Long-term Outcomes of Intensity Modulated Radiation Therapy for T1-T2 Nasopharyngeal Carcinoma

Abstract

To evaluate the efficacy of the treatment for T1-T2 non-metastasis nasopharyngeal carcinoma (NPC) with intensity modulated radiation therapy (IMRT). We retrospectively analyzed 139 NPC patients treated by IMRT between January 2005 and December 2010 in our center, with a sex ratio of 3.2:1 (male 106: female 33). Median age was 49 years (18–73 years). According to the AJCC staging system, there were 16, 55, 38, and 30 patients with stage I, II, III, and IV disease. All patients received treatment with IMRT. Gross tumor volume (GTV) included the primary tumor and metastatic lymph nodes found in clinical and imaging examination. Clinical target volume (CTV) included the nasopharynx, retropharyngeal lymph node, skull base, anterior one-third of the clivus, pterygoid fossa, parapharyngeal space, the inferior sphenoid sinus, posterior one-third of the nasal cavity and the maxillary sinus, and drainage of the upper neck (levels II, III and Va) in N0 patients. In N1–N3 patients, levels II-V were included. The prescription doses were 66 Gy in 30 fractions to the GTV of nasopharynx and the positive neck nodes, 60 Gy to the high-risk CTV, and 54 Gy to the low-risk CTV. All patients were irradiated 1 fraction daily, 5 days per week. Patients staged III, IV A/B, or II (lymph node measured 4 cm or more in diameter) received platinum-based chemotherapy. All patients were evaluated weekly during RT, and every 3 months in the first 2 years after the completion of their treatment, every 6 months for the next 3 years, and annually thereafter. A statistical software package was used for statistical analysis. The Kaplan–Meier method was used to calculate local control (LCR), distant metastasis-free (DMF) and overall survival (OS) rates. With a median follow-up of 59 months (range, 13–98 months), the 5-year OS, LCR, region control, and DMF rates were 87.8%, 96.7%, 94.9%, and 89.1%, respectively. Seven patients had recurrences in the nasopharynx. Seven had recurrences in the regional lymph nodes and 15 had distant metastasis. The 5-year LCR for patients with T1 and T2 diseases were 94.9% and 97.7%, respectively (P=.664). The 5-year DMF rates for patients with N0, N1, N2, and N3 diseases were 95.7%, 100%, 89.5%, and 65.4%, respectively (P=.000). The 5-year OS rates for patients with N0, N1, N2 and N3 diseases were 95.7%, 100%, 79.8%, and 70.5%, respectively (P=.002). The treatment with IMRT for T1-T2 NPC is effective. Distant metastasis was the major reason for treatment failures, distant metastasis rate with N2-3 was prominently higher than N0-1. It is worthy of further studies controlling distant metastasis of the patients with N2-3.