What is the proper threshold for platelet transfusion in patients with chemotherapy-induced thrombocytopenia?

Quantitation of phosphatidylserine-exposing platelets and platelet-derived microparticles in platelet products: A new strategy to improve efficacy of platelet transfusion

Platelet transfusion is an effective therapy to prevent or treat bleeding. Considering the different clinical purposes of transfusion, it is necessary to assess the quality of platelet products prepared in transfusion laboratories. So far, there is no solution to the problem of how best to do this. Here, we summarize the quantitation of phosphatidylserine (PS)-exposing platelets and platelet-derived microparticles (PMPs) in platelet products using previously reported data. Because PS promotes the assembly and enhances the activity of coagulation factors, classifying platelet products according to their concentrations of PS-exposing platelets and PMPs will improve the therapeutic treatment of transfusion recipients.

Italian daily platelet transfusion practice for haematological patients undergoing high dose chemotherapy with or without stem cell transplantation: a survey by the GIMEMA Haemostasis and Thrombosis Working Party

BACKGROUND

Following high-dose chemotherapy/bone marrow transplantation, patients are routinely, prophylactically transfused with platelet concentrates (PC) if they have a platelet count ≤10×10⁹/L or higher in the presence of risk factors for bleeding. However, whether such transfusions are necessary in clinically stable patients with no bleeding, or whether a therapeutic transfusion strategy could be sufficient and safe, is still debated.

MATERIALS AND METHODS

The GIMEMA Haemostasis and Thrombosis Working Party sent a questionnaire to Italian haematology departments to survey several aspects of daily platelet transfusion practice, such as the cut-off platelet count for transfusion, the evaluation of refractoriness and the type of PC administered.

RESULTS

The questionnaire was answered by 18 out of 31 centres (58%). A total of 23,162 PC were transfused in 2,396 patients in 2013. The vast majority of centres (95%) transfused PC according to Italian and international guidelines; only a few transfused always at platelet counts ≤20×10⁹/L. The broad agreement on platelet count cut-off for transfusion (≤10×10⁹/L) was not confirmed when the World Health Organization (WHO) bleeding score was considered: only a third of centres (33%) used transfusions as recommended when the bleeding grade was ≥2. Platelet refractoriness was poorly monitored and most centres (89%) evaluated, mostly empirically (67%), response to transfusion only 24 hours later. Thirty percent of centres transfused platelets in asymptomatic refractory patients.

DISCUSSION

Although most Italian haematology departments transfuse PC according to Italian and international guidelines, our survey shows that in routine daily practice physicians do not comply closely with the WHO recommendations on platelet transfusions and monitoring platelet refractoriness. This causes excessive platelet transfusions, with a resulting increase of costs and waste of public health resources.

Genetic engineering of platelets to neutralize circulating tumor cells

Mounting experimental evidence demonstrates that platelets support cancer metastasis. Within the circulatory system, platelets guard circulating tumor cells (CTCs) from immune elimination and promote their arrest at the endothelium, supporting CTC extravasation into secondary sites. Neutralization of CTCs in blood circulation can potentially attenuate metastases to distant organs. Therefore, extensive studies have explored the blockade of platelet-CTC interactions as an anti-metastatic strategy. Such an intervention approach, however, may cause bleeding disorders since the platelet-CTC interactions inherently rely on the blood coagulation cascade including platelet activation. On the other hand, platelets have been genetically engineered to correct inherited bleeding disorders in both animal models and human clinical trials. In this study, inspired by the physical association between platelets and CTCs, platelets were genetically modified to express surface-bound tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a cytokine known to induce apoptosis specifically in tumor cells. The TRAIL-expressing platelets were demonstrated to kill cancer cells in vitro and significantly reduce metastases in a mouse model of prostate cancer metastasis. Our results suggest that using platelets to produce and deliver cancer-specific therapeutics can provide a Trojan-horse strategy of neutralizing CTCs to attenuate metastasis.

Comparison of different platelet count thresholds to guide administration of prophylactic platelet transfusion for preventing bleeding in people with haematological disorders after myelosuppressive chemotherapy or stem cell transplantation

BACKGROUND

Platelet transfusions are used in modern clinical practice to prevent and treat bleeding in people who are thrombocytopenic due to bone marrow failure. Although considerable advances have been made in platelet transfusion therapy in the last 40 years, some areas continue to provoke debate, especially concerning the use of prophylactic platelet transfusions for the prevention of thrombocytopenic bleeding.This is an update of a Cochrane review first published in 2004, and previously updated in 2012 that addressed four separate questions: prophylactic versus therapeutic-only platelet transfusion policy; prophylactic platelet transfusion threshold; prophylactic platelet transfusion dose; and platelet transfusions compared to alternative treatments. This review has now been split into four smaller reviews looking at these questions individually; this review compares prophylactic platelet transfusion thresholds.

