Intensity-Modulated Radiotherapy for Head and Neck Cancer of Unknown Primary: Toxicity and Preliminary Efficacy

Abstract

Unknown primary head and neck cancers often require comprehensive mucosal and bilateral neck irradiation. With conventional techniques, significant toxicity can develop. Intensity-modulated radiotherapy (IMRT) has the potential to minimize the toxicity. Between 2000 and 2005, 21 patients underwent IMRT for unknown primary head and neck cancer at our center. Of the 21 patients, 5 received IMRT with definitive intent and 16 as postoperative therapy; 14 received concurrent chemotherapy and 7 IMRT alone. The target volumes included the bilateral neck and mucosal surface. The median dose was 66 Gy. Acute and chronic toxicities, esophageal strictures, and percutaneous endoscopic gastrostomy tube dependence were evaluated. Progression-free survival, regional progression-free survival, distant metastasis-free survival, and overall survival were estimated with Kaplan-Meier curves. With a median follow-up of 24 months, the 2-year regional progression-free survival, distant metastasis-free survival, and overall survival rate was 90%, 90%, and 85%, respectively. Acute grade 1 and 2 xerostomia was seen in 57% and 43% of patients, respectively. Salivary function improved with time. Percutaneous endoscopic gastrostomy tube placement was required in 72% with combined modality treatment and 43% with IMRT alone. Only 1 patient required percutaneous endoscopic gastrostomy support at the last follow-up visit. Two patients treated with combined modality and one treated with IMRT alone developed esophageal strictures, but all had improvement or resolution with dilation. The preliminary analysis of IMRT for unknown primary head and neck cancer has shown acceptable toxicity and encouraging efficacy. The analysis of the dosimetric variables showed excellent tumor coverage and acceptable doses to critical normal structures. Esophageal strictures developed but were effectively treated with dilation. Techniques to limit the esophageal dose could help further minimize this complication.