Changes in lactate dehydrogenase isoenzymes associated with relapse of childhood acute lymphocytic leukemia

Twenty-eight children with high-risk acute lymphocytic leukemia underwent monthly serum lactate dehydrogenase (LDH) and LDH isoenzyme fraction determinations to examine whether LDH isoenzyme fractions change with an increase in the body burden of tumor cells. The 9 patients who relapsed and 5 patients who presented with leukemia during the study period had a slightly lower mean LDH-1 isoenzyme fraction. When the period from 3 months before to 3 months after relapse was examined, significant increases in the LDH-3 isoenzyme fraction and decreases in the LDH-1 and LDH-2 isoenzyme fractions were seen at the time of relapse. These results were highly significant when patients with non-T-cell and T-cell leukemia were combined and when bone marrow and central nervous system relapse was included. The changes at relapse appeared to revert with intensification of chemotherapy. The changes at relapse were not different in magnitude from random variation occurring in patients who remained in remission throughout the study. Although changes in LDH isoenzymes appeared to occur at the time of relapse compared with the periods immediately before and after relapse, these changes were not specific for relapse. LDH isoenzymes do not appear to be useful in predicting relapse in children with leukemia.