OBJECTIVES

To determine whether different platelet transfusion thresholds for administration of prophylactic platelet transfusions (platelet transfusions given to prevent bleeding) affect the efficacy and safety of prophylactic platelet transfusions in preventing bleeding in people with haematological disorders undergoing myelosuppressive chemotherapy or haematopoietic stem cell transplantation (HSCT).

SEARCH METHODS

We searched for randomised controlled trials (RCTs) in the Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Library 2015, Issue 6, 23 July 2015), MEDLINE (from 1946), Embase (from 1974), CINAHL (from 1937), the Transfusion Evidence Library (from 1950), and ongoing trial databases to 23 July 2015.

SELECTION CRITERIA

We included RCTs involving transfusions of platelet concentrates, prepared either from individual units of whole blood or by apheresis, and given to prevent bleeding in people with haematological disorders (receiving myelosuppressive chemotherapy or undergoing HSCT) that compared different thresholds for administration of prophylactic platelet transfusions (low trigger (5 x 10(9)/L); standard trigger (10 x 10(9)/L); higher trigger (20 x 10(9)/L, 30 x 10(9)/L, 50 x 10(9)/L); or alternative platelet trigger (for example platelet mass)).

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by Cochrane.

MAIN RESULTS

Three trials met our predefined inclusion criteria and were included for analysis in the review (499 participants). All three trials compared a standard trigger (10 x 10(9)/L) versus a higher trigger (20 x 10(9)/L or 30 x 10(9)/L). None of the trials compared a low trigger versus a standard trigger or an alternative platelet trigger. The trials were conducted between 1991 and 2001 and enrolled participants from fairly comparable patient populations.The original review contained four trials (658 participants); in the previous update of this review we excluded one trial (159 participants) because fewer than 80% of participants had a haematological disorder. We identified no new trials in this update of the review.Overall, the methodological quality of the studies was low across different outcomes according to GRADE methodology. None of the included studies were at low risk of bias in every domain, and all the included studies had some threats to validity.Three studies reported the number of participants with at least one clinically significant bleeding episode within 30 days from the start of the study. There was no evidence of a difference in the number of participants with a clinically significant bleeding episode between the standard and higher trigger groups (three studies; 499 participants; risk ratio (RR) 1.35, 95% confidence interval (CI) 0.95 to 1.90; low-quality evidence).One study reported the number of days with a clinically significant bleeding event (adjusted for repeated measures). There was no evidence of a difference in the number of days of bleeding per participant between the standard and higher trigger groups (one study; 255 participants; relative proportion of days with World Health Organization Grade 2 or worse bleeding (RR 1.71, 95% CI 0.84 to 3.48, P = 0.162; authors' own results; low-quality evidence).Two studies reported the number of participants with severe or life-threatening bleeding. There was no evidence of any difference in the number of participants with severe or life-threatening bleeding between a standard trigger level and a higher trigger level (two studies; 421 participants; RR 0.99, 95% CI 0.52 to 1.88; low-quality evidence).Only one study reported the time to first bleeding episode. There was no evidence of any difference in the time to the first bleeding episode between a standard trigger level and a higher trigger level (one study; 255 participants; hazard ratio 1.11, 95% CI 0.64 to 1.91; low-quality evidence).Only one study reported on all-cause mortality within 30 days from the start of the study. There was no evidence of any difference in all-cause mortality between standard and higher trigger groups (one study; 255 participants; RR 1.78, 95% CI 0.83 to 3.81; low-quality evidence).Three studies reported on the number of platelet transfusions per participant. Two studies reported on the mean number of platelet transfusions per participant. There was a significant reduction in the number of platelet transfusions per participant in the standard trigger group (two studies, mean difference -2.09, 95% CI -3.20 to -0.99; low-quality evidence).One study reported on the number of transfusion reactions. There was no evidence to demonstrate any difference in transfusion reactions between the standard and higher trigger groups (one study; 79 participants; RR 0.07, 95% CI 0.00 to 1.09).None of the studies reported on quality of life.

