Objective: To evaluate the toxicity and clinical efficacy of simultaneous modulated accelerated radiation therapy (SMART) technique for nasopharyngeal carcinoma.
Methods: 110 patients with nasopharyngeal carcinoma underwent boost treatment with SMART at the dose of 2.5 Gy/time for 28 times for gross tumor volume (GTV) with the total dose of 70 Gy and the dose of 2.0 Gy/time once a day and 5 times a week, totally 28 times, with the total dose of 56 Gy for the clinical treatment volume (CTV). The GTV dose for 36 of these patients was boosted to 80 Gy. Follow-up was conducted for 24 months (7 - 44 months).
Results: Follow-up showed that the 1, 2, and 3-year survival rates were 97.02%, 88.72%, and 78.27%, respectively. The 1 - 3 year local relapse-free survival rate was 97.94% (95.10% - 100%). The 1, 2, and 3-yea local-regional relapse-free rates and distant metastasis-free rates were 95.21%, 89.83%, 76.10% and 95.38%, 85.71%, and 79.67%, respectively. According to the Fuzhou staging, the 3-year overall survival rate of the stage I - II patients was 100%, while the 3-year survival rate of the stage III patients was 74.33% and the 3-year survival rate of stage IV a patients was 62.96%. The acute toxicity was well tolerated except for the high incidence of severe mucositis. No grade 4 side effects occurred. Most of the patients showed Grade 0 to 1 late toxicity and xerostomia was a common side effect. No increase of toxicity was seen when the GTV dose was increased to 80 Gy.
Conclusion: SMART yields superior dose distribution over the traditional radiotherapy in nasopharyngeal carcinoma at the early or advanced stages. The local-regional control was excellent and distant metastasis remains the main risk. Dose escalation to 80 Gy was safe and feasible. Toxicity of SMART is acceptable and tolerable.