Long Term Molecular Response To Triple Therapy With High Doses Imatinib In Patients With Chronic Myeloid Leukemia

Imatinib 400 mg daily is considered the best initial therapy for patients with chronic myeloid leukemia (CML) in the chronic phase (CP). However, only minorities of patients have a complete molecular remission (CMR) Another agent has antileukemic activity against Bcr-Abl-positive cells like Ara-C and interferon, the association of this drugs and imatinib in CML was evaluated in several trials with an increase in molecular response.

The aim of this study was to evaluate the major molecular response (MMR) at 12 months with triple treatment schedule, analyze the evolution of these patients and general and hematologic toxicity.

Patients diagnosed with CML at the Hospital General de Zona #35 in Juarez, Mexico were included. Eligibility criteria were adults with diagnosis of CML chronic phase on triple regimen for at least 12 months: Pegylated interferon-α 2a 90mcgrs via subcutaneous / week for 4 weeks + PO imatinib 800 mgs a day for 30 days + 20 mgs/mt² cytarabine from day 1 to 10 subcutaneus. Patients were stratified according to Sokal score at diagnosis. The molecular analysis was performed in Quest diagnostic laboratory by means of real-time quantitative polymerase-chain-reaction (RT-PCR) results are expressed as a percent ratio of BCR-ABL1 to ABL1 and further adjusted to the international scale (IS) since august 2012.

Patients could have received previous treatment for CML, with the exception of bone marrow transplantation. All patients provided written informed consent. This study was conducted in accordance with the Declaration of Helsinki.

Molecular and adverse events were assessed. An analysis of molecular response at 12 months was planned and follows up patients with MMR every year. A MMR was defined a Bcr-Abl 0.1% or less and complete molecular response (CMR) as undetectable. Hematological toxicity was assessed according WHO scale.

41 patients completed the first 12 months in therapy, with a mean age of 44.4 years (17 to 71) 51% male and 49% female, the median and ranges of hemoglobin levels, leukocyte and platelet counts at diagnosis were 10.2 g/dl (5.1-16.0), 209.000 μL3 (10,600 - 529.000) and 565.500 μL (130.000 to 4,272,000) respectively. The percentages of cases by Sokal risk group were 70.7% low, 24.4% intermediate and 4.9% high risk.

The Median follow up time was 58 months (range 14 to 120). At 12 months the number of patients who were in MMR was 27 (65.9%) including 8 (19.5%) with no BCR-ABL detectable. Median duration of triple therapy exposure at first year was 24 Weeks (range 12 to 32)

Responses by Sokal score were 62%, 70% and 100% for low, intermediate and high respectively. Adverse events occurred in 88% cases; 33% of patients has at least one adverse event (AE) 42% 2 EA and 28% 3 EA, the most important EA was gastrointestinal. (table 1) 43.9% of patients has Hematological toxicity III-IV

Median follow up time of patients in RMM was 64 months (range16-120) 2 patients were no evaluable. Patients who have RMM at 12 months 50% achieve a CMR at last follow up, 33% continues in RMM and 17% loss molecular response. Patients with CMR 72% have undetectable bcr-abl, 14% have loss molecular response and 14% in MMR

In this group of patients MMR was achieved in a higher proportion of cases at 12 months of treatment which is important in the long-term prognosis. Side effects grade 3 and 4 hematologic and non-hematologic were significant in this series of cases appearing in 44 and 88% respectively, which requires close monitoring of patients. The combination of interferon α2a, cytarabine and high-dose imatinib induces a MMR of 66% at 12 months of treatment, a 28%, 56% and 16% in MMR, CMR and loss molecular response respectively at last follow up.

Clinical files n =36

No relevant conflicts of interest to declare.