Treatment Patterns Among Adults with Newly Diagnosed Primary Immune Thrombocytopenia in the United States

Introduction: Immune thrombocytopenia (ITP) is a rare platelet disorder that can lead to an increased tendency to bleed. Recommended first-line therapies include corticosteroids, intravenous immunoglobulin (IVIg) and intravenous (IV) anti-D. An estimated two-thirds of adult patients with ITP will develop persistent or chronic disease (ITP lasting 3-12 months or >12 months, respectively). Several evidence-based options for second-line treatment exist, but no randomized trials have directly compared one therapy to another. Patterns of treatment in routine clinical practice therefore vary. There is a paucity of data on current real-world treatment dynamics in ITP, and such data could help identify gaps in care and inform future studies of real-world comparative effectiveness and safety. We described the types of treatments administered following an ITP diagnosis, as well as the subsequent occurrence of bleeding and requirement for rescue therapy among adults being managed in routine practice in the United States (US).

Methods: We used electronic health record data from hematology clinics across the US (Flatiron Health, Inc.) linked to MarketScan® employer-based and Medicare Supplemental administrative health insurance claims databases (Truven Health Analytics, Inc.). We included patients aged 18 years or older with a new ITP diagnosis from January 1, 2011 through June 30, 2016, continuous enrollment in MarketScan prior to diagnosis, and no previous diagnosis of a secondary cause of thrombocytopenia. The cumulative incidence of each ITP treatment after diagnosis was estimated using competing risk models to account for deaths occurring before initiation. Estimates were provided specifically for 90 days and 1 year following diagnosis to describe treatment uptake in the newly diagnosed and persistent phases, respectively. The incidence of bleeding events and rescue therapy was quantified after the start of the more prevalent second-line therapies: rituximab, splenectomy, and thrombopoietin receptor agonists (TPO RAs) - eltrombopag and romiplostim. Rescue therapies (those that rapidly increase platelet counts in the setting of severe thrombocytopenia or active bleeding) included IV anti-D, IVIg, IV steroids, and platelet transfusions.

Results: Among the cohort of 447 adults diagnosed with primary ITP, 47% were male, 61% were white, 32% were 65 years or older, and the median lowest platelet count in the 60 days prior to diagnosis was 85x10⁹/L (IQR: 39, 125). Use of each ITP therapy by 90 days and 12 months post-diagnosis are provided in the Table. Oral corticosteroids were the most commonly used; the cumulative incidence of initiation was 41% by 90 days and 50% by 1 year following ITP diagnosis. IV steroids and rituximab were the next most frequently used medications (16% and 11% at 90 days; and 26% and 16% by 1 year, respectively). The cumulative incidence of the TPO RAs, eltrombopag and romiplostim, by 90 days was 3% and 7%, respectively, and by 1 year was 5% and 9%, respectively. Splenectomy was relatively rare (<4% by 1 year) as was use of all other non-rescue ITP medications (≤1% by 1 year). At 180 days post-ITP treatment initiation, rituximab initiators (N = 84) had a slightly lower incidence of bleeding overall (12% [6, 20]) than the other treatment groups (17% [6, 33] among 31 eltrombopag initiators; 19% [9, 31] among 49 romiplostim initiators; and 19% [6, 38] among 21 splenectomized patients). However, rituximab initiators had the highest cumulative incidence of rescue therapy use (48% [36, 58] compared with 29% [14, 46] for eltrombopag, 26% [14, 39] for romiplostim, and 19% [6, 39] for splenectomized patients). Subsequent oral steroid use was less frequent among TPO RA initiators than rituximab initiators or patients who underwent splenectomy.

Conclusions: In this descriptive study of patients with primary ITP receiving care in the US, oral steroids were the most commonly used medication after diagnosis, reflecting their continued role as a frontline therapy. By 1 year after diagnosis, approximately 15% received rituximab, nearly 10% received romiplostim, and 5% received eltrombopag. Splenectomy was less common. Among the medical treatments, although bleeding risk overall appeared lowest in rituximab patients, oral steroid and rescue therapy use were lowest among the patients who initiated TPO RAs.

Table.

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