3678 - Preliminary Evaluation of HyperArc Stereotactic Body Radiotherapy for Local Recurrent Nasopharyngeal Cancer: Do Dosimetric Advantages Translate into Therapeutic Benefits?

Y. W. Lin¹, C. C. Yang², and H. W. Ho²; ¹Department of Radiation Oncology, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan, ²Department of Radiation Oncology, Chi Mei Medical Center, Tainan, Taiwan

Purpose/Objective(s): Investigate the efficacy and safety of HyperArc Stereotactic Body Radiotherapy (HA-SBRT) in managing local recurrent nasopharyngeal cancer (NPC), focusing on treatment outcomes and toxicities. Materials/

Methods: A prospective clinical study was conducted, enrolling patients with local recurrent NPC treated with HyperArc Stereotactic Body Radiotherapy (HA-SBRT) between December 2018 and May 2022. All patients had previously undergone radiation treatment (prescribed doses: 69.96 to 72 Gy) and failed initial intensity-modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT). Salvage doses of 30-40 Gy were administered every other day for 5 fractions, with concurrent cisplatin-based chemotherapy. Treatment-related toxicities, disease responses, and survival rates were prospectively monitored and assessed.
Results: The study recruited 7 patients with local recurrent NPC. The recurrent stages were cT1 (4 patients), cT2 (1 patient), or cT4 (2 patients); the recurrent tumor volumes ranged from 2.4 to 37.1 cm3. Median follow-up time was 23.5 months. All patients completed HA-SBRT without significant acute toxicities. Six patients achieved complete regression of recurrent tumors, with one patient exhibiting local residual disease. Two-year disease-free and overall survival rates were 85.7% and 71.4%, respectively. However, two patients experienced late complications (grade 2 radiation-induced mucosal necrosis), and one patient died from massive hemorrhage (grade 5).
Conclusion: HA-SBRT demonstrates promise in managing local recurrent NPC, offering precise delivery and adherence to chemotherapy. Further research is warranted to optimize dose and fractionation, aiming to maintain high response rates while minimizing late toxicities.