2872 - Vertebral Artery-Sparing IMPT for Patients with Nasopharyngeal Carcinoma- Dosimetry and Clinical Outcomes.
Presenter(s)
Y. M. Wang1, Y. H. Lin1, B. S. Huang1, W. C. Lin2, P. J. Juang1, M. W. Ho3, E. Y. Huang1, S. H. Li4, and S. D. Luo5; 1Proton and Radiation Therapy Center, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan, 2Department of Diagnostic Radiology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan, 3New York Proton Center, New York City, NY, 4Department of Hematology-Oncology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan, 5Department of Otolaryngology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan
Purpose/Objective(s): Radiotherapy is a cornerstone in the treatment of nasopharyngeal carcinoma (NPC); however, its impact on vascular structures, particularly the vertebral arteries, can contribute to arterial stenosis, increasing the risk of ischemic stroke and neurological complications. Vertebral artery-sparing intensity-modulated proton therapy (VAS-IMPT) has been developed to optimize dose distribution, effectively reducing radiation exposure to these arteries while preserving therapeutic coverage. This study presents the clinical outcomes and dosimetric advantages of VAS-IMPT in NPC patients treated at our institution.
Materials/Methods: This retrospective review included consecutive newly diagnosed NPC patients who underwent VAS-IMPT between 2021 and 2023. All patients received a total prescribed dose of 69.96 Gy(RBE) in 33 fractions to the primary tumor and involved lymph nodes, with simultaneously prophylactic bilateral neck irradiation. Treatment was combined with systemic chemotherapy according to institutional protocols. Adverse effects were graded using the Common Terminology Criteria for Adverse Events (CTCAE), while overall survival, local control, and regional control were assessed using Kaplan-Meier analysis. In addition, the radiation dose to the vertebral and basilar arteries was quantified to evaluate the potential vascular-sparing benefits.
Results: A total of 60 NPC consecutive patients underwent VAS-IMPT. Based on the AJCC 8th edition staging system, the cohort included 8 Stage I, 8 Stage II, 22 Stage III, and 22 Stage IV patients. Dosimetric analysis confirmed that the mean radiation dose to the vertebral arteries was 37.4 Gy(RBE), while the basilar artery received an average dose of 35.4 Gy(RBE), demonstrating the effectiveness of this technique in sparing critical vascular structures. Treatment was well tolerated, with only 6 patients (10%) developing mucositis of Grade 2 or higher and 3 patients (5%) experiencing Grade 3 radiation dermatitis; none required nasogastric or any feeding tube placement. After a median follow-up of 30 months, all patients remained alive, with 3-year local control of and overall survival at 100%. Only one patient, initially diagnosed with extensive nodal disease (N3), exhibited persistent lymphadenopathy, which was successfully managed with salvage neck dissection.
Conclusion: Our findings suggest that VAS-IMPT provides excellent tumor control while significantly reducing radiation dose to the vertebral arteries, which may help lower the risk of long-term cerebrovascular complications. This approach demonstrates a favorable toxicity profile without compromising treatment efficacy. While extended follow-up is necessary to confirm the durability of these benefits, VAS-IMPT represents a promising strategy for NPC patients. A detailed analysis of arterial dose distributions and clinical outcomes will be presented at the meeting.