ASSESSMENT OF COMPLETE REMISSION AFTER 2-CHLORODEOXYADENOSINE FOR HAIRY-CELL LEUKEMIA - UTILITY OF MARROW IMMUNOSTAINING AND MEASUREMENT OFSPLENIC INDEX

2-Chlorodeoxyadenosine (2-CdA) yields high complete remission (CR) rat es in patients with hairy cell leukemia (HCL) Two approaches were used to detect minimal residual disease. We studied two B-lineage antibodi es, L26 and MB2, and a T-lineage antibody, UCHL-1, in fixed marrow cor e biopsies from 34 patients with HCL before and after 2-CdA to detect minimal residual in the marrow. In addition, the splenic index was cal culated before and after treatment to detect residual splenomegaly. Pr ior to therapy, hairy cells exhibited intense cytoplasmic membrane rea ctivity 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 ev aluation had residual HCL detected by immunostaining. Four of these 5 patients have been reevaluated at 1 year. One patient relapsed by rout ine evaluation, 2 remained positive by immunostaining alone, and 1 pat ient became negative by immunostaining. A total of 19 patients have be en evaluated at 1 year and 17 remain in CR. Three of these 17 were pos itive by immunostaining, 2 of whom had been positive at 3 months and 1 additional patient who became positive by immunostaining at 1 year. O f 9 patients evaluated at 2 years, an additional 2 of 3 patients with minimal residual disease detected previously by immunostaining at 3 mo nths relapsed by routine morphology and 1 had persistent positive immu nostaining. Only 1 patient in remission by morphology and immunostaini ng has relapsed. The splenic index returned to normal in only 1 patien t post-therapy despite normalization of the spleen by craniocaudal dim ension measured by CT scan. These studies suggest that a minority of p atients in CR by conventional criteria after 2-CdA may have minimal re sidual disease in the marrow detected by immunostaining. In contrast, despite resolution of splenomegaly in craniocaudal dimension by CT sca n, persistent splenomegaly as measured by the splenic index was presen t in virtually every patient. Whether or not the identification of min imal residual disease by either marrow immunostaining or persistent sp lenomegaly as determined by the splenic index will be predictive of re lapse and identify a subset of patients warranting additional therapy will require prospective long-term follow-up.