Locoregional extension and patterns of failure for nasopharyngeal carcinoma with intracranial extension.

OBJECTIVE: To evaluate the locoregional extension and patterns of failure for nasopharyngeal carcinoma (NPC) with intracranial extension to improve clinical target volume (CTV) delineation. PATIENTS AND METHODS: A total of 205 NPC patients with intracranial extension by magnetic resonance imaging (MRI) were retrospectively reviewed. RESULTS: According to the cumulative incidence rates of tumor invasion, we initially classified anatomic sites surrounding the nasopharynx into three risk grades: high risk (>/=35%), medium risk (>/=10-35%), and low risk (<10%). It was concluded that the anatomic sites at high risk of tumor invasion were the middle/posterior skull base and the anatomic sites adjacent to the nasopharynx. The rate of lymph node (LN) metastasis was 90.2% (185/205). Retropharyngeal region (RP) and level IIb were the most frequently involved regions. Skip metastasis occurred in only 1.6% (3/185). At their last follow-up visit, 53 patients (25.9%) had developed treatment failure. Of the 18 local failures, 12 were considered in-field failure; the other 5 were marginal; one of the patients had outside-field failure. Among the 5 patients with marginal failures, 4 occurred mainly intracranially, and 1 occurred in the floor and the left lateral wall of the nasopharynx. Of the 11 regional failures, 10 were considered in-field failures and most of them (8/10) occurred in the unilateral upper neck. CONCLUSION: For NPC with intracranial extension, primary disease and regional LN spread follow an orderly pattern and LN skipping was unusual. Clinical target volume reduction may be feasible for selected patients.