Colony-stimulating factors for the management of neutropenia in cancer patients

Natural resistance, iron and infection: a challenge for clinical medicine

Natural resistance to infection, which does not depend on antibiotics, is a powerful protective mechanism common to all mankind that has been responsible for the survival of our species during countless millennia in the past. The normal functioning of this complex system of phagocytic cells and tissue fluids is entirely dependent on an extremely low level of free ionic iron (10(-18) M) in tissue fluids. This low-iron environment is maintained by the unsaturated iron-binding proteins transferrin and lactoferrin, which depend on well-oxygenated tissues, where a relatively high oxidation-reduction potential (Eh) and pH are essential for the binding of ferric iron. Freely available iron is derived from iron overload, free haem compounds, or hypoxia in injured tissue leading to a fall in Eh and pH. This can severely damage or abolish normal bactericidal mechanisms in tissue fluids leading to overwhelming growth of bacteria or fungi. The challenge for clinical medicine is to reduce or eliminate the presence of freely available iron in clinical disease. In injured or hypoxic tissue, treatment with hyperbaric oxygen might prove very useful by increasing tissue oxygenation and restoring normal bactericidal mechanisms in tissue fluids, which would be of huge benefit to the patient.

Prevention of severe menorrhagia in oncology patients with treatment-induced thrombocytopenia by luteinizing hormone-releasing hormone agonist and depo-medroxyprogesterone acetate

BACKGROUND

Menorrhagia is a serious complication in young female oncology patients who suffer from severe thrombocytopenia during myelosuppressive treatment. To the authors' knowledge, little is known regarding the incidence of this complication or the effectiveness of possible therapies for its prevention.

METHODS

In this retrospective clinical study, after a thorough gynecologic evaluation, young female oncology patients with regular menstrual cycles undergoing myelosuppressive treatments received either depo-medroxyprogesterone acetate (DMPA), or D-tryptophan-6-luteinizing hormone-releasing hormone depot treatment (gonadotropin-releasing hormone agonist [GnRH-a]), or no treatment before the administration of myelosuppresive chemotherapy. Only patients who later developed severe thrombocytopenia (<25,000 platelets per muL) were included in the study. Daily blood counts, menorrhagia, nonvaginal bleeding episodes, and the need for blood products, gynecologic consultations, and other medical interventions were determined.

RESULTS

Of 101 women with cancer who met the inclusion criteria, 42 patients received DMPA, 39 patients received GnRH-a, and 20 patients remained untreated. The mean duration (+/- standard deviation) of severe thrombocytopenia was 24.76 +/- 23.6 days. Four patients were not included because of significant gynecologic pathologies. General bleeding from nongynecologic sites was similar for all groups and was not associated with vaginal bleeding. Severe or moderate menorrhagia was documented in none of the 39 women who received GnRH-a, in 9 patients (21.4%) who received DMPA, and in 9 untreated patients (40%; P = .02). Fewer calls for urgent gynecologic consultations were documented in the GnRH-a group compared with the untreated group (P < .0001).

CONCLUSIONS

Female patients undergoing myelosupressive therapy are at high risk of developing significant menorrhagia during prolonged, severe thrombocytopenia. Pretreatment gynecologic evaluation can detect significant pelvic pathologies. GnRH-a treatment effectively prevented menorrhagia, whereas DMPA administration was less effective.

Risk models for predicting chemotherapy-induced neutropenia

Neutropenia and its complications, including febrile neutropenia, are major dose-limiting toxicities of systemic cancer chemotherapy. A number of studies have attempted to identify risk factors for neutropenia and its consequences to develop predictive models capable of identifying patients at greater risk for such complications and to guide more effective and cost-effective applications of the colony-stimulating factors. A systematic review of the literature showed that age, performance status, nutritional status, chemotherapy dose intensity, and low baseline blood cell counts were associated with the risk of severe and febrile neutropenia or reduced chemotherapy dose intensity in multivariate analysis in two or more studies. Similarly, age, diagnosis of leukemia or lymphoma, high temperature or low blood pressure at admission, and i.v. site infection along with low blood cell counts and organ dysfunction were associated with serious medical complications of febrile neutropenia, including bacteremia and death. The available risk model studies, however, had several limitations, including retrospective analyses of small study populations lacking independent validation, frequent missing values, and differences in the predictive factors considered. To overcome the limitations of previous studies, efforts are under way to develop and validate risk models based on large prospective studies in representative populations of patients receiving systemic chemotherapy.

