Dosimetric Comparison and Selection Criteria of Intensity-Modulated Proton Therapy and Intensity-Modulated Radiation Therapy for Adaptive Re-Plan in T3-4 Nasopharynx Cancer Patients

• Published in: Cancers 2024-10, Vol.16 (19), p.3402
• Main Authors: Ko, Mincheol, Yang, Kyungmi, Ahn, Yong Chan, Ju, Sang Gyu, Oh, Dongryul, Kim, Yeong-Bi, Kwon, Dong Yeol, Park, Seyjoon, Lee, Kisung
• Format: Article
• Language: English
• Subjects: Brain stem; Cancer therapies; Care and treatment; Comparative analysis; Conformity; Decision making; Diagnosis; Dosimetry; Intensity-modulated radiotherapy; Methods; Nasopharyngeal cancer; Nasopharynx; Nerves; Optic chiasm; Oral cavity; Patients; Proton beam radiotherapy; Protons; Quality of life; Radiation dosimetry; Radiation therapy; Resource utilization; Spinal cord; Tissues; Tomography; Toxicity; Tumors; X-rays
• ISSN: 2072-6694; 2072-6694
• DOI: 10.3390/cancers16193402

Proton therapy requires caution when treating patients with targets near neural structures. Intuitive and quantitative guidelines are needed to support decision-making concerning the treatment modality. This study compared dosimetric profiles of intensity-modulated proton therapy (IMPT) and intensity-modulated radiation therapy (IMRT) using helical tomotherapy (HT) for adaptive re-planning in cT3-4 nasopharyngeal cancer (NPCa) patients, aiming to establish criteria for selecting appropriate treatment modalities. HT and IMPT plans were generated for 28 cT3-4 NPCa patients undergoing definitive radiotherapy. Dosimetric comparisons were performed for target coverage and high-priority organs at risk (OARs). The correlation between dosimetric parameters and RT modality selection was analyzed with the target OAR distances. Target coverages were similar, while IMPT achieved better dose spillage. HT was more favorable for brainstem D , optic chiasm D , optic nerves D , and p-cord D . IMPT showed advantages for oral cavity D . Actually, 14 IMPT and 14 HT plans were selected as adaptive plans, with IMPT allocated to most cT3 patients (92.9% vs. 42.9%, = 0.013). The shortest distances from the target to neural structures were negatively correlated with OAR doses. Receiver operating characteristic curve analyses were carried out to discover the optimal cut-off values of the shortest distances between the target and the OARs (temporal lobes and brainstem), which were 0.75 cm (AUC = 0.908, specificity = 1.00) and 0.85 cm (AUC = 0.857, specificity = 0.929), respectively. NPCa patients with cT4 tumor or with the shortest distance between the target and critical neural structures < 0.8 cm were suboptimal candidates for IMPT adaptive re-planning. These criteria may improve resource utilization and clinical outcomes.