IMRT with simultaneous integrated boost and concurrent chemotherapy for nasopharyngeal cancer: Plan evaluation and treatment outcome

Objective: This study evaluated the outcome of intensity-modulated radiation therapy with simultaneous integrated boost and concurrent chemotherapy for nasopharyngeal cancer. Methods: We analyzed 53 consecutive nasopharyngeal cancer patients who received definitive treatment using intensity-modulated radiation therapy with simultaneous integrated boost and cisplatin-based concurrent chemotherapy. Forty-six patients were treated with concurrent chemoradiation and seven patients with induction chemotherapy plus concurrent chemoradiation. The gross tumor (PTV. ₇₀) received 69.96 Gy (2.12 Gy/fraction), high-risk subclinical disease (PTV. ₆₀) received 59.4 Gy (1.8 Gy/fraction) and low-risk subclinical disease (PTV. ₅₆) received 56.1 Gy (1.7 Gy/fraction) in 33 fractions. Twenty-eight patients were treated with step-and-shoot intensity-modulated radiation therapy and 25 patients with helical tomotherapy. Dosimetric parameters were compared between the two modalities. Results: The median treatment duration was 49 days (range: 41-65 days). The complete response rate was 92.5%. Three local, two regional, one locoregional and seven distant failures were observed. With the median follow-up of 41 months (range: 8-89 months), the 3- and 5-year local control, locoregional control, disease-free survival and overall survival rates were 91.8 and 91.8%; 87.6 and 87.6%; 77.5 and 70.5%; and 86.4 and 82.1%, respectively. Grade 3 mucositis, dermatitis, leucopenia and grade 4 leucopenia were observed in 10, 1, 2 and 1 patient, respectively. No grade 3 or higher xerostomia occurred. Helical tomotherapy significantly improved dosimetric parameters including the maximum dose, volume receiving >107% of the prescribed dose and uniformity index (D₅/D₉₅). Conclusions: Intensity-modulated radiation therapy with simultaneous integrated boost with concurrent chemotherapy is a safe and effective treatment modality for nasopharyngeal cancer. Helical tomotherapy has a dosimetric advantage over step-and-shoot intensity-modulated radiation therapy in a clinical setting.