Non-small cell lung cancer treatment-related bone marrow toxicities

A major consequence of administering increasingly aggressive therapies (chemotherapy with or without radiation therapy) in the treatment of non-small cell lung cancer is the adverse effects on the bone marrow that may lead to neutropenia, thrombocytopenia, and/or anemia. Myelosuppression or bone marrow toxicity may also lead to dose reduction of chemotherapy and/or treatment delays in both chemotherapy and radiation therapy, diminishing the efficacy of therapy in the curative setting. In this setting, the use of hematopoietic growth factors may thus be beneficial.

Immune restoration following hematopoietic stem cell transplantation: an evolving target

Hematopoietic stem cell transplantation (HSCT) is the definitive cure for many malignant and nonmalignant diseases. However, delays in immune reconstitution (IR) following HSCT significantly limit the success of transplantation and increase the risk for infection and disease relapse in the transplant recipient. Therefore, ways to measure and to manipulate immune recovery following HSCT are emerging and their success depends directly upon an enhanced understanding for the underlying mechanisms responsible for reconstituted immunity and hematopoiesis. Recent discoveries in the activation, function, and regulation of dendritic cell (DC), natural killer (NK) cell, and T-lymphocyte subtypes have been critical in developing immunotherapies used to prevent graft-versus-host disease and to enhance graft-versus-leukemia. For example, regulatory T cells that induce tolerance and NK receptor-tumor ligand disparities that result in tumor lysis are being used to minimize GVHD and tumor burden, respectively. Furthermore, expansion and modulation of immune effector cells are being used to augment hematopoietic and immune recovery and to decrease transplant-related toxicity in the transplant recipient. Specifically, DC expansion and incorporation into antitumor and anti-microbial vaccines is fast approaching application into clinical trials. This paper will review our current understanding for IR following HSCT and the novel ways in which to restore immune function and decrease transplant-related toxicity in the transplant recipient.

Iron and infection: the heart of the matter

Bacterial resistance to antibiotics is a major threat to clinical medicine. However, natural resistance to bacterial infection, which does not depend on antibiotics, is a powerful protective mechanism common to all mankind. The availability of iron is the heart of the matter and the successful functioning of these antibacterial systems depends entirely upon an extremely low level of free ionic iron (10(-18) M) in normal tissue fluids. This in turn depends on well-oxygenated tissues where the oxidation-reduction potential (Eh) and pH control the binding of iron by unsaturated transferrin and lactoferrin. Bacterial virulence is greatly enhanced by freely available iron, such as that in fully-saturated transferrin or free haemoglobin. Following trauma a fall in tissue Eh and pH due to ischaemia, plus the reducing powers of bacteria, can make iron in transferrin freely available and abolish the bactericidal properties of tissue fluids with disastrous results for the host. Hyperbaric oxygen is a possible therapeutic measure that could restore normal bactericidal systems in infected tissues by raising the Eh and pH.

Evidence-based guidelines for the management of neutropenia following outpatient hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) involves the transfer of stem cells to establish hematopoiesis in patients who have received myeloablative chemotherapy with or without whole body irradiation. Following high-dose therapy and HSCT, all patients experience a period of neutropenia. Outpatient care delivery models place expanded responsibilities on patients and their families for the management of this treatment side effect. Proactive management of neutropenia is critical to decrease the depth and duration of neutropenia following HSCT, limit exposure to opportunistic and nosocomial pathogens, and ensure prompt intervention should febrile neutropenia or infection develop. Patient and family education, psychosocial support, and coordination of care are key nursing responsibilities.

Are granulocyte colony-stimulating factors beneficial in treating diabetic foot infections?: A meta-analysis

OBJECTIVE

To assess the value of granulocyte colony-stimulating factor (G-CSF) as adjunctive therapy for diabetic foot infections.

