Changes of plasma EBV DNA during treatment of NK cell lymphomas. (A) A case of nasal NK cell lymphoma. An initial response to chemotherapy was followed by a rapid drop of EBV DNA to undetectable levels. However, with disease relapse, there was a resurgence of EBV DNA. The patient did not respond to treatment, and EBV DNA remained elevated until death. (B) A case of nonnasal NK cell lymphoma. Initial response to treatment was followed by a fall in EBV DNA. With relapse, there was increase in EBV DNA. Although there was a brief response with undetectable EBV DNA, a relapse associated with elevation of EBV DNA occurred, finally leading to death. Mini-BEAM indicates carmustine, etoposide, cytosine arabinoside, melphalan; CVP, cyclophosphamide, vincristine, prednisolone; COPP, cyclophosphamide, vincristine, procarbazine, prednisolone; RT, radiotherapy; NOPP, mitoxantrone, vincristine, procarbazine, prednisolone; and +, death.