(P-028) Survival in Older Adults Treated for Chronic Lymphocytic Leukemia Compared to Those Without Cancer: An Exploratory Time-trend Analysis

Background: While prognosis for patients with CLL has improved over the past decade, data suggest that benefits have largely accrued in younger adults, with modest benefits observed in older adults. These studies were conducted prior to approvals of new therapies that are well-tolerated in older adults.

Objectives: The objective of this study was to describe three-year survival in older adults diagnosed with CLL and compare it with survival in similar older adults without cancer, by year of treatment initiation.

Methods: We used Surveillance, Epidemiology, and End Results (SEER)-Medicare data to identify older adults (≥66 years) diagnosed with primary CLL between 2004 and 2015 who initiated CLL-directed therapy within one year of diagnosis. For inclusion, patients needed continuous Medicare Parts A/B and no managed care coverage in the year prior to treatment initiation (index date); those initiating from 2007 also needed continuous Part D coverage. CLL patients were matched in a ratio of 1:5 to Medicare beneficiaries without cancer based on birth year, sex, and region. Non-cancer comparators were assigned the index date of their matched CLL patient and had to meet the same coverage requirements. Individuals were followed from index date until death, end of eligibility, or end of study (December 31, 2016). For each year from 2004-2012, three-year survival for CLL and non-cancer cohorts was estimated using Kaplan-Meier methods. Inverse probability weighted Cox regression models were used to compare survival in CLL and non-cancer cohorts, accounting for demographics and comorbidity and frailty indices, and were further stratified by time (pre-2010 vs. 2010 onwards).

Results: The CLL cohort included 1,807 patients. Mean age was 77 years and 43% were female. Three-year survival ranged from 56% (95% CI 49-63%) in 2004 to 63% (95% CI 53-71%) in 2012 in the CLL cohort and 75% (95% CI 72-77%) in 2004 to 64% (95% CI 60-68%) in 2012 in the non-cancer cohort. Mortality HRs comparing the CLL and non-cancer cohorts stratified by time were 1.28 (95% CI 1.18-1.39) in the earlier and 1.04 (95% CI 0.93-1.17) in the later period. Patient comorbidity and frailty indices among the non-cancer cohort were greater in years ≥ 2010 than <2010, however, sensitivity analyzes standardizing to the comorbidity distribution in 2015 produced similar results.

Conclusions: Survival in older adults treated for CLL improved over time, approaching survival observed in similar older adults without cancer after 2010. This exploratory analysis suggests these improvements may be in part due to the introduction of more tolerable and efficacious CLL treatment options for older adults.