Validation of Kantarjian (2010) Model for Intensive Chemotherapy in Older Adults with Acute Myeloid Leukemia
Authors: Tahata Shawn , Im Annie , Boyiadzis Michael , Normolle Daniel 
Published: October 2019

Abstract
Background: Acute myeloid leukemia (AML) carries a poor prognosis in older adults. Limited clinical trial data exist to support the use of conventional cytarabine-based regimens in this population, and practice standards have been extrapolated from studies in younger patients. Intensive chemotherapy in older adults is associated with high rates of treatment-related mortality and poor overall survival. In 2010, Kantarjian and colleagues developed a risk model for 8-week mortality using adverse prognostic risk factors, including age ≥80 years, complex karyotype (≥3 abnormalities), poor performance status (ECOG score ≥2), and serum creatinine >1.3 mg/dL. This study validates the Kantarjian model for progression-free survival (PFS) and overall survival (OS) in older patients with AML treated with intensive chemotherapy.
Methods: Adults aged ≥70 years with AML (≥20% blasts in bone marrow or peripheral blood) who received intensive chemotherapy at UPMC Hillman Cancer Center between 2000 and 2011 were evaluated. Patients were stratified into low, intermediate, and high-risk groups according to the Kantarjian (2010) model and analyzed for PFS and OS using the Kaplan-Meier method. Differences in PFS and OS between risk groups were assessed with the log-rank test. ECOG performance status was estimated using historical data at the time of diagnosis. Additional variables, including AML type (primary vs. secondary), percent blasts at diagnosis, percent CD34-positive blasts, hemoglobin, leukocytes, platelets, LDH, AST, ALT, total bilirubin, albumin, and Charlson comorbidity index (CCI) were tested for added prognostic value when incorporated into the model, using Cox proportional-hazards regression for PFS and OS.
Results: Clinical data were collected for 68 patients. Of these, 26 patients, all of whom were diagnosed prior to 2003, were excluded from the final analysis due to insufficient electronic health records. The remaining 42 patients were used for the validation study. Median age at diagnosis was 73 years (range: 70-87). Twenty-seven patients (64%) had primary AML, whereas 10 (24%) had AML evolving from another hematologic disorder and 5 (12%) developed AML after radiation or chemotherapy for another malignancy. Eleven (26%) patients had ≥3 karyotypic abnormalities and the remaining 31 (74%) had fewer than 3. Thirty-three (79%) patients had an ECOG performance status of 0 or 1, and the remaining 9 (21%) did not have sufficient historical data to estimate ECOG score and were given a score of 0. In total, there were 23, 16, and 3 patients categorized into the low, intermediate, and high-risk groups, respectively. These groups had non-overlapping PFS and OS curves (p <0.001 for both endpoints). The low, intermediate, and high-risk groups had median PFS of 9.6, 5.1, and 2.1 months and median OS of 14.0, 6.3, and 2.1 months, respectively. None of the additional variables were found to add significant prognostic value to the existing model.
Discussion: The Kantarjian (2010) model is a valid method of risk-stratifying older adults with respect to PFS and OS, and may be useful when weighing the risks and benefits of intensive chemotherapy in these patients. In this study, we did not identify other disease characteristics or measures of organ function that significantly improved the model, although our analysis is limited by small sample size. We note that all patients in our study had an ECOG score of 0 or 1, implying selection of healthier patients for induction chemotherapy at our institution. Our results suggest that patients in the intermediate and high-risk groups may not derive significant PFS and OS benefit from intensive chemotherapy when the risks of morbidity and mortality from treatment are considered.

Disclosures
No relevant conflicts of interest to declare.