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BCR-ABL Kinase Domain Mutations/ABL Sequencing (Qualitative)

Test Code: 4020 Department: Hematological Malignancies
Test Synonyms: Imatinib resistance mutation testing Tyrosine kinase inhibitor resistance mutation testing; ABL mutation testing for chronic myeloid leukemia
CPT Code(s): 81403

Background:
Tyrosine kinase inhibitors such as imatinib mesylate are the mainstay of targeted therapy for chronic myeloid leukemia.  Tyrosine kinase inhibitors act by blocking the ATP binding site of BCR-ABL kinase, the abnormally active enzyme responsible for uncontrolled myeloproliferation in chronic myeloid leukemia.  However, a mutation in ABL kinase’s ATP binding site or in another domain may abrogate the potency of imatinib and newer generation tyrosine kinase inhibitors to control chronic myeloid leukemia.  Hence, ABL kinase domain mutation analysis is indicated in patients who failed or are at risk of failing imatinib or other tyrosine kinase inhibitor therapy.  

Clinical Utility:
In patients who failed or are at risk of failing tyrosine kinase inhibitor therapy, knowledge of the mutation type in the ABL kinase domain responsible for resistance is intended to aid clinical assessment and management planning.    

Methodology:
This assay is based on RT-PCR amplification of the entire ABL1 kinase domain followed by direct DNA sequencing by the Sanger method.  Sequencing will detect all known mutations associated with drug resistance.  

Sensitivity: 
Assay sensitivity is at ~20% mutant clone’s abundance in the back-ground of wild-type clones.  Note: PCR-based DNA sequencing will likely not be technically feasible if the BCR-ABL1 RNA level is more than ~2.5 logs below the baseline.   Results are reported as “positive” or “undetected.”

Specimen Requirements:

  • A 10-20 mL sample of blood or bone marrow in a yellow (ACD) or purple (EDTA) tube (mixed thoroughly). 
  • Deliver to lab at shipping address above within 24 hours of collection, if sample cannot arrive within 24 hours, refrigerate until sample can be transported, then transport on ice packs; do not freeze.
  • If sample is to be shipped overnight, pour blood/bone marrow into RPMI media at a 1:1 ratio (1 mL of RPMI to 1 mL of blood/bone marrow) and mix thoroughly.
  • If our lab is used to monitor the patient’s BCR-ABL1 RNA levels (by RQ-PCR), the same sample that was used for quantitative PCR can also be used for sequencing.  We routinely store these samples (stabilized) for several weeks after RQ-PCR reporting.  Please call Client Services at (855) 535-1522 to order sequencing.  

A REQUISITION FORM MUST ACCOMPANY ALL SAMPLES. Please include detailed clinical information.

Test Performed (Days):
Weekly

Turn Around Time:
7-10 days

Shipment Sensitivity Requirements:
Keep specimen cold during transit, but do not ship on dry ice.  Please contact Client Services at (855) 535-1522 for shipping kits and instructions.  Use the cold pack provided in the KDL shipping kit.  Ship the specimen overnight express, using the FedEx priority overnight label provided.  The specimen must arrive at the lab no more than 24 hours after collection.

References:

  1. Jabbour E. Branford S. Saglio G. et al. Practical advice for determining the role of BCR-ABL mutations in guiding tyrosine kinase inhibitor therapy in patients with chronic myeloid leukemia. Cancer 2011; 117:1800-11.
  2. Hughes T. Saglio G. Branford S. et al. Impact of baseline BCR-ABL mutations on response to nilotinib in patients with chronic myeloid leukemia in chronic phase. Journal of Clinical Oncology 2009; 27:4204-4210.

Additional Info: