Characterization of Real World Treatment Patterns and Outcomes Among Older Adults with Chronic Lymphocytic Leukemia in the Pre Novel-Agents Era: An Analysis of the 2007-2013 SEER-Medicare Database

Background: Chronic lymphocytic leukemia (CLL) is the most common leukemia among adults in Western countries with a median age of 72 years at diagnosis. Data from recent randomized clinical trials of novel agents, such as ibrutinib, have shown significant improvements in overall survival (OS) among older CLL patients. Prior to the introduction of kinase inhibitor therapies, chemoimmunotherapy combinations were the mainstay treatment. However, older individuals and/or those with co-morbid conditions may be less likely to tolerate standard CLL chemoimmunotherapy. While we await real-world outcomes data on how novel agents have continued to change the CLL landscape, little is known about the management and survival among older CLL patients prior to the availability of novel agents in clinical practice. Our study uses comprehensive prescription and medical insurance claims linked with registry data to describe the time to treatment initiation, front line therapy, and survival outcomes in older adults with CLL between 2007-2013--an era that predates the approvals of ibrutinib, idelalisib and obinutuzumab.

Methods: The study used the 2007 to 2013 SEER-Medicare linked database. The sample included patients with first primary tumor site as CLL or SLL (ICD-O histology codes 9670 and 9823) diagnosed between 2007 and 2011. This date of first diagnosis of CLL or SLL defines the index date. Patients aged > 65 years with Medicare fee-for-service coverage in the 12 months pre-index and Medicare fee-for-service and prescription drug coverage in the 6-months post-index period or until death were included. Study outcomes included time to first treatment since CLL/SLL diagnosis, type of treatment initiated, and OS since first treatment. The first treatment type was classified into 6 groups (rituximab monotherapy, chlorambucil monotherapy, rituximab + bendamustine, rituximab + fludarabine +/- other treatment, rituximab + other chemotherapy, and other chemotherapy without rituximab). Logistic regression examined factors associated with receiving any treatment within 1- and 2-years of diagnosis. Cox regression examined factors associated with OS. Covariates in both sets of models included age, gender, race, region, low-income subsidy status, anemia/thrombocytopenia at diagnosis, comorbidities, disability status, and year of diagnosis. Cox regressions also included covariates for time to treatment and type of first treatment.

Results: We identified 3,214 newly diagnosed CLL/SLL patients. Our sample had a mean age of 78 years (SD: 8), 49% were male, and 30% had anemia and/or thrombocytopenia at diagnosis. Nearly 33% of the patients received at least one CLL treatment over a median follow-up of 1,099 days (IQR: 834-1735 days) from the date of diagnosis. The most common treatments were rituximab monotherapy (26%), fludarabine + rituximab +/- other treatment (23%), and chlorambucil monotherapy (16%). Among those who initiated treatment, the median time to initiation was 791 days (IQR: 127-1344 days) from diagnosis. Logistic regressions indicated that patients aged 75-79 years old (vs. 80+ year olds) and those with anemia and/or thrombocytopenia at diagnosis were significantly more likely to initiate treatment within 1- and 2-years of diagnosis.

The median OS from treatment initiation among the 1,047 treated patients was 52.4 months (Figure 1). The estimated 1-year and 2-year OS since treatment initiation was 81% and 69%, respectively. The OS at 2 years was 68% for rituximab monotherapy, 73% for fludarabine + rituximab +/- other treatment, and 59% for chlorambucil monotherapy. Cox regressions showed older age, male gender, disability, higher comorbidity scores, and type of first treatment (chlorambucil monotherapy vs. rituximab as monotherapy or in combination with chemotherapies) to be significantly associated with lower OS.

Discussion: About one-third of older individuals who were newly diagnosed with CLL initiated treatment over a median follow-up of 3 years. This real world study shows modest 2-year OS in older CLL patients after initiating treatment in the pre-novel therapy era. While available clinical trials suggest novel CLL agents offer significant improvements in survival for older adults with CLL, future studies should examine CLL outcomes in real world settings to correlate how results obtained in recent landmark clinical trials translate into clinical practice.

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