Possible mechanism of vinblastine-induced thrombocytosis

A Review and Assessment of Drug-Induced Thrombocytosis

OBJECTIVES

The purpose of this article is to review the current literature on drug-induced thrombocytosis with the goal of critically assessing causality and providing a comprehensive review of the topic. Thrombopoietic growth factors, such as thrombopoietin-receptor agonists (romiplostim and eltrombopag) and erythropoietin are not included in our review.

DATA SOURCES

The literature search included published articles limited to the English language and humans in MEDLINE, EMBASE, and Web of Science databases. MEDLINE/PubMed (1966 to September 2018) was searched using the MeSH terms thrombocytosis/chemically-induced and thrombocytosis/etiology. EMBASE (1980 to September 2018) was searched using the EMTAGS thrombocytosis/side effect. Web of Science (1970 to September 2018) was searched using the search term thrombocytosis. References of all relevant articles were reviewed for additional citations and information.

STUDY SELECTION AND DATA EXTRACTION

Review articles, clinical trials, background data, case series, and case reports of drug-induced thrombocytosis were collected, and case reports were assessed for causality using a modified Naranjo nomogram.

DATA SYNTHESIS

Drug-induced thrombocytosis, a form of reactive thrombocytosis cannot be easily differentiated from more common etiologies of reactive thrombocytosis. In all, 43 case reports of drug-induced thrombocytosis from a wide variety of drugs and drug classes were reviewed using a modified Naranjo probability scale that included criteria specific for thrombocytosis.

CONCLUSIONS

Drug-induced thrombocytosis is a relatively rare adverse drug reaction. The strongest evidence of causality supports low-molecular-weight heparins and neonatal drug withdrawal. Weaker evidence exists for all-trans retinoic acid, antibiotics, clozapine, epinephrine, gemcitabine, and vinca alkaloids.

Drug-induced thrombocytosis

Thrombocytosis is generally defined as platelet counts greater than 400,000/mm3. Thrombocytosis can be either primary or secondary. Adrenalin was one of the first drugs noticed to cause platelet elevations, probably due to demargination of platelets in the pulmonary vasculature. Vinca alkaloids have the most convincing data to show that they can induce thrombocytosis through their thrombocyte-stimulating properties. Miconazole has been implicated in causing thrombocytosis and has a documented case validated by drug rechallenge. Iron, predictably, can cause a transient thrombocytosis. The beta-lactam antibiotic data are very difficult to interpret due to the possibility of an acute-phase reaction in an infected patient being the cause of the thrombocytosis.

Megakaryocytes in cubital venous blood in patients with chronic myeloproliferative diseases

33 patients with chronic myelo-proliferative disease were investigated for megakaryocytes in cubital venous blood. 6 Patients had chronic myeloid leukaemia, 11 polycythaemia vera and 16 myelofibrosis. In all patients, a significantly higher number of megakaryocytes than in normal adult humans was found. In patients with chronic myeloid leukaemia and myelofibrosis, an increased number of intact megakaryocytes was found, indicating thrombopoiesis in the peripheral part of the upper extremity. 2 patients with myelofibrosis showed a % of intact megakaryocytes greater than 25, as found in blood from the inferior vena cava in normal adults. In patients with chronic myeloid leukaemia, some of the megakaryocytes were smaller than normal, whereas in myelofibrosis, some of the megakaryocytes were larger than normal, with increased lobulation of nuclei. Active thrombopoiesis in the peripheral part of the extremities can be of great importance, when splenectomy is considered in treatment of myelofibrosis.

Vindesine: phase II evaluation in colon cancer and description of its platelet stimulating activity

Fifteen previously treated patients with measurable metastatic colon carcinoma were entered into a phase II study of vindesine, 3 mg/m2/week IV. Fourteen patients were evaluable for response. No objective tumor response was observed; however, seven patients experienced stable disease lasting 9, 10, 13, 15, 16, 19, and 26 weeks. Neurologic toxicity was the most common nonhematologic side-effect noted, manifesting as abdominal pain, constipation, paralytic ileus, or paresthesias. Leukopenia was observed in 16% of the 104 weekly courses. Nine patients had a 50% increase of their platelet counts above their pretreatment platelet counts; six patients had a doubling of their pretreatment platelet counts. Mean platelet counts revealed a linear increase with successive treatments during the initial 8 weeks of therapy. Serial CEA determinations demonstrated a parallel relationship with clinical progression in six of seven patients.

