Purpose: To evaluate the efficacy of intensity-modulated radiotherapy (IMRT) using reduced clinical target volumes (CTV) in the treatment of nasopharyngeal carcinoma (NPC).
Methods and materials: Between August 2003 and December 2006, 323 patients with NPC were treated with IMRT according to this institutional protocol. Presenting stages were Stage II in 63, Stage III in 166, and Stage IVA/B in 94 patients. High-risk CTV encompassed gross tumor volume and entire nasopharyngeal mucosa with a margin. A reduced CTV was delineated for the remaining subclinical regions adjacent to the primary disease. Uninvolved neck nodes were delineated according to the Radiation Therapy Oncology Group (RTOG)/European Organisation for Research and Treatment of Cancer (EORTC) consensus excluding the deep jugular (i.e., lymph nodes in retrostyloid space above C1 vertebra) and submental nodes. Patients with locoregionally advanced diseases also received cisplatin-based chemotherapy.
Results: With a median follow-up of 30 months (range, 4-53 months), 12, 6, and 26 patients had developed local, regional, and distant failures, respectively. The 3-year estimated local control, regional control, metastasis-free survival, disease-free survival and overall survival were 95%, 98%, 90%, 85%, and 90%, respectively. Multivariate analyses revealed that T-classification had no predictive value for outcome, whereas N-classification was significant for predicting metastasis-free (p = 0.005) and overall survival (p =0.006). Ten patients (7.8%) experienced Grade II xerostomia at 24 months after treatment. No Grade III or IV late-toxicities were observed. Two patients died of treatment-induced complications.
Conclusion: The IMRT approach using a reduced target volume provided favorable outcome for NPC with acceptable toxicity. This strategy needs to be optimized and then tested in a prospective setting to learn whether further improvement can be achieved.