AUTHORS' CONCLUSIONS

In people with haematological disorders who are thrombocytopenic due to myelosuppressive chemotherapy or HSCT, we found low-quality evidence that a standard trigger level (10 x 10(9)/L) is associated with no increase in the risk of bleeding when compared to a higher trigger level (20 x 10(9)/L or 30 x 10(9)/L). There was low-quality evidence that a standard trigger level is associated with a decreased number of transfusion episodes when compared to a higher trigger level (20 x 10(9)/L or 30 x 10(9)/L).Findings from this review were based on three studies and 499 participants. Without further evidence, it is reasonable to continue with the current practice of administering prophylactic platelet transfusions using the standard trigger level (10 x 10(9)/L) in the absence of other risk factors for bleeding.

Different doses of prophylactic platelet transfusion for preventing bleeding in people with haematological disorders after myelosuppressive chemotherapy or stem cell transplantation

BACKGROUND

Platelet transfusions are used in modern clinical practice to prevent and treat bleeding in people who are thrombocytopenic due to bone marrow failure. Although considerable advances have been made in platelet transfusion therapy in the last 40 years, some areas continue to provoke debate, especially concerning the use of prophylactic platelet transfusions for the prevention of thrombocytopenic bleeding.This is an update of a Cochrane review first published in 2004, and updated in 2012 that addressed four separate questions: prophylactic versus therapeutic-only platelet transfusion policy; prophylactic platelet transfusion threshold; prophylactic platelet transfusion dose; and platelet transfusions compared to alternative treatments. This review has now been split into four smaller reviews; this review compares different platelet transfusion doses.

OBJECTIVES

To determine whether different doses of prophylactic platelet transfusions (platelet transfusions given to prevent bleeding) affect their efficacy and safety in preventing bleeding in people with haematological disorders undergoing myelosuppressive chemotherapy with or without haematopoietic stem cell transplantation (HSCT).

SEARCH METHODS

We searched for randomised controlled trials in the Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Library 2015, Issue 6), MEDLINE (from 1946), Embase (from 1974), CINAHL (from 1937), the Transfusion Evidence Library (from 1950), and ongoing trial databases to 23 July 2015.

SELECTION CRITERIA

Randomised controlled trials involving transfusions of platelet concentrates, prepared either from individual units of whole blood or by apheresis, and given to prevent bleeding in people with malignant haematological disorders or undergoing HSCT that compared different platelet component doses (low dose 1.1 x 10(11)/m(2) ± 25%, standard dose 2.2 x 10(11)/m(2) ± 25%, high dose 4.4 x 10(11)/m(2) ± 25%).

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by The Cochrane Collaboration.

MAIN RESULTS

We included seven trials (1814 participants) in this review; six were conducted during one course of treatment (chemotherapy or HSCT).Overall the methodological quality of studies was low to moderate across different outcomes according to GRADE methodology. None of the included studies were at low risk of bias in every domain, and all the included studies had some threats to validity.Five studies reported the number of participants with at least one clinically significant bleeding episode within 30 days from the start of the study. There was no difference in the number of participants with a clinically significant bleeding episode between the low-dose and standard-dose groups (four studies; 1170 participants; risk ratio (RR) 1.04, 95% confidence interval (CI) 0.95 to 1.13; moderate-quality evidence); low-dose and high-dose groups (one study; 849 participants; RR 1.02, 95% CI 0.93 to 1.11; moderate-quality evidence); or high-dose and standard-dose groups (two studies; 951 participants; RR 1.02, 95% CI 0.93 to 1.11; moderate-quality evidence).Three studies reported the number of days with a clinically significant bleeding event per participant. There was no difference in the number of days of bleeding per participant between the low-dose and standard-dose groups (two studies; 230 participants; mean difference -0.17, 95% CI -0.51 to 0.17; low quality evidence). One study (855 participants) showed no difference in the number of days of bleeding per participant between high-dose and standard-dose groups, or between low-dose and high-dose groups (849 participants).Three studies reported the number of participants with severe or life-threatening bleeding. There was no difference in the number of participants with severe or life-threatening bleeding between a low-dose and a standard-dose platelet transfusion policy (three studies; 1059 participants; RR 1.33, 95% CI 0.91 to 1.92; low-quality evidence); low-dose and high-dose groups (one study; 849 participants; RR 1.20, 95% CI 0.82 to 1.77; low-quality evidence); or high-dose and standard-dose groups (one study; 855 participants; RR 1.11, 95% CI 0.73 to 1.68; low-quality evidence).Two studies reported the time to first bleeding episodes; we were unable to perform a meta-analysis. Both studies (959 participants) individually found that the time to first bleeding episode was either the same, or longer, in the low-dose group compared to the standard-dose group. One study (855 participants) found that the time to the first bleeding episode was the same in the high-dose group compared to the standard-dose group.Three studies reported all-cause mortality within 30 days from the start of the study. There was no difference in all-cause mortality between treatment arms (low-dose versus standard-dose: three studies; 1070 participants; RR 2.04, 95% CI 0.70 to 5.93; low-quality evidence; low-dose versus high-dose: one study; 849 participants; RR 1.33, 95% CI 0.50 to 3.54; low-quality evidence; and high-dose versus standard-dose: one study; 855 participants; RR 1.71, 95% CI 0.51 to 5.81; low-quality evidence).Six studies reported the number of platelet transfusions; we were unable to perform a meta-analysis. Two studies (959 participants) out of three (1070 participants) found that a low-dose transfusion strategy led to more transfusion episodes than a standard-dose. One study (849 participants) found that a low-dose transfusion strategy led to more transfusion episodes than a high-dose strategy. One study (855 participants) out of three (1007 participants) found no difference in the number of platelet transfusions between the high-dose and standard-dose groups.One study reported on transfusion reactions. This study's authors suggested that a high-dose platelet transfusion strategy may lead to a higher rate of transfusion-related adverse events.None of the studies reported quality-of-life.

