Prevertebral muscle involvement in nasopharyngeal carcinoma.

PURPOSE: The purpose of this study is to evaluate the prevalence and prognostic significance of prevertebral muscle involvement in patients with nasopharyngeal carcinoma (NPC).

METHODS AND MATERIALS: Between July 1990 and December 2001, 521 newly diagnosed patients with NPC treated at Koo Foundation Sun Yat-Sen Cancer Center (KF-SYSCC) were examined with magnetic resonance imaging (MRI) for evidence of prevertebral muscle involvement before treatment. Patients were staged according to the 1997 American Joint Committee on Cancer staging classification of NPC based on the physical exams and MRI findings. All patients received radiotherapy with or without chemotherapy. The association between clinical prevertebral muscle involvement and posttreatment outcomes (overall survival, locoregional recurrence, and distant metastasis) were evaluated using Cox regression model to adjust for other prognostic factors.

RESULTS

Of 521 patients treated at KF-SYSCC, 181 (35%) patients were found to have prevertebral muscle involvement, one-third in those with Stage II/III tumors and two-thirds in those with Stage IV tumor. In multivariate analysis accounting for all previously known prognostic factors, prevertebral muscle invasion was associated with an increased risk for any recurrence (adjusted relative risk, 2.01; p<0.001), locoregional recurrence (adjusted relative risk, 2.69; p<0.001), and distant metastasis (adjusted relative risk, 2.25; p<0.001), and with a borderline significant increased risk for overall survival (adjusted relative risk, 1.44; p=0.10).

CONCLUSIONS

Prevertebral muscle involvement is an independent prognostic factor for NPC recurrence.