Phase 2 Study of 5 Days Azacytidine Priming Prior to Fludarabine, Cytarabine and G-CSF Combination for Patients with Relapsed or Refractory AML

Background: Acute Myeloid Leukemia (AML) is a group of heterogeneous clonal disorder of myeloid progenitor cells. Relapsed and refractory AML represent a clinical and therapeutic challenge to hematologist because of chemotherapy resistant disease and are associated with poor outcome. Allo-SCT is the only potentially curative therapy for such patients and is only possible after achieving second remission. FLAG is used more commonly and is associated with around 50%. We hypothesize that pretreatment with azacytidine will improve the overall response rate and remission status.

Objectives: The primary objective of this study is to evaluate the overall response rate (ORR) of pretreatment with azacytidine followed by FLAG for the treatment of relapsed/refractory AML.

Methods: This is prospective phase II study of patients with diagnosis of refractory/relapse AML at King Fahad Medical City, Riyadh, Saudi Arabia between January 2015 and July 2018. Patient confirmed to be relapse/refractory AML based on bone marrow biopsy results were included. Eligible patients received pretreatment with azacytidine for 5 days (days -5 to -1). The FLAG protocol was started on the next day after the completion of 5-azacytidine. G-CSF was started on day 0 (24 hours after last 5-azacytine dose) and continued for a total of seven days (days 0 to 6). Fludarabine and cytarabine was started on next day after G-CSF start day and continued daily for 5 days (days 1 to 5). Patients were followed up with daily clinical examination and labs until next bone marrow examination at count recovery up to day 35. The bone marrow sample was analyzed for cell cycle and global DNA methylation status before and after azacytidine treatment. The ORR is the proportion of the treated patients who achieved CR or Cri. The toxicity was graded base on the frequency of Adverse Events (the NCI-CTCAE version 4.0 scoring system).

Results:

Sixteen refractory/relapsed AML patients (5 females; 11 males) admitted to our Center from January 2105 to July 2018 were included in the study. Twelve patients were evaluable after exclusion of three patients from analysis based on exclusion criteria. One patient died during induction. The mean age was 39.38 ± 15.11 years. The mean WBC, hemoglobin, platelets, peripheral blood blasts, bone marrow blasts were 26.44 ± 23.15, 7.43 ± 1.55, 61.81 ± 85.20, 49 ± 30.36, and 57.36 ± 29.23 respectively at diagnosis. The mean bone marrow blasts were 42.09 ± 29.75 at relapse/refractory disease.

Seven patient had normal Cytogentics. One patient had BCR (9q43), PML (15q22), RUNX1T1(8q22) & MLL (11q23) genes. Another one had EGR1 (5q31) deletion, while t(8;21) was found in another patient. One patient was positive for 7q31 deletion. Four out of twelve patients had abnormal molecular cytogentics including FLT3 -ITD, CEBPA, FLT3 -TKD mutation and KITD816V. No patient has extramedullary disease at diagnosis or relapse settings.

Seven out of twelve patients had primary refractory disease while five patients had relapsed disease with 6 months' median duration of remission (Range 1.25-84). Nine patient received 3+7 induction regimen at diagnosis while three had ICE protocol. Eight out of twelve patients showed complete response (67%). Four out of five relapsed patients achieved complete response (80%) whereas four out of seven (57.14%) achieved complete response in refractory disease. Eight patients were referred for stem cell therapy. The most common toxicity was cytopenia and bacterial infections. One patient has left arm cellulitis whereas one had arthritis with myositis. All patients were successfully treated with antibiotics, one patient died during study period because of severe invasive fungal infection.

Conclusion

Our phase II study preliminary results indicate that the addition of Azacitidene prior to standard therapy can improve the overall response rate and remission status in relapsed/refractory AML. This may provide an opportunity to responding patients to proceed to curative therapy with stem cell transplant.