AUTHORS' CONCLUSIONS

In haematology patients who are thrombocytopenic due to myelosuppressive chemotherapy or HSCT, we found no evidence to suggest that a low-dose platelet transfusion policy is associated with an increased bleeding risk compared to a standard-dose or high-dose policy, or that a high-dose platelet transfusion policy is associated with a decreased risk of bleeding when compared to a standard-dose policy.A low-dose platelet transfusion strategy leads to an increased number of transfusion episodes compared to a standard-dose strategy. A high-dose platelet transfusion strategy does not decrease the number of transfusion episodes per participant compared to a standard-dose regimen, and it may increase the number of transfusion-related adverse events.Findings from this review would suggest a change from current practice, with low-dose platelet transfusions used for people receiving in-patient treatment for their haematological disorder and high-dose platelet transfusion strategies not being used routinely.

A therapeutic-only versus prophylactic platelet transfusion strategy for preventing bleeding in patients with haematological disorders after myelosuppressive chemotherapy or stem cell transplantation

BACKGROUND

Platelet transfusions are used in modern clinical practice to prevent and treat bleeding in thrombocytopenic patients with bone marrow failure. Although considerable advances have been made in platelet transfusion therapy in the last 40 years, some areas continue to provoke debate, especially concerning the use of prophylactic platelet transfusions for the prevention of thrombocytopenic bleeding.This is an update of a Cochrane review first published in 2004 and updated in 2012 that addressed four separate questions: therapeutic-only versus prophylactic platelet transfusion policy; prophylactic platelet transfusion threshold; prophylactic platelet transfusion dose; and platelet transfusions compared to alternative treatments. We have now split this review into four smaller reviews looking at these questions individually; this review is the first part of the original review.

OBJECTIVES

To determine whether a therapeutic-only platelet transfusion policy (platelet transfusions given when patient bleeds) is as effective and safe as a prophylactic platelet transfusion policy (platelet transfusions given to prevent bleeding, usually when the platelet count falls below a given trigger level) in patients with haematological disorders undergoing myelosuppressive chemotherapy or stem cell transplantation.

SEARCH METHODS

We searched for randomised controlled trials (RCTs) in the Cochrane Central Register of Controlled Trials (Cochrane Library 2015, Issue 6), MEDLINE (from 1946), Embase (from 1974), CINAHL (from 1937), the Transfusion Evidence Library (from 1950) and ongoing trial databases to 23 July 2015.

SELECTION CRITERIA

RCTs involving transfusions of platelet concentrates prepared either from individual units of whole blood or by apheresis, and given to prevent or treat bleeding in patients with malignant haematological disorders receiving myelosuppressive chemotherapy or undergoing HSCT.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by The Cochrane Collaboration.

