xerostomia side-effects were reported 90 of 126 alive patients, grade 2 or worse xerostomia at 12 months was significantly lower in the low risk group than in the high risk group.
Conclusion: Omission of level IB irradiation was feasible for patients with low-risk IB lymph nodes metastasis.