Dynamic helical CT of T1 and T2 glottic carcinomas: Predictive value for local control with radiation therapy

BACKGROUND AND PURPOSE: Tumor volume and cartilage invasion have been sugge sted as prognostic factors of glottic carcinomas following definitive radia tion therapy. Radiologic examinations provide additional information regard ing the deep extension of tumor. We determined whether dynamic helical CT c an predict local control of early (T1 and T2 stage) glottic carcinomas trea ted with definitive radiation therapy. METHODS: Sixty-eight patients with early glottic carcinoma evaluated on pre treatment dynamic helical CT were treated with definitive radiation therapy . Tumor detectability, maximum dimension, tumor volume, and involvement of anatomic subsites (anterior commissure, ventricle, subglottic region, and t hyroid and arytenoid cartilages) were determined by consensus by three radi ologists without previous knowledge of the clinical information. The CT fin dings were correlated with local control. RESULTS: The two-year local control rate was 76%; 91% for T1 and 60% for T2 lesions, Univariate analysis revealed clinical T stage, tumor detectabilit y, maximum dimension, tumor volume, anterior commissure involvement, ventri cle involvement, and thyroid cartilage involvement as significant prognosti c factors. Thyroid cartilage involvement was an independent predictor by mu ltivariate analysis. The lesions separate from the thyroid cartilage had a 95% probability of local control, whereas the lesions adjacent to the carti lage had only a 42% control rate. CONCLUSION: Dynamic helical CT provides prognostic information for the resu lts of definitive radiation therapy. Patients with a tumor adjacent to the thyroid cartilage had an increased risk of local failure.