MAIN RESULTS

We identified seven RCTs that compared therapeutic platelet transfusions to prophylactic platelet transfusions in haematology patients undergoing myelosuppressive chemotherapy or HSCT. One trial is still ongoing, leaving six trials eligible with a total of 1195 participants. These trials were conducted between 1978 and 2013 and enrolled participants from fairly comparable patient populations. We were able to critically appraise five of these studies, which contained separate data for each arm, and were unable to perform quantitative analysis on one study that did not report the numbers of participants in each treatment arm.Overall the quality of evidence per outcome was low to moderate according to the GRADE approach. None of the included studies were at low risk of bias in every domain, and all the studies identified had some threats to validity. We deemed only one study to be at low risk of bias in all domains other than blinding.Two RCTs (801 participants) reported at least one bleeding episode within 30 days of the start of the study. We were unable to perform a meta-analysis due to considerable statistical heterogeneity between studies. The statistical heterogeneity seen may relate to the different methods used in studies for the assessment and grading of bleeding. The underlying patient diagnostic and treatment categories also appeared to have some effect on bleeding risk. Individually these studies showed a similar effect, that a therapeutic-only platelet transfusion strategy was associated with an increased risk of clinically significant bleeding compared with a prophylactic platelet transfusion policy. Number of days with a clinically significant bleeding event per participant was higher in the therapeutic-only group than in the prophylactic group (one RCT; 600 participants; mean difference 0.50, 95% confidence interval (CI) 0.10 to 0.90; moderate-quality evidence). There was insufficient evidence to determine whether there was any difference in the number of participants with severe or life-threatening bleeding between a therapeutic-only transfusion policy and a prophylactic platelet transfusion policy (two RCTs; 801 participants; risk ratio (RR) 4.91, 95% CI 0.86 to 28.12; low-quality evidence). Two RCTs (801 participants) reported time to first bleeding episode. As there was considerable heterogeneity between the studies, we were unable to perform a meta-analysis. Both studies individually found that time to first bleeding episode was shorter in the therapeutic-only group compared with the prophylactic platelet transfusion group.There was insufficient evidence to determine any difference in all-cause mortality within 30 days of the start of the study using a therapeutic-only platelet transfusion policy compared with a prophylactic platelet transfusion policy (two RCTs; 629 participants). Mortality was a rare event, and therefore larger studies would be needed to establish the effect of these alternative strategies. There was a clear reduction in the number of platelet transfusions per participant in the therapeutic-only arm (two RCTs, 991 participants; standardised mean reduction of 0.50 platelet transfusions per participant, 95% CI -0.63 to -0.37; moderate-quality evidence). None of the studies reported quality of life. There was no evidence of any difference in the frequency of adverse events, such as transfusion reactions, between a therapeutic-only and prophylactic platelet transfusion policy (two RCTs; 991 participants; RR 1.02, 95% CI 0.62 to 1.68), although the confidence intervals were wide.

AUTHORS' CONCLUSIONS

We found low- to moderate-grade evidence that a therapeutic-only platelet transfusion policy is associated with increased risk of bleeding when compared with a prophylactic platelet transfusion policy in haematology patients who are thrombocytopenic due to myelosuppressive chemotherapy or HSCT. There is insufficient evidence to determine any difference in mortality rates and no evidence of any difference in adverse events between a therapeutic-only platelet transfusion policy and a prophylactic platelet transfusion policy. A therapeutic-only platelet transfusion policy is associated with a clear reduction in the number of platelet components administered.

Absolute immature platelet count may predict imminent platelet recovery in thrombocytopenic children following chemotherapy

BACKGROUND

Immature platelets are the youngest circulating platelets and they reflect the rate of thrombopoiesis. The immature platelet fraction (IPF) or the absolute immature platelet count (AIPC) may predict platelet count recovery following chemotherapy-induced thrombocytopenia in pediatric patients and help guiding prophylactic platelet transfusion therapy.

PROCEDURE

To test IPF and AIPC as predictors of platelet recovery, 19 children with platelet nadirs of less than 20 × 10(9)/L after chemotherapy were prospectively enrolled. IPF, platelet count, and C-reactive protein (CRP) were analyzed in 416 paired samples from 37 patients with malignancies to test if IPF-levels were CRP dependent.

RESULTS

A significant increase of 0.6 × 10(9)/L in AIPC was seen between 1 and 2 days prior to platelet count recovery. No predictive day-to-day differences were found for IPF. Platelet count recovery did not occur significantly earlier for patients with a peak IPF > 10% than for those patients with a peak IPF < 10%. IPF and AIPC showed no correlation to CRP. AIPC was in contrast to IPF not influenced by platelet transfusions.

CONCLUSION

AIPC increased significantly between 24 and 48 hours before platelet recovery whereas IPF showed no significant increase during the same time period. AIPC may be a better indicator than IPF for predicting platelet recovery after chemotherapy in pediatric patients.

Oxaliplatin-related thrombocytopenia

Oxaliplatin is a third generation platinum compound that inhibits DNA synthesis, mainly through intrastrandal cross-links in DNA. Most of the experience with the clinical use of this drug is derived from colorectal cancer but it is also used in other tumor types such as ovary, breast, liver and non-Hodgkin's lymphoma. Thrombocytopenia is a frequent toxicity seen during oxaliplatin treatment, occurring at any grade in up to 70% of patients and leading to delays or even discontinuation of the chemotherapy. Although myelossupression is recognized as the main cause of oxaliplatin-related thrombocytopenia, new mechanisms for this side-effect have emerged, including splenic sequestration of platelets related to oxaliplatin-induced liver damage and immune thrombocytopenia. These new pathophysiology pathways have different clinical presentations and evolution and may need specific therapeutic maneuvers. This article attempts to review this topic and provides useful clinical information for the management of oxaliplatin-related thrombocytopenia.

