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New staging system for nasopharyngeal carcinoma. Long-term outcome.

We report prognostic determinants and survival found after a long follow-up of 182 patients in North America in a prospective collaborative study. All patients were under observation since enrollment, and all were treated with modern equipment and techniques at major medical centers. Use of Cox regression methods identified five disease-related characteristics significantly associated with survival. These form the basis of the new staging system. A second system including antibody-dependent cellular cytotoxicity was developed because a high antibody-dependent cellular cytotoxicity titer correlated with good prognosis. The two new systems are better predictors of outcome than are the traditional staging systems. The unique World Health Organization 2 and 3 morphologic forms of nasopharyngeal carcinoma appear to be chronic diseases, because the risk of death does not level off with time, as it does for most other cancers.