Acute nonlymphocytic leukemia, preleukemia, and acute myeloproliferative syndrome secondary to treatment of other malignant diseases. II. Bone marrow cytology, cytogenetics, results of HLA typing, response to antileukemic chemotherapy, and survival in a total series of 55 patients.

Secondary acute nonlymphocytic leukemia or its earlier stages, preleukemia or an acute myeloproliferative syndrome with refractory cytopenia and clonal cytogenetic abnormalities of the bone marrow, was diagnosed in 55 patients previously treated for other malignant diseases. In patients with overt leukemia, cytologic, and cytochemical studies showed predominance of the French-American-British (FAB) type M2. Cytogenetic examination demonstrated a normal karyotype in 11 cases, whereas clonal abnormalities were observed in 44 patients. Defects of chromosome 7 were observed in 24 cases, most often -7, and defects of chromosome 5 in 14 cases, most often 5q-. In addition, chromosomes 3 and 17 were possibly nonrandomly involved. Other abnormalities commonly observed in de novo acute nonlymphocytic leukemia as t(8;21) and t(15;17) were not observed and +8 rarely seen in secondary leukemia. The survival from the leukemic complication was short for the whole group of 55 patients (median, 7 months). However, a significantly longer survival was observed in a subgroup of 11 patients with a normal karyotype (P less than 0.01), due to a favorable response to antileukemic chemotherapy, and in a subgroup of 11 patients with -7 or -C as the only cytogenetic abnormality (P less than 0.01), due to a prolonged preleukemic phase, compared with the remaining 33 cases with mostly multiple karyotypic abnormalities. Three preleukemic patients with -7 who were studied during transformation to overt leukemia all developed additional cytogenetic abnormalities. According to the two-step or multistep hypothesis for malignant transformation, the prolonged preleukemic course in patients with -7 as the only abnormality could represent a premalignant stage, in which further evolution is required for development of overt leukemia. The patients showed a random distribution of blood groups and HLA types.