The influence of bleeding on trigger changes for platelet transfusion in patients with chemotherapy-induced thrombocytopenia

BACKGROUND

For patients with thrombocytopenia without bleeding risk factors, a platelet transfusion trigger of 10 × 10(9) /L is recommended. No studies have evaluated the clinicians' decision-making process leading to trigger changes.

STUDY DESIGN AND METHODS

We report on the evaluation of trigger changes and the relation with bleeding. Eighty patients previously enrolled in the SPRINT trial represent the patient population for the current analysis.

RESULTS

Seventy-four patients had a starting trigger of 10 × 10(9) /L. Only a minority of patients treated with chemotherapy alone (3/12, 25%) and autologous transplant (6/15, 40%) had a change in their trigger in contrast to the majority of allogeneic transplant (37/47, 79%; p = 0.001 and p = 0.009, respectively, when compared to allogeneic transplant group). Bleeding was the main reason reported by clinicians for a trigger change, but the occurrence of significant bleeding (Grade 2-4) was similar in patients with or without a trigger change (51 and 54%, p = 1.00). Clinicians were influenced by the bleeding system: grade 1 mucocutaneous bleeding leading to a trigger change was overrepresented (71% of cases), as was grade 2 genitourinary bleeding not leading to a trigger change (57% of cases).

CONCLUSION

A universal trigger of 10 × 10(9) /L may not be maintained in a diverse population of patients with their respective bleeding risk factors. Because the trigger is changed often, it may not be as effective as previously believed.

Clinical findings with the first generation of thrombopoietic agents

Thrombocytopenia is a common problem in hematology/oncology patients. In the past two decades a number of thrombopoietic growth factors and related cytokines have become available for clinical investigations. Unfortunately, most of the pleiotropic cytokines have been limited by their modest activity and toxicity profile. The discovery of thrombopoietin (TPO), a key regulator of platelet production, led to the clinical development of two recombinant versions of the molecule: full-length, recombinant human thrombopoietin (rhTPO), and truncated and pegylated, megakaryocyte growth and development factor (Peg-rHuMGDF). Both agents showed significant biologic activity in various clinical settings, including nonmyeloablative chemotherapy, mobilization of progenitors, platelet apheresis, and treatment of thrombocytopenia related to other conditions. Despite promising thrombopoietic activity, the clinical development of the first generation of recombinant TPOs was discontinued due to the neutralizing antibodies observed with PEG-rHuMGDF. This has led to the development of TPO agonists with no sequence homology to TPO, which can bind to the TPO receptors and activate signaling, leading to an increase in platelet production. The clinical experience with the first generation of thrombopoietic agents has provided insight into the biology and future directions for a second generation of thrombopoietic agents in various disorders of thrombocytopenia.

Increased efficacy of breast cancer chemotherapy in thrombocytopenic mice

Platelets contribute to homeostasis of the tumor vasculature by helping prevent hemorrhage. Thus, we hypothesized that inducing thrombocytopenia would increase tumor vascular leakiness and facilitate the effective delivery of chemotherapeutic agents to tumors. In a mammary carcinoma murine model, platelet depletion induced bleeding specifically at the tumor site, favoring the accumulation of fluorescently labeled microspheres only in the tumor. Moreover, induction of thrombocytopenia in tumor-bearing mice before injection of paclitaxel increased its intratumoral accumulation and reduced growth of both slow- and fast-growing tumors, compared with mice with normal platelet counts that were treated only with paclitaxel. Histologic analysis confirmed the expectation of an increase in tumor apoptosis and a reduction in tumor proliferation in thrombocytopenic mice receiving chemotherapy. No increased toxicity was seen in other organs or blood cells. Taken together, our results indicate that low platelet count selectively induces leakiness of tumor vessels and favors the delivery of chemotherapy to tumor sites, enhancing its tumoricidal effects.

Profound thrombocytopenia and survival of hematopoietic stem cell transplant patients without clinically significant bleeding, using prophylactic platelet transfusion triggers of 10 x 10(9) or 20 x 10(9) per L

BACKGROUND

A trigger of 10 x 10(9) per L for prophylactic platelet (PLT) transfusions is generally recommended for stable thrombocytopenic patients who receive chemotherapy, based on studies showing similar incidence, severity, and fatality of bleeding compared with the 20 x 10(9) per L trigger. The outcome of thrombocytopenic nonbleeding patients has not been well described. This retrospective analysis evaluates thrombocytopenia and survival of 381 hematopoietic stem cell transplant (HSCT) patients without clinically significant bleeding, with 10 x 10(9) and 20 x 10(9) per L prophylactic triggers.

