Background and purpose: Tumor volume and cartilage invasion have been suggested as prognostic factors of glottic carcinomas following definitive radiation therapy. Radiologic examinations provide additional information regarding the deep extension of tumor. We determined whether dynamic helical CT can predict local control of early (T1 and T2 stage) glottic carcinomas treated with definitive radiation therapy.
Methods: Sixty-eight patients with early glottic carcinoma evaluated on pretreatment 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 thyroid and arytenoid cartilages) were determined by consensus by three radiologists without previous knowledge of the clinical information. The CT findings 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 detectability, maximum dimension, tumor volume, anterior commissure involvement, ventricle involvement, and thyroid cartilage involvement as significant prognostic factors. Thyroid cartilage involvement was an independent predictor by multivariate analysis. The lesions separate from the thyroid cartilage had a 95% probability of local control, whereas the lesions adjacent to the cartilage had only a 42% control rate.
Conclusion: Dynamic helical CT provides prognostic information for the results of definitive radiation therapy. Patients with a tumor adjacent to the thyroid cartilage had an increased risk of local failure.