RESEARCH DESIGN AND METHODS

We systematically searched the medical literature (including Medline, Embase, LookSmart, and the Cochrane Library) for prospective randomized studies that used G-CSF as an adjunct to standard treatment for diabetic foot infections. Using a conventional meta-analysis, we pooled the relative risks (RRs) for outcomes of interest, including resolution of infection, wound healing, duration of antibiotic therapy, and need for various surgical interventions, using a fixed-effects model.

RESULTS

Five randomized trials, with a total of 167 patients, met our inclusion criteria. The methodological quality of the studies was satisfactory. The investigators administered various G-CSF preparations parenterally for between 3 and 21 days. The meta-analysis revealed that adding G-CSF did not significantly affect the resolution of infection or the healing of the wounds but was associated with a significantly reduced likelihood of lower extremity surgical interventions (RR 0.38 [95% CI 0.20-0.69], number of patients who needed to be treated: 4.5), including amputation (0.41 [0.17-0.95], number of patients who needed to be treated: 8.6). There was no evidence of heterogeneity among the studies or of publication bias, suggesting that these conclusions are reasonably generalizable and robust.

CONCLUSIONS

Adjunctive G-CSF treatment does not appear to hasten the clinical resolution of diabetic foot infection or ulceration but is associated with a reduced rate of amputation and other surgical procedures. The small number of patients who needed to be treated to gain these benefits suggests that using G-CSF should be considered, especially in patients with limb-threatening infections.

G-CSF induces stabilization of ETS protein Fli-1 during myeloid cell development

Granulocyte colony-stimulating factor (G-CSF) is a growth factor that regulates the production and function of neutrophils. G-CSF has been used to treat neutropenia in neonates, pediatric cancer patients, and patients undergoing stem cell transplantation. The regulation of transcription factors mediating G-CSF activity has not been well characterized. The goal of this study was to examine the regulation of the ETS binding protein, Friend leukemia integration site 1 (Fli-1), in myeloid cells treated with G-CSF. Fli-1 has oncogenic properties in humans and mice, and plays a role in vascular and hematopoietic cell development. We previously reported that Fli-1 and the serum response factor bind at adjacent sites within the serum response element-1 of the early growth response gene-1 promoter in the murine myeloid leukemic cell line, NFS60. We also identified that Fli-1 DNA binding increased in G-CSF-treated cells compared with untreated cells. To determine whether the change in binding activity is due to increased Fli-1 transcription or protein stability, we examined endogenous Fli-1 expression in G-CSF-treated or -untreated NFS60 cells. Our results demonstrated that levels of Fli-1 protein, but not RNA, were higher in extracts from cells treated with G-CSF. The increase in Fli-1 protein was also dependent on protein synthesis. Finally, we showed that the half-life of Fli-1 is prolonged in G-CSF-treated cells compared with control-treated cells. These results suggest that G-CSF induces stabilization of Fli-1 protein in myeloid cells, thus proposing a novel mechanism by which hematopoietic growth factors regulate transcription factors.

Neulasta (pegfilgrastim): a once-per-cycle option for the management of chemotherapy-induced neutropenia

Neutropenia is a significant hematologic complication induced by cytotoxic chemotherapy. The clinical consequences of chemotherapy-induced neutropenia are often severe and can be potentially life-threatening. Patients who develop febrile neutropenia often need to be hospitalized, reducing their quality of life and increasing costs. Neutropenia can also compromise the ability to deliver chemotherapy at the full dose and on schedule. To help prevent the occurrence of neutropenia, patients with a high risk of developing chemotherapy-related infections may be given prophylactic colony-stimulating factors. Filgrastim is a recombinant human granulocyte colony-stimulating factor that has been widely used (in over 3 million patients) for over 12 years in the management of neutropenia. Pegfilgrastim is an approved, long-acting, next generation of granulocyte colony-stimulating factor that has similar clinical benefits to filgrastim but has novel pharmacokinetic properties. Pegfilgrastim shows at least comparable safety and efficacy to filgrastim, with the added benefit of simplified once-per-chemotherapy-cycle dosing. In addition, two randomized, controlled pivotal trials have shown that a single dose of pegfilgrastim given once per cycle led to a lower observed incidence of febrile neutropenia following myelosuppressive chemotherapy, compared with daily injections of filgrastim. Clinical trials are currently expanding the clinical experience with pegfilgrastim in a variety of solid tumors and hematologic malignancies. In addition to prevention of chemotherapy-induced neutropenia in 21- and 28-day regimens, future studies are examining the suitability of pegfilgrastim in dose-dense therapy and other cancer settings.

