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hronic myeloid leukemia (CML) is a clonal bone marrow disease characterized by the presence of the Philadelphia chromosome, resulting from translocation between chromosomes 9 and 22 producing the BCR-ABL hybrid gene., which encodes tyrosine kinase proteins and regulate cell growth. The development of targeted therapies for the treatment of this disease, such as imatinib mesylate, changed the landscape treatment of CML. Hematopoietic stem cells transplantation (HSCT) still remains the only curative modality of therapy. After HSCT, relapse can be observed even very late. The amount of leukemic cells in relapse (molecular, cytogenetic or hematologic) and relapse phase are the main prognostic factors found, and the response to the interventions (infusion of donor lymphocytes or imatinib mesylate) are best when relapse is identified early. The use of real-time PCR for the detection of BCR-ABL gene for monitoring of recurrence in patients after HSCT shows a good alternative of tracking disease, however cut-offs which would define relapse are not yet established in the literature. Besides, there have been recent changes in the PCR methodology including the padronization of an international scale, used as monitorization for TKI therapy. Few studies evaluated this method for monitoring patients after HSCT.

The main objective of this study is assessing the significance of the results of real-time PCR for quantification of BCR-ABL gene in patients previously diagnosed with CML who underwent HSCT. The intention is to analyze if the results of this test are reliable predictors of the risk of disease recurrence and what is the range of values that is considered at increased risk for relapse, which would allow early intervention.

We retrieved databases and records of 57 patients diagnosed with CML who were treated with HSCT from 2003 in the HC-UFPR. Type of relapse (hematology or cytogenetic ) and correlation with BCR-ABL values obtained by real-time PCR, is the primary endpoint.

We identified 57 patients which received HSCT from 2003-2014. All them had been molecularly monitored by Real Time Q-PCR and have more than one value measured. 21 patients had positive Q-PCR results. From those, 17 had persistent positive results, and 12 of them ultimately relapsed. Four patients had intermitent low values of BCR-ABL and so far no one of them relapsed. No patient with persistent negative brc-abl relapsed. IS ratio of patients who relapsed were significantly higher than those who didn't relapse, which had IS showing 2-3 log reduction. Patients with intermitent low values of BCR-ABL had IS showing 3 log reduction altenating with negative results.

Although there were changes in BRC-ABL techniques, real time Q PCR can be used for monitorization of relapse after transplant. Persistent positive results highly correlated with relapse within the present cohort of patients. However, low levels aternated with negative results did not resulted in a higher rate of relapse. Patients with persistent negative measuses did not relapse at all.