Management of Cancer-Associated Venous Thromboembolism in Patients with Concomitant Thrombocytopenia: A Survey of Canadian Practitioners

INTRODUCTION: Both venous thromboembolism (VTE) and thrombocytopenia are common in cancer patients. The management of cancer-associated thrombosis (CAT) in the context of thrombocytopenia remains an important area of clinical equipoise; a paucity of evidence to support management strategies implies that guidelines and consensus statements rely on expert opinion. We aimed to characterize the practices of Canadian practitioners in the treatment of CAT in thrombocytopenic patients. METHODS: In May to July 2014, we conducted an electronic survey of Canadian practitioners likely to participate in the management of CAT. The survey was comprised mainly of open- ended questions. An estimated 300 members of the Canadian Hematology Society and Thrombosis Canada were invited to complete the survey. RESULTS: Respondents: 31 practitioners participated in the survey. 17 (55%) were board- certified hematologists, 10 (32%) were internists, and 3 (10%) were general practitioners. 14 (45%) had been in practice for < 5 years, and 15 (48%) had been practicing for >15 years. The majority of respondents, 27 (87%), worked in tertiary-care centers or university-affiliated institutions. 17 (55%) had self-reported expertise in thrombosis. Regarding frequency of encounters, 10 (32%) of participants reported seeing > 20 patients with CAT and thrombocytopenia per year, while 8 (26%) reported seeing <5 such patients per year. Management strategies: The median (IQR) platelet count above which respondents reported administering VTE prophylaxis, to patients in whom this would otherwise be indicated, was 25 (20, 30) . The median (IQR) platelet count above which respondents would administer full-dose anticoagulation for treatment of established CAT was 50 (40, 50); for reduced-dose anticoagulation, this threshold was 30 (20, 50). For patients with CAT and thrombocytopenia, 21 (68%) reported the use of sub-therapeutic doses of anticoagulation as a management strategy. A majority of respondents, 20 (65%), reported that there were cases in which they elect to withhold all anticoagulation due to thrombocytopenia in patients with acute CAT, in the absence of bleeding. 20 (65%) respondents reported using platelet transfusions to achieve a higher platelet count target than would otherwise be indicated in order to facilitate anticoagulation in patients with CAT and concomitant thrombocytopenia; the median platelet count target in such cases was 35 (30, 50). 14 of 20 respondents reporting the use of platelet transfusions for this purpose employed this transfusion strategy to facilitate full-dose anticoagulation, while a minority (n=6) administered reduced dose anticoagulation in this setting. Those who were newer to practice (< 5 year in practice) and those who reported treating higher volumes of patients with CAT and thrombocytopenia (>10 patients per year) were more likely to employ prophylactic platelet transfusions to facilitate the administration of anticoagulation (86% vs. 47%, p= 0.03, for newer to practice; 87% vs. 44%, p= 0.03, for those treating >10 patients per year) The use of three case studies, for which participants were asked to outline a management strategy, revealed considerable variability in practice (Figure 1). CONCLUSIONS: While most respondents' practices were somewhat consistent with published consensus statements and recommendations, strategies for anticoagulation of CAT in thrombocytopenic patients were highly variable among Canadian practitioners. High quality studies are required to establish an evidence-based approach to this uncommon clinical entity. Figure 1. Initial management approach of respondents for 3 cases of CAT with thrombocytopenia. LE-DVT= lower extremity deep vein thrombosis; PE= pulmonary embolism; UE-DVT= upper-extremity deep vein thrombosis; IVC= inferior vena cava. Figure 1. Initial management approach of respondents for 3 cases of CAT with thrombocytopenia. LE-DVT= lower extremity deep vein thrombosis; PE= pulmonary embolism; UE-DVT= upper-extremity deep vein thrombosis; IVC= inferior vena cava. Disclosures Kuo: Novartis Canada: Honoraria; Alexion: Honoraria.

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