One of the most complex situations in the treatment of cancer-associated thrombosis is represented by oncological patients with thrombocytopenia. Patients with hematological neoplasms and patients with solid cancer undergoing chemotherapy frequently show reduced platelet count, sometimes even below 50.000/mm3. In general, it is suggested to use low molecular weight heparin in these patients, because of the short half-life and the possibility to modulate the dosage. It is commonly believed that therapeutic doses of low molecular weight heparin can be used above the cut-off of 50.000/mm3, if there are no concomitant contraindications, and that the dose should be reduced to 50% below this cut-off. Further dose reduction or treatment interruption is necessary for very low platelet counts. Alternatively, platelet transfusions are suggested with the aim to keep a platelet count between 40.000 e 50.000/mm3, in order to allow the full therapeutic dose of heparin. Lacking clear scientific evidence, these indications are based on experts’ opinion.
During the ICTHIC congress, interesting data have been presented from a systematic review of the literature aiming at identifying and analyzing studies in which the two therapeutic strategies (progressive reduction of anticoagulant dose or platelet transfusion) have been compared.
Among the 134 studies initially identified (until September 2017), only 2 studies actually described the outcomes separately for these two cohorts of patients treated with different strategies. Overall, the two studies recruited 121 patients; among these 44 (36%) received therapeutic dose of low molecular weight heparin, 49 (40%) received a dose adjusted on platelet count and 26 (21%) no anticoagulant treatment. Two patients were excluded because they received oral anticoagulant treatment. Thromboembolic recurrences were more common among those patients receiving low molecular weight heparin at reduced dose (15 events, 47%) or not receiving any anticoagulant treatment (10 events, 31%), compared to those patients who received the full therapeutic dose (7 events, 22%). Major bleeding were 10 (56%) with low molecular weight heparin at dose adjusted, 2 (11%) without treatment and 6 (33%) with full anticoagulant dose, respectively.
Considering the small sample size and the methodological limitations, the authors could not draw strong conclusions, but they pointed out the need for further studies enrolling thrombocytopenic oncological patients, possibly with a randomized design. This data however indicate that the risk of recurrent thrombotic events, as well as the bleeding risk during anticoagulant treatment, is not irrelevant in thrombocytopenic oncological patients.
References
Samuleson Bannow B et al. Management of anticoagulation of cancer-associated thrombosis in patients with thrombocytopenia. Thromb Res 2018(164):S203:PO-16