2.1. Patients

The study population consisted of the patients in the previous matched-comparison NPC study treated with IMPT or VMAT that were treated between 2014 and 2018 [22]. Among these patients, those with incomplete follow-up imaging studies, tumor recurrence with adjuvant therapy, follow-ups of less than 2 years, history of functional endoscopic sinus surgery for CRS, and pre-treatment sinusitis (L–M scores ≥ 4) were excluded (Figure 1). In total, 53 patients in the IMPT group and 54 patients in the VMAT group were enrolled for analysis. All the patients received a standard protocol comprising a physical examination, nasopharyngoscopy, MRI of the head and neck region, and a whole-body tumor scan. The 8th edition of the American Joint Committee on Cancer (AJCC) staging system for NPC was applied for disease staging.

Flow chart of patient selection process.