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Multicenter study of romiplostim for CIT
A Figure 2. Median weekly platelet counts for patients on romi- plostim chemotherapy-induced thrombocytopenia (CIT) treat- ment pathway. (A) Solid tumor patients (n=153). Error bars rep- resent interquartile ranges. (B) Solid tumor patients with no pre- dictors of romiplostim non- response (n=122, blue); solid tumor patients with predictors of romiplostim non-response (n=31, gray) including bone marrow (BM) invasion by tumor, prior pelvic irradiation, or prior temozolomide treatment; aggressive lymphoma patients (n=13, red); and myelo- ma patients (n=7, purple). Error bars omitted for figure clarity. PNR: predictors of romiplostim non-response (includes BM inva- sion by tumor, prior temozolo- mide exposure, or prior pelvic
B
irradiation).
weekly romiplostim dosing pathway and 73 were treated on the intracycle romiplostim dosing pathway (Figure 1). Table 4 describes differences in clinical and platelet count outcome between the two groups. Patients receiving weekly dosing had a significantly higher median platelet count on romiplostim (143x109/L vs. 106x109/L; P<0.001) and a higher rate of achieving a romiplostim response (81% vs. 63%; P=0.006). Figure 3 illustrates the difference in median weekly platelet counts for each cohort. Using negative binomial regression modeling controlling for demographics and predictors of romiplostim non- response, intracycle dosing had higher rates of platelet counts measured <50x109/L, <75x109/L, or <100x109/L (see Table 4 for details), chemotherapy intensity reduction (incidence rate ratio [IRR] 3.00, 95%CI: 1.30-6.91; P=0.010), and bleeding (IRR 4.84, 95%CI: 1.18-19.89; P=0.029) compared with weekly dosing, with similar rates of thromboembolism and platelet transfusion for chemotherapy administration.
Outcomes in hematologic malignancy patients
Median individual patient platelet counts on romi- plostim were significantly higher than at baseline:
46x109/L vs. 21x109/L; P=0.003. Figure 2B illustrates medi- an weekly platelet counts on romiplostim support for hematologic malignancy patients. The rate of romiplostim response in hematologic malignancy patients was 10%. Seven of 20 hematologic malignancy patients (35%) achieved a platelet count ≥100x109/L on romiplostim ther- apy, with a median time to platelet count ≥100x109/L of 24 days (IQR 19-36 days).
In the 20 hematologic malignancy patients treated (for 3.0 patient-years), there were nine chemotherapy intensi- ty reduction events, one bleeding event (which was not fatal), 44 platelet transfusion events, and no thrombotic events.
Additional data on platelet count outcomes and the bleeding event in hematologic malignancy patients are given in Online Supplementary Tables S2 and S3, respec- tively.
Discussion
Initial studies of platelet growth factors to manage CIT utilized the first-generation thrombopoietic agents rhIL-11
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