Prognostic Factors for Local Control in Early Glottic Cancer Treated with Radiation Therapy

Chung, Woong Ki; Ahn, Sung Ja; Nam, Taek Keun; Nah, Byung Sik; Cho, Jae Shik; Lim, Sang Chull

Abstract

PURPOSE
This study was performed to find out the prognostic factors affecting local control in early glottic cancer treated with radiation therapy alone.
MATERIALS AND METHODS
We analysed 37 patients of histologically confirmed early glottic cancer treated at Chonnam National University Hospital between July 1986 and December 1995, retrospectively. Age of patients ranged from 30 to 73 years (median; 59 years). Thirty-five (95%) patients were male. Histological type was all squamous cell carcinoma. According to the staging system of 1997 American Joint Committee on Cancer, 37 patients were restaged as follows: T1a; 27 (73%), T1b; 3 (8%), T2; 7 (19%). Radiation therapy was done using 6 MV X-ray of linear accelerator. The range of total radiation dose delivered to the glottic lesion was between 5,040 cGy and 7,020 cGy (median; 6,600 cGy). Median follow-up period was 80 months. Local control rates were calculated by Kaplan-Meier method. Generalized Wilcoxon test was used to evaluate the difference of control rates between comparable groups. Multivariate analysis using Cox proportional hazard model was done to find out prognostic factors affecting local control.
RESULTS
5 year survival rate of 37 patients was 89%. Local control rate of 37 patients was 74% in 5 years. We included age, T-stage, anterior commissure involvement, fraction size, total radiation dose, treatment time of radiotherapy as potential prognostic factors in univariate and multivariate analysis. As a result, treatment time had statistical significance in local control rate in both univariate ( p=0.026) and multivariate ( p=0.017) analysis. Complication was not recorded except one patient with hypothyroidism.
CONCLUSION
This study revealed that overall treatment time of radiation was a significant factor affecting local control rate.