Background: Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) is the most common adult leukemia, accounting for ≈ 37% of all leukemias in the United States. Limited real-word evidence is available on the outcomes of ibrutinib use among previously untreated patients in the U.S. Veterans Health Administration (VHA) population diagnosed with CLL/SLL.

Objectives: To (a) evaluate time to next treatment (TTNT) among U.S. veterans with CLL/SLL who initiated ibrutinib versus chemoimmunotherapy (CIT) in first line (1L) and 1L ibrutinib versus ibrutinib in later lines (2L+) and (b) compare health care resource utilization (HRU) and costs between the 1L ibrutinib and CIT cohorts.

Methods: Adults with CLL/SLL and claims for 1L single-agent ibrutinib or CIT (index date = first prescription claim date) were included from Veterans Health Administration Data (April 1, 2013-March 31, 2018). A subset of the CIT 1L cohort with evidence of ibrutinib in 2L/3L was defined as the ibrutinib 2L+ cohort. Kaplan-Meier curves and Cox proportional hazard models were used to evaluate TTNT, and generalized linear models were used to determine all-cause per patient per month (PPPM) HRU and costs during 1L among propensity score-matched (PSM) cohorts.

Results: After PSM, 614 patients were included in each of the 1L ibrutinib and 1L CIT cohorts, and 149 were included in each of the 1L ibrutinib and 2L+ ibrutinib cohorts. The 1L ibrutinib cohort had significantly longer TTNT compared with each of the 1L CIT and 2L+ ibrutinib cohorts (P <0.0001 and P =0.0001, respectively) and was less likely to have a next line of treatment than the CIT 1L cohort (HR = 0.52; 95% CI = 0.42-0.65; P < 0.0001) and the 2L+ ibrutinib cohort (HR = 0.39; 95% CI = 0.22-0.69; P = 0.0012). The 1L ibrutinib cohort had significantly fewer inpatient visits (rate ratio [RR] = 0.38; 95% CI = 0.28-0.52; P ≤ 0.05) and outpatient visits PPPM (RR =0.72; 95% CI = 0.68-0.77; P ≤ 0.5) compared with the CIT 1L cohort. Additionally, the 1L ibrutinib cohort had $7,308 significantly lower monthly medical costs (95% CI = -$9,892 to -$4,895; P ≤ 0.05) versus the 1L CIT cohort, resulting in comparable monthly total health care cost (medical and pharmacy) between real-world 1L patients treated by ibrutinib and CIT (-$2,160; 95% CI = -$4,840-$347; P > 0.05).

Conclusions: These findings demonstrate that among U.S. veterans with CLL/SLL, 1L ibrutinib use was associated with significantly longer TTNT versus that of 1L CIT. Similarly, early treatment with ibrutinib was associated with longer TTNT as compared to ibrutinib use in later lines of therapy. Moreover, 1L ibrutinib was associated with lower HRU and medical costs compared with 1L CIT, completely offsetting the higher pharmacy costs related to 1L ibrutinib treatment.