STUDY DESIGN AND METHODS

A total of 170 patients who received prophylactic PLT transfusions at 20 x 10(9) per L (1997-1998, SP1) and 211 patients who had prophylaxis at 10 x 10(9) per L (1999-2001, SP2) were identified as nonbleeding patients. PLT counts and clinical complications were assessed within 100 days from HSCT.

RESULTS

PLT counts less than or equal to 10 x 10(9) per L were found in 69.2 percent of patients in SP2 and 38.3 percent in SP1 (p < 0.001). Profound thrombocytopenia (4+ PLT counts <or=10 x 10(9)/L) was found in 19.0 percent of patients in SP2 and 7.0 percent in SP1 (p = 0.001). Patients with profound thrombocytopenia had significantly increased early mortality (odds ratio [OR], 3.18; 95% confidence interval [CI], 1.25-8.07) and significantly reduced overall survival (hazard ratio [HR], 1.95; 95% CI, 1.28-2.97) compared to patients with 0 to 3 PLT counts less than or equal to 10 x 10(9) per L. The association of profound thrombocytopenia with early mortality was more notable in SP2.

CONCLUSION

The 10 x 10(9) per L transfusion trigger is associated with significantly greater exposure to low PLT counts. Nonbleeding patients with profound thrombocytopenia were at significantly greater risk of dying compared with nonthrombocytopenic patients. These results suggest that safety of the 10 x 10(9) per L trigger should be more thoroughly evaluated.

Acute bleeding complications in patients after hematopoietic stem cell transplantation with prophylactic platelet transfusion triggers of 10�נ109and 20�נ109per L

BACKGROUND

Prophylactic platelet (PLT) transfusions are given as a standard care in patients with hematologic malignancies undergoing hematopoietic stem cell transplantation (HSCT). This retrospective analysis evaluates utilization of blood transfusions, risk of bleeding, and survival in 480 HSCT patients at 10 x 10(9) and 20 x 10(9) per L prophylactic trigger levels.

STUDY DESIGN AND METHODS

A total of 224 patients received prophylactic PLT transfusions at 20 x 10(9) per L threshold (1997-1998, SP1); 256 patients had prophylaxis at 10 x 10(9) per L (1999-2001, SP2). Bleeding scores were assigned daily.

RESULTS

A slight reduction in PLT transfusions per patient in SP2 compared with SP1 was not statistically significant (odds ratio, 0.82; 95% confidence interval, 0.51-1.33; p = 0.416), yet a significantly higher proportion of patients in SP2 had PLT counts less than or equal to 10 x 10(9) per L compared to SP1 (p < 0.001). In patients who bled, however, there was no excess exposure to low PLT counts before bleeding started. A substantial number of patients who bled received PLT transfusions above the goal before bleeding started (82.9% in SP2, 41.5% in SP1) because of medical complications that associated with increased risk of bleeding. Bleeding incidence was similar in both study periods (21.9% in SP1, 16.4% in SP2; p = 0.526). Bleeding was significantly associated with reduced survival in both study periods.

CONCLUSIONS

Patients who bled were usually placed on a higher threshold before the onset of their major bleeding event and were not exposed to additional risk of bleeding from thrombocytopenia. Similarity in bleeding incidence between study periods appears to associate with adjustments to high-risk conditions and may not reflect consequences of the lower transfusion threshold.

Feasibility and usefulness of self-assessment of bleeding in patients with haematological malignancies, and the association between platelet count and bleeding

BACKGROUND AND OBJECTIVES

The aim of this study was to evaluate the collection of daily prospective information about bleeding outcomes in patients with thrombocytopenia, including information obtained by patient self-assessment.

MATERIALS AND METHODS

Consecutive patients with haematological malignancies were enrolled in a study of bleeding data collection during the period of thrombocytopenia. A short educational session and information sheet was designed for self-assessment. Platelet counts and all transfusions were recorded daily. Bleeding scores were translated into World Health Organization (WHO) bleeding grades.

