Postoperative Radiotherapy in Malignant Tumors of the Parotid Gland

Chung, Woong Ki; Ahn, Sung Ja; Nam, Taek Keun; Chung, Kyung Ae; Nah, Byung Sik

Abstract

PURPOSE: This study was performed to analyze the factors affecting local control in malignant tumors of the parotid gland treated with surgery and postoperative radiation.
MATERIALS AND METHODS
Twenty-six patients were treated for malignant tumors of the parotid gland from 1986 to 1995 at Department of Therapeutic Radiology, Chonnam University Hospital. Age of the patients ranged from 14 to 72 years (median : 55 years). Histologically 10 patients of mucoepidermoid carcinoma, 7 of squamous cell carcinoma, 4 of acinic cell carcinoma, 4 of adenoid cystic carcinoma and 1 of adenocarcinoma were treated. Total parotidectomy was performd in 15 of 26 patients, superficial in 7, subtotal in 4. Facial nerve was sacrificed in 5 patients. Postoperatively 4 patients had residual disease, 4 had positive resection margin. Radiation was delivered through an ipsilateral wedged pair of photon in 11 patients. High energy electron beam was mixed with photon in 15 patients. Electron beam dose ranged from 900 cGy to 3800 cGy (median : 1760 cGy). Total radiation dose ranged from 5000 cGy to 7560 cGy (median : 6020 cGy). Minimum follow-up period was 2 years. Local control and survival rate were calculated using Kaplan-Meier method. Generalized Wilcoxon test and Cox proportional hazard model were used to test factors affecting local control.
RESULTS
Five (19%) of 26 patients had local recurrence. Five year local control rate was 77%. Overall five year survival rate was 70%. Sex, age, tumor size, surgical involvement of cervical lymph node, involvement of resection margin, surgical invasion of nerve, and total dose were analyzed as suggested factors affecting local control rate. Among them patients with tumor size less than 4 cm (p=0.002) and negative resection margin (p= 0.011) were associated with better local control rates in univariate analysis.Multivariate analysis showed only tumor size factor is associated with local control rate (p=0.022).
CONCLUSION
This study suggested that tumor size is important in local control of malignant tumors of parotid gland.