Improved dosimetric and clinical outcomes with intensity-modulated radiotherapy for head-and-neck cancer of unknown primary origin.

PURPOSE To compare differences in dosimetric, clinical, and quality-of-life endpoints among a cohort of patients treated by intensity-modulated radiotherapy (IMRT) and conventional radiotherapy (CRT) for head-and-neck cancer of unknown primary origin. METHODS AND MATERIALS The medical records of 51 patients treated by radiation therapy for squamous cell carcinoma of the head and neck presenting as cervical lymph node metastasis of occult primary origin were reviewed. Twenty-four patients (47%) were treated using CRT, and 27 (53%) were treated using IMRT. The proportions of patients receiving concurrent chemotherapy were 54% and 63%, respectively. RESULTS The 2-year estimates of overall survival, local-regional control, and disease-specific survival for the entire patient population were 86%, 89%, and 84%, respectively. There were no significant differences in any of these endpoints with respect to radiation therapy technique (p>0.05 for all). Dosimetric analysis revealed that the use of IMRT resulted in significant improvements with respect to mean dose and V30 to the contralateral (spared) parotid gland. In addition, mean doses to the ipsilateral inner and middle ear structures were significantly reduced with IMRT (p<0.05 for all). The incidence of severe xerostomia in the late setting was 58% and 11% among patients treated by CRT and IMRT, respectively (p<0.001). The percentages of patients who were G-tube dependent at 6 months after treatment were 42% and 11%, respectively (p<0.001). CONCLUSIONS IMRT results in significant improvements in the therapeutic ratio among patients treated by radiation therapy for head-and-neck cancer of unknown primary origin.