Prognostic factors of glottic carcinomas treated with radiation therapy: value of the adjacent sign on radiological examinations in the sixth edition of the UICC TNM staging system.

PURPOSE

To evaluate the predictive value of the adjacent sign, the tumor adjacent to the thyroid cartilage on radiologic examinations, in the new sixth edition of the International Union Against Cancer (UICC) staging system of glottic carcinoma.

METHODS AND MATERIALS

Between 1989 and 1998, 130 patients with T1-2N0 glottic squamous cell carcinoma, classified according to the fifth edition of the UICC staging system and evaluated by computed tomography or magnetic resonance imaging, were treated with radiation therapy (RT). Factor analysis included clinical, radiologic, and treatment characteristics. Tumors with the adjacent sign, considered representative of paraglottic space invasion with or without minor thyroid cartilage erosion, were retrospectively classified as T3-stage tumors by the UICC sixth edition.

RESULTS

The 5-year local control rate after RT was 76%. Univariate analysis showed that the T stage according to the UICC fifth edition, supraglottic extension, subglottic extension, tumor size, adjacent sign, total dose, fraction size, field size, and overall treatment time were significant factors for the local control rate. Multivariate analysis confirmed the adjacent sign as the only independent predictor. According to the UICC sixth edition, the 5-year local control, laryngeal preservation, cause-specific survival, and overall survival rates of the T3 (adjacent sign-positive) vs. T1 and T2 (adjacent sign-negative) lesions were 37% vs. 87% (p < 0.0001), 47% vs. 95% (p < 0.0001), 75% vs. 99% (p < 0.0001), and 54% vs. 81% (p = 0.0180), respectively.

CONCLUSION

Factor analysis confirmed the adjacent sign as an independent prognostic factor. The UICC sixth edition appears to identify correctly patients with T3 lesions as a high-risk group.