The importance of cytogenetic studies in adult acute lymphocytic leukemia. PURPOSE: The prognostic importance of pretreatment bone marrow cytogenetic studies in adults with acute lymphocytic leukemia treated at a single institution, with an identical treatment program, is described. PATIENTS AND METHODS: A total of 105 patients with a documented morphologic diagnosis of acute lymphocytic leukemia were reviewed for the purpose of this analysis. All patients had an extensive workup at presentation, and cytogenetic analysis was performed in 103 patients, using the Giemsa banding technique with trypsin pretreatment on 24-hour cultured cells. RESULTS: The specific cytogenetic classification in the 103 patients who had the karyotypic analysis was as follows: diploid 27%; Philadelphia chromosome-positive 13%; hyperdiploid 12%; B-cell karyotype 6%; 6q- and 14q+ abnormalities 4%; pseudodiploid 8%; hypodiploid 2%; and insufficient metaphases 28%. B-cell, 6q- or 14q+, and Philadelphia chromosome-positive karyotypes tended to correlate with other known negative prognostic factors. Patients with diploid, hyperdiploid, pseudodiploid, and hypodiploid karyotypes or with insufficient metaphases could be combined into one group with a favorable prognosis. In this group, the remission rate with induction chemotherapy was 89%, the median complete remission duration was 26 months, and the median survival was 25 months, with a 3-year survival rate of 45%. Patients with Philadelphia chromosome-positive, B-cell, and 6q- or 14q+ abnormalities collectively had an unfavorable prognosis. Their response rate to induction chemotherapy was 65%, the median response duration was 7 months, and the median survival was 8 months, with a 3-year survival rate of less than 10%. CONCLUSION: We conclude that the pretreatment bone marrow karyotype is an important part of the evaluation of adults with acute lymphocytic leukemia and provides significant prognostic information. 