Abstract # 3846 – Landmark Response and Survival Analyses from 206 AML Patients Treated with Guadecitabine in a Phase 2 Study Demonstrate the Importance of Adequate Treatment Duration to Maximize Response and Survival Benefit. Survival Benefit Not Restricted to Patients with Objective Response
Authors: Karen W.L. Yee, MD1, Gail J. Roboz, MD2, Casey L. O’Connell, MD3, Elizabeth A. Griffiths, MD4, Raoul Tibes, MD, PhD5*, Katherine J. Walsh, MD6, Wendy Stock, MD7, Guillermo Garcia-Manero, MD8, Michael R. Savona, MD9, Farhad Ravandi, MD10, Naval G. Daver, MD11, Elias Jabbour, MD8, Todd L. Rosenblat, MD, MS12*, Jean-Pierre Issa, MD13*, Xiang Yao Su, PhD14*, Mohammad Azab, MD14 and Hagop M. Kantarjian, MD8
1Leukemia Program, Department of Medical Oncology and Hematology, Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada; 2Weill Cornell/NY Presbyterian Medical Center, New York, NY; 3Keck School of Medicine, University of Southern California, Los Angeles, CA; 4Roswell Park Cancer Institute, Buffalo, NY; 5Mayo Clinic Arizona, Scottsdale, AZ; 6The Ohio State University, Columbus, OH; 7University of Chicago Medical Center, Chicago, IL; 8The University of Texas MD Anderson Cancer Center, Houston, TX; 9Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN; 10Department of Leukemia, The University of Texas MD Anderson Cancer Center, Houston, TX; 11University of Texas MD Anderson Cancer Center, Department of Leukemia, Houston, TX; 12New York-Presbyterian/Columbia University Medical Center, New York, NY; 13Fels Institute, Temple University, Philadelphia, PA; 14Astex Pharmaceuticals, Inc., Pleasanton, CA
Background: Guadecitabine is a next generation subcutaneous (SC) hypomethylating agent (HMA) resistant to degradation by cytidine deaminase which results in prolonged in vivo exposure to the active metabolite decitabine. We conducted a phase 2 study of guadecitabine in 206 AML patients. International guidelines recommend a minimum of 4 to 6 cycles of HMA treatment to gain maximum benefit, but some suggest that treatment may not be beneficial if no response was observed after 4 cycles. No prospective studies have confirmed the correlation between an HMA number of cycles with response and survival using landmark methodology. We present here the results of landmark response and survival analyses based on number of cycles and whether patients had an objective response or not.
Methods: Landmark response (CR, CRi, or CRp based on 2003 IWG criteria, grouped together as composite CR or CRc), and overall survival (OS) analyses for patients alive at or beyond month 3 and month 5 (time of planned start of cycle 4 and cycle 6 respectively) were conducted. Landmark OS was compared between patients who received at least 4 or 6 cycles and those who did not. The landmark methodology avoids the bias of early deaths before cycles 4 and 6 attributing a survival benefit in those who did not die early and were able to get more cycles. We also compared the result in responding and non-responding patients to see if survival benefit was restricted to responding patients only.
Results: The study completed enrolment with 206 AML patients: 103 patients (50%) for each of Treatment Naïve (TN) unfit for intensive chemotherapy, and relapsed/refractory (r/r) AML. Median age was 68.5y (range 22-92y), ECOG PS ≥2 in 26%, poor risk cytogenetics in 41%, secondary AML in 26%, and median baseline BM blasts % was 40% in the total AML population. 108 patients (52.4%), and 155 patients (75%) received <4 and <6 cycles respectively. The primary reasons for treatment discontinuation before 4 and 6 cycles respectively (% from the total population of 206 patients) were early progression (20.4, and 30.6%), and early death (12.6%, and 17%). However, 9.7% and 14% discontinued treatment before 4 or 6 cycles respectively as a result other less objective reasons such as patient decision, investigator decision, or adverse events which might have been manageable without treatment discontinuation. The landmark analysis population included 161 patients for 4-cycle analysis, and 133 for the 6-cycle analysis. In those patients, there were no major differences in baseline characteristics between those who received at least 4 or 6 cycles and those who did not. In the landmark analysis comparing those who received at least 4 cycles (97 patients) and those who did not (64 patients), CRc rate was 62% vs 25% (p < 0.0001) and median OS was 13.7 m vs 6.1 respectively (HR 0.53, 95% CI 0.37-0.75, p 0.0003). In the landmark analysis comparing those who received at least 6 cycles (51 patients) and those who did not (82 patients) the CRc rate was 82.4% vs 35.4% (p < 0.0001), and median OS of 19.9 m vs 8.8 m respectively (HR 0.42, 95% CI 0.27-0.64, p <0.0001). The results were consistent when TN and r/r AML patients were analyzed separately. More interestingly the landmark OS benefit in patients who received at least 4 or 6 cycles was also evident in patients who did not have an objective CRc. Patients with no CRc who received at least 4 cycles had a median OS of 8 m vs 5.4 m in those who did not (HR 0.63, 95% CI 0.40-0.98, p 0.04). Patients with no CRc who received at least 6 cycles had a median OS of 12.9 vs 8 m in those who did not (HR 0.40, 95% CI 0.17-0.94, p 0.03).
Summary/Conclusions: In a prospective phase 2 study of 206 TN and r/r AML patients treated with the HMA guadecitabine, patients who were alive at or beyond 3 and 5 months who continued treatment for at least 4 or 6 cycles respectively achieved a highly significant response and survival benefit compared to those who discontinued treatment before cycle 4 or 6. The survival benefit was evident even in patients who did not have an objective response. Reasons for treatment discontinuation should be weighed carefully before stopping HMA treatment with guadecitabine before 4 or 6 cycles in AML patients to maximize response and survival benefit. Failure to achieve an objective response after 4 cycles should not be a reason for treatment discontinuation as long as patient can still benefit.