ABSTRACT
Objective:To evaluate the effect of reducing clinical target volume (CTV) on local control and overall survival in postoperative intensity-modulated radiotherapy (IMRT), and analyze the patterns of failure, aiming to provide clinical basis for postoperative IMRT delineation of CTV for parotid gland cancer in the era of precision radiotherapy.Methods:Clinical data of 126 patients who were pathologically diagnosed with parotid gland cancer and treated with parotidectomy as well as postoperative radiotherapy were retrospectively analyzed. All patients were divided into two groups according to the prozone of CTV. It was delineated to the anterior border of parotid gland in group A, and delineated to the anterior border of masseter in group B. Actuarial estimates of local recurrence-free survival, regional recurrence-free survival, distant metastasis-free survival and overall survival were obtained with the Kaplan-Meier method. Univariate prognostic analysis was performed by log-rank test. Multivariate prognostic analysis was conducted by Cox regression model.Results:The 5-year local recurrence-free survival (LRFS), regional recurrence-free survival (RRFS), distant metastasis-free survival (DMFS) and overall survival (OS) in groups A and B were 96.7% vs. 91.3%, 96.7% vs. 90.2%, 86.9% v s. 81.3% and 86.0% vs. 81.4%, respectively. There were no significant differences in these parameters between two groups. Of 126 patients with parotid carcinoma, 7 had local recurrence. There were 2 cases in group A which 1 recurred in-field and 1 recurred out- field. And there were 5 cases in group B which 4 recurred in-field and 1 recurred marginally. Univariate analysis showed that age was associated with LRFS. Age, N stage and pathological grading were associated with OS. Cox multivariate analysis revealed that age, N stage and pathological grading were the independent influencing factors of OS. Conclusions:Reducing the CTV would not increase the risk of local recurrence in patients with parotid gland carcinoma without tumor extravasation and negative surgical margins. There is no significant difference in survival benefit compared to those delineated to the anterior border of the masseter muscle. The delineation of CTV should be treated differently according to the risk factors.