Managing hematologic toxicities: novel therapies

Myelosuppression associated with cancer chemotherapy may lead to neutropenia, anemia, or both, resulting in an increased risk for infection, fatigue, diminished quality of life, and reduced survival. In addition, neutropenia specifically has been shown to result in dose reductions, treatment delays, or both in subsequent chemotherapy cycles. Hematopoietic growth factors have been used effectively as supportive therapy to reduce chemotherapy-associated neutropenia and anemia. New preparations have the potential to improve treatment outcome dramatically. Results from recently reported studies indicate that patients at risk for neutropenia can be safely and effectively treated with pegfilgrastim once per chemotherapy cycle, and that those with anemia can be managed with weekly or biweekly darbepoetin alfa therapy. These new treatments have the potential to reduce the morbidity and mortality associated with opportunistic infections, decrease the requirement for potentially dangerous blood transfusions, and improve the quality of life for patients undergoing cancer chemotherapy. The longer dosing intervals offered by these new preparations may decrease healthcare expenses and enhance patient adherence.

Safety and efficacy of pegfilgrastim in patients receiving myelosuppressive chemotherapy

The major dose-limiting toxicity associated with myelosuppressive chemotherapy is neutropenia, which can be ameliorated with proactive administration of granulocyte colony-stimulating factor (G-CSF). Pegfilgrastim is a long-acting G-CSF, recently approved by the Food and Drug Administration. The efficacy and safety of pegfilgrastim administered once/chemotherapy cycle have been evaluated in clinical trials involving patients treated with myelosuppressive chemotherapy for breast cancer, lung cancer, non-Hodgkin's lymphoma, and Hodgkin's disease. Two pivotal phase III trials in patients with breast cancer showed that pegfilgrastim is as effective as filgrastim regarding the primary efficacy end point, which was duration of grade 4 (severe) neutropenia in cycle 1 of myelosuppressive chemotherapy. Secondary end points were the frequency of fever with neutropenia (febrile neutropenia), duration of neutropenia in cycles 2-4, depth of the absolute neutrophil count (ANC) nadir, and time to ANC recovery in cycles 1-4. Once/cycle pegfilgrastim 100 microg/kg or 6 mg was as safe and effective as daily filgrastim 5 microg/kg in reducing the frequency and duration of severe neutropenia. A trend toward a greater reduction in the overall frequency of febrile neutropenia with pegfilgrastim was observed. The availability of pegfilgrastim simplifies the use of prophylactic G-CSF, with the potential to increase patient convenience and adherence in management of chemotherapy-induced neutropenia.

Economic evaluations of granulocyte colony-stimulating factor: in the prevention and treatment of chemotherapy-induced neutropenia

The prevailing uncertainty about the pharmacoeconomic positioning of granulocyte colony-stimulating factor (G-CSF) in the prevention and treatment of chemotherapy-induced febrile neutropenia has resulted in a number of pharmacoeconomic evaluations published in the past 10 years. These studies vary considerably regarding the approaches used and the results presented. In order to contribute to a clearer pharmacoeconomic positioning of G-CSF, a systematic review of economic evaluations was carried out. The focus of the review was prophylaxis and therapy of chemotherapy-induced neutropenia in patients with cancer. A computerised bibliography search of several databases was conducted yielding 33 studies. The findings demonstrated the cost-saving potential of G-CSF in standard-dose chemotherapy to be limited, with lower costs often seen in the control group. The results of these studies were too heterogeneous to extract a clear recommendation from a cost-saving point of view. The administration of G-CSF after high-dose chemotherapy with stem cell support resulted more often in cost savings in the G-CSF group as compared with standard-dose chemotherapy, illustrating a possible cost-saving potential of G-CSF. In the treatment of established chemotherapy-induced febrile neutropenia, cost savings were found in all studies. This result is surprising but hampered by the small number of studies (n = 5) and remains to be confirmed by more rigourously designed prospective economic analyses. Despite the substantial research on this topic, the economic evaluation of G-CSF is far from being settled and needs further investigation.