Molecular Status Evaluation in a Standardized Laboratory in a Cohort of Patients with Chronic Myeloid Leukemia At the Instituto Mexicano Del Seguro Social (IMSS)

Molecular Monitoring of BCR-ABL through standardized qPCR according to the international scale (IS) has been recently included in the follow-up of CML patients treated with tyrosine kinase inhibitors (TKIs) at the IMSS. The Molecular Biology Laboratory of the “Hospital of Specialties” at the “National Medical Center Siglo XXI”, have recently achieved full standardization of the qPCR technique to the international scale (using a conversion factor provided by Adelaide lab). The use of the IS in the molecular monitoring expressed as Bcr-Abl/Abl ratio in percentage is very important, since this is the best way to adopt appropriate strategies with TKI therapy.

To report the evaluation of molecular status of 485 patients with CML attended at the Instituto Mexicano del Seguro Social using the IS in a reference standardized Mexican laboratory.

From August 2011 to May 2012, peripheral blood samples of 485 patients with CML, were sent to our laboratory. We extracted RNA as previously described. A minimum of 5 ml of whole blood was required in order to maximize optimal results. Then we put these results in our database and classified patient samples in five groups according the percentage of Bcr-Abl/Abl in the international scale: The first group were patients with >10% of Bcr-Abl; the second group were patients with >1–10% of Bcr-Abl; the third group were patients with >0.1–1%; the fourth group were patients with ≤0.1% and the fifth group were patients with undetectable Bcr-Abl transcripts.

We found the following distribution: Group I (> 10% Bcr-Abl): 91 patients (18.76%); Group II (>1–10% Bcr-Abl): 65 patients (13.4%); Group III (>0.1–1% Bcr-Abl) 83 patients (17.11%); Group IV (≤0.1% Bcr-Abl) 122 patients (25.15%); and Group V: undetectable Bcr-Abl: 124 patients (25.56%).

Fifty percent of CML patients treated with nilotinib, imatinib or dasatinib, have reached a deep molecular response, that is, Major Molecular response (MMR) or better. Another 17% has reached a molecular response (>0.1–1%) that is equivalent to Complete Cytogenetic response (CCyR). This information is very useful for clinicians and should be interpreted individually according the lenght of treatment with TKIs, following current CML guidelines and recommendations. Until now, molecular monitoring using the IS was only possible through sending samples to US laboratories. It is important that Mexican clinicians at our institution have now the opportunity to rely on a Mexican validated and standardized laboratory. The results of the molecular response in this cohort of CML patients can be compared to the data of another countries using the IS. Classifying patients according to their molecular status could help to optimized therapies at our institution.

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