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The majority of patients with acute promyelocytic leukemia (APL) possess either a bcr1 or a bcr3 type fusion between PML and RARalpha genes. The junction sequences may possibly be a target for immune response and influence susceptibility to the disease. In this case, HLA class I allele frequencies would be different between bcr1 and bcr3 patients. To test this hypothesis, we typed 102 APL patients for HLA-A, -B and -Cw alleles. The A*1, A*30, B*51, B*41, Cw*0602, and Cw*1701 alleles showed a different distribution between bcr1 and bcr3 patients, but in no case was this statistically significant after correction for the number of comparisons or was confirmed in an independent panel. Moreover, no difference was detected between bcr1 and bcr3 when HLA alleles were grouped according to their peptide binding specificities. Comparing HLA frequencies, clinical features at diagnosis and clinical outcome of the 64 patients homogeneously treated with all-trans retinoic acid and idarubicin (AIDA protocol) we observed a statistically significant association between HLA-B*13 and risk of relapse by univariate and multivariate regression analysis. Should this finding be confirmed in larger future studies, this observation would be of outmost importance in identifying patients at high risk of relapse in which more aggressive consolidation therapies should be used.

Recent observations of chimerism in patients relapsed following an allotransplant suggest the persistence of immunotolerance, thus offering a biologic rationale for the use of donor lymphocyte transfusion (DLT). In this study, we have analyzed by PCR amplification of several VNTR regions, sequential bone marrow and peripheral blood DNA samples in four patients who received DLT for CML relapse after bone marrow transplantation. Prior to DLT, all patients showed mixed chimerism in peripheral blood cells while two had mixed chimerism and two no chimerism in the BM. None of these four patients showed evidence of chimerism at the cytogenetic level (all had 100% +ve metaphases). After DLT, a complete hematologic and molecular remission (ie disappearance of the BCR/ABL fusion transcript) was obtained in the two patients who had bone marrow mixed chimerism prior to DLT. The two patients without evidence of marrow chimerism prior to DLT converted to a pattern of mixed chimerism after DLT, but both developed a severe bone marrow aplasia occurring at day 56 and 36, respectively. With regard to the sequential analysis of bone marrow chimerism after DLT we observed that: (1) the disappearance of BCR/ABL +ve cells paralleled the conversion to a pattern of full donor chimerism; and (2) the time interval to achieve CR was inversely correlated with the percentage of donor DNA in bone marrow. In conclusion, we have shown here that the assessment of bone marrow pre-DLT chimerism by PCR analysis might predict the response in patients with favorable characteristics, and also might identify patients at high risk of developing severe myelosuppression.

Twenty-five patients (22 adults and 3 infants) with ALL1/AF4-positive acute lymphoblastic leukemia (ALL) were prospectively monitored by reverse transcriptase-polymerase chain reaction (RT-PCR) between January 1992 and July 1999. After high-dose induction and consolidation chemotherapy without bone marrow transplantation, all patients had a complete hematologic remission. Using nested RT-PCR (sensitivity 10(-4)), we observed conversion to PCR negativity in 11 (44%) of the patients. Thirteen of the 14 patients who did not have a molecular remission had a relapse at a median time of 4 months (range, 1 - 20 months). Of the 11 patients who had a conversion to PCR negativity, 5 reconverted to PCR positivity within 1 to 14 months. These 5 patients all progressed to hematologic relapse after 2, 3, 4, 4, and 7 months, respectively. Of the remaining 6 patients, 4 are in persistent hematologic and molecular remission at 12, 14, 88, and 96 months, whereas 2 are early in their follow-up. Actuarial probabilities of relapse and overall survival were 100% and 0% at 14 and 24 months and 67% and 43% at 96 and 100 months, respectively, in patients who had persistent RT-PCR positivity and in those who had a molecular remission. For both relapse and survival, the differences observed between the two groups were significant (P =.003 and P.005, respectively). This study, which represents the first prospective analysis of residual-disease monitoring carried out in a substantial series of patients with t(4;11)-positive ALL, emphasizes the clinical relevance of RT-PCR-based methods to monitor minimal residual disease in this leukemia subset. (Blood. 2000;95:96-101)

In this study we used reverse transcriptase-polymerase chain reaction (RT-PCR) for the longitudinal monitoring of minimal residual disease in 12 patients with All-1/AF-4 positive ALL. Of these, seven also showed at presentation a typical t(4;11) cytogenetic translocation. Seven patients were infants