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

Abstract

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.

fig 1.

A 68-year-old man with glottic carcinoma of the right true cord (T2 stage). This patient was curatively treated with radiation therapy. Dynamic helical CT shows an enhanced mass in the right true cord with a volume of 545 mm³ (arrow). The thyroid cartilage is intact.fig 2. A 71-year-old man with glottic carcinoma of the left true cord (T2 stage). This patient had a local recurrence after radiation therapy. Dynamic helical CT shows an enhanced mass in the left true cord with a volume of 871 mm³ (arrows). The tumor is adjacent to the left thyroid cartilage with irregular cortex.fig 3. A 68-year-old man with an anterior commissure tumor (T2 stage). This patient was curatively treated with radiation therapy. Dynamic helical CT shows an enhanced area in the anterior third of the bilateral true cords with a volume of 152 mm³ (arrows). The lesion involves the anterior commissure, but the thyroid cartilage is intact.fig 4. A 51-year-old man with an anterior commissure tumor (T2 stage). This patient had a local recurrence after radiation therapy. Dynamic helical CT shows an enhanced mass of the bilateral true cords with a volume of 429 mm³ (arrows). The tumor is adjacent to the anterior half of the left thyroid cartilage with irregular cortex (arrowhead)