Epigenetic Priming Using Decitabine Followed By Cytarabine As an Induction Regimen in Older Patients with Newly Diagnosed Acute Myeloid Leukemia

Background:

Acute myeloid leukemia (AML) in older patients is associated with a poor prognosis, with lower complete remission (CR) rates and worse overall survival compared to younger patients. Moreover, most older patients over the age of 70 years do not tolerate standard induction chemotherapy. Alternative therapy with hypomethylating agents can improve CR rates and survival compared to best supportive care, but overall outcomes remain poor after current therapeutic options in this patient population. Preclinical studies suggest that “epigenetic priming” using decitabine followed by cytarabine increases the cytotoxicity of cytarabine. It is hypothesized that this is due to the reactivation of genes that have been silenced by the malignancy. The aim of this phase II study is to evaluate the efficacy and safety of a novel induction regimen using decitabine followed by cytarabine in older patients with newly diagnosed AML who are not candidates for intensive chemotherapy. Here we present response rates and treatment-related mortality for the first 23 evaluable subjects.

Methods:

A phase II, single arm study of decitabine and cytarabine is ongoing at the University of Pittsburgh Cancer Institute (NCT 01829503) for patients over the age of 70 years with newly diagnosed AML, or patients over the age of 60 years who are considered not to be candidates for intensive chemotherapy. The induction regimen consists of decitabine 20mg/m² intravenously (IV) x 5 days followed by standard dose cytarabine 100mg/m² continuous IV infusion x 5 days. Patients with no evidence of disease on day 15 bone marrow biopsy proceed with maintenance decitabine. Patients with persistent disease but no evidence of progression proceed with a second cycle of induction using the same regimen. Patients with progressive disease after 1 cycle are taken off study. After a second induction cycle, patients with no evidence of disease, or persistent disease but no evidence of progression, proceed with maintenance decitabine. Maintenance cycles consist of decitabine 20mg/m² IV x 5 days every 4-8 weeks until disease progression. Response rates are evaluated by the International Working Group Response Criteria in AML. Treatment-related mortality is defined at mortality within 8 weeks of initiation of induction therapy.

Results:

Twenty-five subjects of a planned 37 subjects have been enrolled as of August 2014, 23 of whom were evaluable for response at the time of analysis. At the time of this preliminary analysis, the median age was 76 years (range 68-82 years). There are 11 females (44%) and 14 males (56%). The median ECOG performance status was 1 (range 0-2). There were 14 patients with poor risk cytogenetics at diagnosis. Of the 23 patients who are evaluable for response, there were 14 (61%) patients with a CR and 2 patients with a CRi (CR+CRi rate 70%). Two patients had a partial remission, 1 patient had a morphologic leukemia free state, and 4 patients had resistant disease. All patients except for 2 received 2 cycles of induction. Of the 14 patients who had poor risk cytogenetics at diagnosis, 10 (71%) had a CR, and 8 had normalization of their previous cytogenetic abnormalities. There have been no treatment-related mortalities to date.

Conclusion:

We have shown that an induction regimen using decitabine as an epigenetic primer followed by cytarabine induces high CR+CRi rates with no treatment-related mortality in older adults with newly diagnosed AML who are not candidates for intensive chemotherapy, a patient population in whom there exists a dire need for novel treatment strategies. In the first report of this phase II study, 70% of patients achieved a CR or CRi, and there were no treatment related mortalities. This compares favorably with historical outcomes of both intensive chemotherapy and decitabine monotherapy in older adults in terms of safety and efficacy, respectively. Final analysis of this clinical trial will include overall survival analysis, rate of grade III and IV adverse events, and epigenetic correlative studies. We have demonstrated that decitabine followed by cytarabine is a safe and effective regimen in older adults with newly diagnosed AML.