Patient Characteristics and Treatment Patterns in Elderly Adults with Relapsed or Refractory Acute Lymphoblastic Leukemia Using 100% Medicare ALL Data

Introduction: Acute lymphoblastic leukemia (ALL) is a very rare disease with a poor prognosis in elderly (>65 years) adult patients. Prognosis is worse in patients who have relapsed or refractory ALL (R/R ALL). Because there is limited real-world data on elderly patients with R/R ALL, we aimed to describe patient characteristics and treatment patterns among these patients in a large population-based dataset.

Methods: Using 100% Medicare ALL administrative claims data from 2007-2012, we identified patients aged ≥ 66 years who were newly diagnosed with ALL in 2008-2011, continuously enrolled in Medicare fee-for-service (FFS) for 12 months prior to ALL diagnosis date, and continuously enrolled with Medicare Part D coverage for at least 30 days after diagnosis. Presence of ALL was defined as ≥1 Part A inpatient (IP)/skilled nursing facility (SNF)/home health agency (HHA)/hospice (HS) claim or ≥2 Part A outpatient (OP)/Part B (PB) claims occurring on different dates in any 2-month interval with an ICD-9 diagnosis code for ALL; date of ALL diagnosis was defined as the earlier date of the 1^st IP/SNF/HHA/HS claim or the 2^nd of 2 OP/PB claims carrying an ALL code. Follow-up for R/R disease began after the ALL diagnosis date, and was limited to a cohort of patients who had also received chemotherapy or a tyrosine kinase inhibitor (TKI) within 90 days of the ALL diagnosis date. Patients were identified as having R/R ALL if they had one of the following criteria: 1) a claim with an ICD-9 diagnosis code for R/R ALL (204.02) in any position after treatment was initiated; 2) use of clofarabine, nelarabine or the start of a second chemotherapy course; or 3) a change in type of TKI identified from Part D prescription drug claims. The date of R/R ALL diagnosis was defined as the earliest of date a patient met any of the R/R ALL criteria. Patient characteristics and treatment patterns were described for patients identified as having R/R ALL.

Results: Of the 303 patients who were identified as having ALL from 2008-2011 and had treatment with chemotherapy or TKI within 90 days of the ALL diagnosis date, 144 patients (48%) were identified as subsequently having R/R disease. Of those, 39 (27%) were identified through diagnosis code only, 40% were identified through treatment changes only, and 47 (32%) were identified through both diagnosis codes and treatment changes. The median time from the ALL diagnosis date to date of R/R disease was 201 days, 172.5 days, and 240 days for patients identified using diagnosis codes, treatment changes, and both diagnosis codes and treatment changes, respectively. Overall, 81 (56%) patients with R/R ALL defined at the changes in treatment with or without a subsequent diagnosis.

Patients who were identified with R/R ALL were slightly younger and had fewer comorbidities than the overall group of patients diagnosed with ALL (Table). Of the patients identified with R/R ALL, 126 (88%) were treated with any chemotherapy or TKIs; 120 (83%) patients were treated with chemotherapy and 26 (18%) patients were treated with TKIs. Eleven (8%) patients received a bone marrow/stem cell transplant. Of the 120 patients treated with chemotherapy, 73% had only one chemotherapy course and 51% had the first chemotherapy administration in an outpatient setting. Vincristine alone or in combination with other agents was the most commonly observed type of chemotherapy. Of the 26 patients who were treated with TKIs, 42% had only one course and 69% were treated with dasatinib.

Conclusions: These data describe real-world patient characteristics and treatment patterns in elderly patients with R/R ALL. Approximately half of the elderly ALL patients who were treated for ALL within 90 days of diagnosis were identified as having R/R ALL through administrative claims data, and more than half were identified through changes in treatment and not through the use of diagnosis codes. Thus, we are likely underestimating the true proportion of elderly ALL patients who have R/R disease. Interestingly, we observed that 51% of patients treated with chemotherapy had the first chemotherapy administration in an outpatient setting, and that only 8% of patients received a bone marrow/stem cell transplant.

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