Assessment of complete remission after 2-chlorodeoxyadenosine for hairy cell leukemia: utility of marrow immunostaining and measurement of splenic index.

2-Chlorodeoxyadenosine (2-CdA) yields high complete remission (CR) rates in patients with hairy cell leukemia (HCL) Two approaches were used to detect minimal residual disease. We studied two B-lineage antibodies, L26 and MB2, and a T-lineage antibody, UCHL-1, in fixed marrow core biopsies from 34 patients with HCL before and after 2-CdA to detect minimal residual in the marrow. In addition, the splenic index was calculated before and after treatment to detect residual splenomegaly. Prior to therapy, hairy cells exhibited intense cytoplasmic membrane reactivity with L26 and strong intracytoplasmic reactivity with MB2. UCHL-1 did not react with hairy cells. Thirty-one patients were assessable 3 months after therapy. Five of 24 (21%) patients in CR by routine evaluation had residual HCL detected by immunostaining. Four of these 5 patients have been reevaluated at 1 year. One patient relapsed by routine evaluation, 2 remained positive by immunostaining alone, and 1 patient became negative by immunostaining. A total of 19 patients have been evaluated at 1 year and 17 remain in CR. Three of these 17 were positive by immunostaining, 2 of whom had been positive at 3 months and 1 additional patient who became positive by immunostaining at 1 year. Of 9 patients evaluated at 2 years, an additional 2 of 3 patients with minimal residual disease detected previously by immunostaining at 3 months relapsed by routine morphology and 1 had persistent positive immunostaining. Only 1 patient in remission by morphology and immunostaining has relapsed.(ABSTRACT TRUNCATED AT 250 WORDS)