Antibody-Dependent Cellular Cytotoxicity: Relation to Stage and Disease Course in North American Patients With Nasopharyngeal Carcinoma

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Abstract
A prospective study of North American patients, mostly white, with different histopathologic types of nasopharyngeal carcinoma was initiated approximately five years ago. Several anti-Epstein-Barr virus (EBV) serologic tests are being evaluated; one is the antibody-dependent cellular cytotoxicity (ADCC) assay, which measures antibodies to an EBV-induced membrane antigen component. A low ADCC titer at diagnosis reflects a poor prognosis, and the determination of antibody titers by this assay identifies patients in whom recurrent disease is likely to develop after conventional radiation therapy for World Health Organization types 2 and 3 carcinomas. Of the patients who had high ADCC titers at diagnosis, 80% survived three years or longer, whereas 50% of the patients with low titers survived three years, and only 35% survived five years. High and low ADCC titers were seen in all stages (except in Ho stage V), and the distribution of patients by high and low ADCC titers was similar in each of the stage groupings. We conclude that the ADCC titer at the time of diagnosis is generally predictive of the prognosis. Clinical staging is the traditional approach for predicting prognosis, but determination of the ADCC titer can be used to segregate patients within the stage groups into those with "good" and "poor" prognoses. Serologic testing may eventually become one of the methods for staging patients with WHO types 2 and 3 nasopharyngeal carcinoma.