Intensity-modulated Radiation Therapy in Treating Unknown Primary Head and Neck Cancer: Single Institute Experience

Abstract

Purpose: To retrospectively review the results of patients with metastatic squamous cell carcinoma of the head and neck (SCCHN) from an unknown primary site (UPS) treated with intensity-modulated radiation therapy (IMRT) in a single institute.Methods and Materials: Fourteen male patients with a median age of 48 (range 33 to 67) who presented with unknown primary SCCHN were treated with IMRT with or without cisplatin-based chemotherapy from 2005 to 2010. The number of patients with initial presentation of N1, N2a, N2b and N3 was, 1 (7%), 3 (21%), 6 (43%) and 4 (29%), respectively. Twelve patients (86%) received neck dissections and two had excision biopsies only. Five patients (36%) had metastatic nodes involving both upper and lower neck, where 9 (64%) had nodes limited to the upper neck only. Five (36%) patients presented with extracapsular spread (ECS). Patients undergoing neck dissection were treated with a median dose of 66 Gy to the ECS surgical bed. Those who did not undergo neck dissection were given 60 Gy. For those who had only excision biopsy, 70 Gy was prescribed to the tumor bed and suspected Iymphadenopathy. For all patients, a median dose of 59.4 Gy and 50 Gy was given to the pharyngeal mucosa and uninvolved lower neck, respectively. The irradiated pharyngeal mucosa, included the nasopharynx, oropharynx, surpaglottis and upper hypopharynx, but spared the vocal cords and lower hypopharynx.Results: After a median follow up of 36.4 months, four patients (21%) developed distant metastases and died, yielding a 3-year overall survival rate of 79%. There was no occurrence of the occult primary and no local regional recurrence noted. The control rate was 100%. Two patients had second primary tumors noted over the cervical esophagus and the buccal mucosa. In subgroup analysis, patients with clinical N3 stage, with nodal involvement over the lower neck region and nodes possessing ECS had significantly poorer overall survival and poor distant metastases-free survival rates. In patients with cN2 or cN3 disease, those receiving excision biopsy had a poor overall survival (p=0.001) and distant metastases-free survival (p=0.029) compared to those undergoing neck dissection. There was no grade III chronic toxicity during follow-up.Conclusions: In our experience, IMRT with vocal cords and lower hypopharyngeal sparing can achieve excellent functional outcomes without compromising disease control and may be adopted as a safe and effective treatment for SCCHN of UPS Patients with clinical N3 stage, lower neck involvement and nodes with ECS have significantly poorer overall survival and distant metastases-free survival rates. More intense regimens should be developed for such patients.