RESULTS

Nineteen patients were included in the study. Four-hundred and ten days of thrombocytopenia were eligible for assessment of bleeds. Self-assessment was feasible, as defined by the total proportion of days on which self-assessment was completed (70%, 288 thrombocytopenic days). There was 86% agreement between bleeding data collected by self-assessment and by medical examination using a structured assessment form. Examples of discrepancies included the duration of petechiae/bruises and the reporting of minor bleeding. There was no evidence for an association between patients' morning platelet count and daily WHO bleeding grade. The incidences of WHO grade 1 and grade 2 bleeding on days with platelet counts < or = 10 x 10(9)/l, 11-20 x 10(9)/l, and > 20 x 10(9)/l were similar and did not reveal higher rates of bleeding at lower counts.

CONCLUSIONS

Patient self-assessment can help to support comprehensive daily prospective monitoring of bleeding, specifically facilitating data collection following hospital discharge. The discrepancies between self-assessment and medical examination highlight the need to develop a validated international assessment tool. The association among platelet count, risk of bleeding and role of prophylactic platelet transfusions needs further evaluation in larger prospective trials.

Platelet transfusion prophylaxis for patients with haematological malignancies: where to now?

National guidelines for platelet transfusion in many countries recommend that the general platelet transfusion trigger for prophylaxis is 10x10(9)/l. This annotation reviews the evidence for this threshold level and discusses other current unresolved issues relevant to platelet transfusion practice such as the optimal dose and the clinical benefit of a strategy for the prophylactic use of platelet transfusions when the platelet count falls below a given threshold.

Intraarterial Platelet Infusion for Patients with Intractable Gastrointestinal Hemorrhage and Severe Refractory Thrombocytopenia

Transarterial therapies used for the treatment of acute nonvariceal gastrointestinal (GI) hemorrhage have traditionally included vasopressin infusion and embolization. However, for patients with diffuse or multifocal hemorrhage and severe refractory thrombocytopenia, these options are suboptimal because platelet counts and coagulation parameters may not be adequate to allow for the formation of a stable clot. Herein two such patients treated with direct intraarterial (IA) infusion of platelets into the vascular territory supplying the hemorrhage are described. In both patients, after IA platelet infusion, blood product requirements were immediately reduced, bleeding from the GI tract resolved by clinical and laboratory criteria, and no significant bowel ischemia was seen.

Triggers for prophylactic use of platelet transfusions and optimal platelet dosing in thrombocytopenic dogs and cats

Prophylactic platelet transfusions are frequently given to human patients with hypoproliferative thrombocytopenia. For several decades, the most common transfusion trigger was 20,000/microL, but the trend is now to use 10,000/microL in the absence of other risk factors for bleeding. This trigger seems to reduce the number of transfusions without increasing the risk of severe bleeding. Most studies involved in establishing platelet transfusion policies have involved patients with acute leukemia, with fewer studies involving patients undergoing hematopoietic stem cell transplantation or aggressive chemotherapy for other cancers and patients with aplastic anemia. In the presence of other risk factors for spontaneous bleeding, 20,000/microL is still considered an appropriate trigger. The trigger for prophylactic transfusion before surgery has not undergone the same recent scrutiny as has the trigger for spontaneous bleeding. The recommendation remains to raise the platelet count to 50,000 to 100,000/microL if possible, although it is recognized that surgery and other invasive procedures have been performed at lower platelet counts without major bleeding. Prophylactic transfusion is not used in disorders of platelet consumption and destruction to prevent spontaneous bleeding but is used before surgery. Because of the comparative lack of experience with platelet transfusion in veterinary medicine, it is difficult to make generalizations for dogs and cats. Using the guidelines established for therapeutic and prophylactic transfusion of human patients is a reasonable starting point, however. A therapeutic transfusion policy is suggested in the veterinary setting provided that the patient can be closely observed for critical bleeding and a prompt transfusion can be given. This policy should ultimately reduce the overall number of platelet transfusions given to hospital patients. If an animal cannot be closely observed or the ability to transfuse on demand is limited, prophylactic transfusion is recommended. The triggers for initiating a platelet transfusion in dogs are extrapolated from human data; these values are lower by 50% for cats. Because of the imprecision of platelet counting at low values, platelet counts must always be interpreted in conjunction with clinical signs of hemorrhage. If platelet-rich plasma or platelet concentrate is available, a dose of 1 platelet unit per 10 kg is recommended, although resources may dictate a smaller dose. This will raise the recipient platelet count by a maximum of about 40,000/microL. Assuming a trigger of 10,000/microL, a transfusion will probably be required approximately every 3 days. It must be remembered that the frequency of platelet transfusions may be greater in the presence of factors accelerating platelet loss or destruction. If fresh whole blood is used, a rule of thumb is to transfuse 10 mL/kg, which will raise the recipient platelet count by a maximum of approximately 10,000/microL. Daily transfusions or transfusions every other day will probably be required.