Thrombin generation and cell-dependent hypercoagulability in sickle cell disease

Essentials Sickle cell disease is increasingly being recognized as a chronic hypercoagulable state. Thrombin generation is elevated in the whole blood, but not the plasma of sickle cell patients. Whole blood thrombin generation inversely correlates to erythrocyte phosphatidylserine exposure. Acquired protein S deficiency is likely explained by binding of protein S to sickle red cells. Click to hear Dr Hillery discuss coagulation and vascular pathologies in mouse models of sickle cell disease.

SUMMARY

Introduction Sickle cell disease (SCD) is a hypercoagulable state with chronic activation of coagulation and an increased incidence of thromboembolic events. However, although plasma pre-thrombotic markers such as thrombin-anithrombin complexes and D-dimer are elevated, there is no consensus on whether global assays of thrombin generation in plasma are abnormal in patients with SCD. Based on our recent observation that normal red blood cells (RBCs) contribute to thrombin generation in whole blood, we hypothesized that the cellular components in blood (notably phosphatidylserine-expressing erythrocytes) contribute to enhanced thrombin generation in SCD. Methods Whole blood and plasma thrombin generation assays were performed on blood samples from 25 SCD patients in a non-crisis 'steady state' and 25 healthy race-matched controls. Results Whole blood thrombin generation was significantly elevated in SCD, whereas plasma thrombin generation was paradoxically reduced compared with controls. Surprisingly, whole blood and plasma thrombin generation were both negatively correlated with phosphatidylserine exposure on RBCs. Plasma thrombin generation in the presence of exogenous activated protein C or soluble thrombomodulin revealed deficiencies in the protein C/S anticoagulant pathway in SCD. These global changes were associated with significantly lower plasma protein S activity in SCD that correlated inversely with RBC phosphatidylserine exposure. Conclusion Increased RBC phosphatidylserine exposure in SCD is associated with acquired protein S deficiency. In addition, these data suggest a cellular contribution to thrombin generation in SCD (other than RBC phosphatidylserine exposure) that explains the elevated thrombin generation in whole blood.

Abstract P3-06-07: Ki67 as a Predictive Marker of Response to Neoadjuvant Chemotherapy in Patients with Early-Stage Breast Cancer (ESBC): A Systematic Review and Evidence Summary

Background: Immunohistochemical (IHC) assessment of the proportion of cells staining for the KI67 nuclear antigen is being increasing utilized in the management of patients with early-stage breast cancer (ESBC). A comprehensive systematic review and evidence synthesis of biomarkers potentially predictive of response to systemic therapy was initiated as a part of an NCI-funded comparative effectiveness research program.

Methods: Studies of chemotherapy response prediction based on baseline IHC assessment of Ki67 in patients with ESBC receiving neoadjuvant systemic therapy were identified. Response was specified as pathologic complete response (pCR) or clinical response (ClinR). Assay predictive performance for response was assessed on the basis of sensitivity, specificity, predictive value and predictive odds ratio (POR±95%CLs) utilizing mixed effects models. Study results were fitted in an ROC analysis based on the method of DerSimonian and Laird. Publication bias was evaluated on the basis of funnel plot asymmetry assessed by Egger's regression intercept and Begg and Mazumdar's rank correlation.

Results: Of 469 potentially eligible studies, dual blind full text review identified 42 eligible studies reporting 44 independent cohorts with 6,716 patients (21–979). While Ki67 cutpoints varied considerably, they were most commonly between 10%–30% (median 20%, range 1–50%). The analysis prsented here is limited to the 30 studies of ESBC patients (N = 3,343) receiving neoadjuvant therapy of which 14 reported fewer than 100 patients. The proportion of patients with elevated Ki67 across studies ranged from 0.20–0.92 (median = 0.54). Sensitivity and specificity for treatment response in patients with high vs. low baseline Ki67 was 0.65 [0.61, 0.68] and 0.52 [0.50, 0.54], respectively. Estimated response rates across studies in patients with high vs. low Ki67 were 31% [29%, 34%] and 19% [17%, 21%], respectively. The estimated POR for response across studies was 2.82 [2.14, 3.72; P < .001].

Abstract P1-15-04: The relationship of relative dose intensity and supportive care to febrile neutropenia rates in patients with early stage breast cancer receiving chemotherapy: a prospective cohort study of chemotherapy-associated toxicity

Background: Febrile neutropenia (FN) represents a major dose-limiting toxicity of cancer chemotherapy resulting in considerable morbidity, mortality, and cost. Patients have the highest risk of the initial neutropenic event in cycle 1 when most patients receive full dose chemotherapy. This study evaluates time course of neutropenic events in patients receiving chemotherapy for early-stage breast cancer (ESBC) and supportive care interventions that modify FN risk in ESBC patients treated in actual oncology practice.

Methods: A prospective cohort study of adult cancer patients with solid tumors or lymphoma starting a chemotherapy regimen was conducted at 115 U.S. sites. Toxicities associated with chemotherapy were recorded in up to 4 cycles including severe neutropenia (SN), FN, and infection. Documented clinical interventions included reductions in chemotherapy relative dose intensity (RDI), the use of colony-stimulating factors (CSFs), and antibiotics.

Results: A total of 1202 ESBC patients starting chemotherapy were analyzed, of which 1154, 1099, and 896 reached the midcycle of cycles 2, 3, and 4, respectively. While the majority of neutropenic and infection events occurred in cycle 1, decreasing rates of FN and infection in later cycles correlated with increasing reductions in dose intensity and increased use of CSFs and antibiotics.