Epstein-Barr virus-related lymphocyte stimulation inhibitor: a possible prognostic tool for undifferentiated nasopharyngeal carcinoma.

It is demonstrated in this study that a serum factor, a lymphocyte stimulation inhibitor (LSI), which inhibits Epstein-Barr virus (EBV)-induced lymphocyte stimulation, is a potentially useful tool in the diagnosis and monitoring of nasopharyngeal carcinoma (NPC). In a study of 25 patients with undifferentiated NPC, 20 healthy controls, and 20 patients with other head and neck tumors, LSI was found only in the NPC patients with active disease. In a more complete study of 8 patients longitudinally followed up for at least 20 months, a comparison of LSI with antibodies to a variety of EBV antigens including viral capsid antigen, early antigen, and nuclear antigen indicated that LSI levels provided a reliable and sensitive indicator of disease activity that should be added to clinical markers currently in use as monitors of disease activity in NPC.