ASO-PCR based detection, clinical significance and prevalence of T315I mutation in Indian chronic myeloid leukemia patients treated with Imatinib mesylate: First study from India

B26

BACKGROUND 
 Imatinib mesylate has become the frontline therapy in all stages of Chronic Myeloid Leukemia patients but the development of resistance in 10% to 15% cases is the main cause of its failure. In 80% to 90% of relapsed cases ABL kinasedomain mutations have been detected. Early detection of T315I mutations may allow timely treatment intervention to prevent disease progression or overcome resistance in CML patients.
 LACUNAE: 
 
 Clinical significance and prevalence of T315I mutation in Indian CML patients treated with Imatinib mesylate. 
 
 AIMS 
 Ø To detect T315I mutation in chronic myeloid leukemia patients treated with imatinib mesylate by Allele specific-oligonucleotide- PCR. 
 Ø To study prevalence of T315I mutation in relapsed CML patients . 
 
 
 METHOODOLOGY: 
 All Chronic Myeloid Leukemia patients at presentation were diagnosed by RT-PCR at Leukemia Research Lab ,Haematology department ,AIIMS. .Imatinib (400mg/day) was used as the frontline therapy in all cases of CML. All 200 CML patients were screened for T315I mutation by Allele specific-oligonucleotide-PCR (ASO-PCR). The patients were evaluated for hematologic and molecular responses, time to progression, survival and toxicity. 
 RESULTS: 
 
 The study included 200 newly diagnosed CML patients .A fraction of CML patients treated with Imatinib developed hematological and molecular resistance i.e., 45/200 and. The ten CML cases (10/200) were in AP/BC CML at presentation . All 200 CML patients were screened for T315 mutation by ASO-PCR. The 37/45/200 (Who developed Haematological and Molecular relapse) were positive for T315I mutation . The 8/10 cases who were in advanced stage were positive for T315I mutation .The T315I positive cases showed poor prognosis and rapid progression to advanced disease . T315I mutation was found to be the main cause of Imatinib failure in our CML patients .It was detected in 80% to 85% of our relapsed cases . Survival and time-to-progression curves were obtained from Kaplan-Meier method. Toxicity : The anemia was induced in 30 cases ,thrombocytopenia in 40 and hypo pigmentation in 20 cases .The progression to AP/BC-CML was seen in 20 cases. 
 Noted : 
 The overall prevalence of T315I mutations in our relapsed CML patients was 20 to 25% after a follow up of more than 3 years. Finally 10 imatinib resistant CML patients were treated with dasatinib at 70mg/day . 
 
 Clinical Significance of study 
 
 India is a developing country; the CML patients cannot effort expensive tests like sequencing for BCR-ABL mutation. So we had standardized ASO-PCR for routine screening of T315I mutations which was economical ,sensitive and rapid . 
 
 Conclusion 
 Ø The early detection by ASO-PCR assay proved to be helpful in clinical management of therapeutic decisions in CML patients. 
 Ø 
 ASO-PCR proved to be very economical, sensitive and rapid technique for detection of known ABL mutations like T315I s and is even sensitive than mutation detection by sequencing . 
 Ø 
 The detection of T315I mutation using a ASO-PCRtechnique was almost always associated with imatinib resistance and patients had poor prognosis. 
 Ø 
 T315I has turned out to be a multityrosine kinase inhibitor resistant mutations in CML patients treated with imatinib ,dasatinib and Nilotinib .