Serum thrombopoietic activity following administration of vinblastine

A possible role of humoral factors in the pathogenesis of vinblastine-induced thrombocytosis was examined. The thrombopoietic activity in serum of experimental animals was tested for its ability to stimulate the incorporation of 75-Se-selonemethionine into platelets of thrombocythaemic mice. The administration of low doses (0.1--0.5 mg/kg body wt.) of vinblastine to rabbits caused a significant increase in serum thrombopoietic activity. Higher doses of vinblastine (1--5 mg/kg body wt.) also increased the serum thrombopoietic activity, but this increase was preceded by a transient drop in the platelet count of peripheral blood. This thrombocytopenia could have been a stimulus for an increase in thrombopoietic activity, through a compensatory feedback mechanism. The vinblastine-induced increase in thrombopoietic activity was abolished by bilateral nephrectomy but not by bilateral ureteral ligation. These data suggest that kidney tissue may be a major source of the serum thrombopoietic factors.

Evidence that stimulation of megakaryocytopoiesis by low dose vincristine results from an effect on platelets

Appropriate low dosages of vincristine stimulate megakaryocytopoiesis and produce thrombocytosis. In this study of the thrombocytotic action of vincristine, administration of a single dose of 0.1 mg/kg to rats produced an increase in megakaryocyte concentration, diameter and 24 h [3H]thymidine labelling index. Transfusion of one body equivalent of platelets from normal donors prevented stimulation of megakaryocytopoiesis by vincristine whereas platelets from vincristine-treated donors did not. These results suggest that vincristine stimulates megakaryocytopoiesis by altering the functional role of circulating platelets in the regulation of thrombopoiesis.

The effects of colcemid on hematopoiesis in the mouse

Colcemid was found to induce a dose and schedule dependent marrow magakaryocytosis and peripheral thrombocytosis. The response could be divided into early and late components. The early component appears to have been due to a direct stimulatory effect, probably by enhancement of endoreduplication in metaphase arrested megakaryocyte precursors. The ealy stimulatory response was blunted on toxic drug schedules. In contrast, the late component of the thrombopoietic response was demonstrated best on the most toxic drug schedules. It coincided temporally with the reactive restoration of the mononuclear marrow and blood cell elements, respectively. Thus, the late component appears to be a nonspecific rebound phenomenon. On comparing the thrombopoietic properties of Colcemid with those of the vinca alkaloids in experimental systems, the former appears to have a more favorable therapeutic index. The data suggest that colchicine and its derivatives may be useful agents in the treatment of clinical thrombocytopenic states.

Reversible thrombocytosis and anemia due to miconazole therapy

Miconazole was administered intravenously in six consecutive patients with, active coccidioidal infection. Such treatment was associated with progressive anemia and thrombocytosis. The hematological abnormalities appeared to be dose related and potentially reversible. Bone marrow studies demonstrated erythroid hypoplasia and increased or active platelet production in three subjects. No hemorrhagic or thrombotic episodes were identified. It is suggested that careful hematological monitoring be performed in subjects undergoing systemic miconazole therapy.

Restoration of effective hemopoiesis preceding suppression of leukemic clone in myeloblastic leukemia

A 63 year old Caucasian woman presented with myeloblastic leukemia and a hyperdiploid C group chromosome change in 10 per cent of marrow metaphases. Treatment iwth cytotoxic agents resulted in an increased percentage (52 per cent) of these hyperdiploid marrow cells. Furthermore, the marrow continued to show leukemic fearures morphologically and in culture. Despite the indications of persistence or progression of the hyperdiploid, putatively leukemic line at cessation of chemotherapy and for a period of time thereafter, remission was achieved and blood and marrow cell numbers one year after cessation of all treatment are normal. The hyperdiploid line is no longer detectable. This case raises questions concerning the mechanism whereby remission is attained in some cases of acute leukemia and is discussed in terms of the restoration of normal hemopoiesis eliminating the leukemic process.