Intermittent chemotherapy and immunotherapy with BCG in remission maintenance of children with acute lymphocytic leukemia: Effects upon immunological function

Twelve children with acute lymphocytic leukemia who had been in complete remission on continuous chemotherapy for at least 12 months, were treated with intermittent courses of chemotherapy alternating with BCG inoculation during the drug-free intervals. Measurements were made of leukocyte populations in blood and bone marrow leukemic blastogenic responses of blood lymphoid cells to phytohemmagglutinin and soluble leukemic blast cell membrane antigen. Antibody titers to a soluble leukemic blast-cell membrane-derived antigen were determined. Comparison was made with similar measurements during a second phase of intermittent chemotherapy without BCG inoculation (phase II). Two children showed bone-marrow relapse and two developed central nervous system leukemia during the study. Rises in blood and bone-marrow lymphoid cell numbers were found during both phases of the study. Blastogenic responses to phytohemagglutinin, depressed at the start of the study following at least 12 months of continuous chemotherapy, rose during intermittent chemotherapy and BCG and remained within normal ranges during phase II. Antibody titers and blastogenic responses to leukemia blast-cell membrane antigens increased in eight of twelve and six of seven children respectively during the BCG phase and were maintained during phase II. Only one child showed further increases in phase II. The combination of BCG and intermittent chemotherapy may increase leukemia-associated immunity in some patients with acute lymphocytic leukemia in remission. The separate contributions of either BCG or intermittent chemotherapy in producing this effect cannot be determined by this study.