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Data from all pts with benign or malignant hematological disorders and solid tumors consecutively diagnosed and treated at the Department of Pediatric Hematology-Oncology (N=532,1999-2014) have been retrospectively recorded and analysed. Pts with superficial thrombosis were excluded from the study. 

In our cohort, a total of 32 pts (median age 5.7 yrs, range 1.1-18.6) developed VTE with the following disease background: acute lymphoblastic leukemia(14), T-lymphoblastic lymphoma(2), RAEB-T/acute myeloid leukemia(1), nephroblastoma(3), neuroblastoma(3), hemophagocytic lymphohistiocytocis(1), autoimmune hemolytic anemia(2) and other rare solid tumors(6). In our cohort, 21 pts had high risk disease features and 6 pts presented with bulky mediastinum involvement. Median time of VTE occurrence from disease diagnosis was 129 days (range 0-4244).  25/32 pts developed DVT during the intensive chemotherapy regimen (16 not in CR). Most commonly used drugs within the last 30 days from DVT diagnosis were Asparaginase and steroids, followed by VCR, MTX, CPM and cisplatin. 13/32 pts had undergone major surgery and no pt received hormone therapy.  In 26/32 pts CVL was placed; median time between CVL placement and VTE occurrence was 60 days (range 0-1352). VTE diagnosis was symptom-driven (n=16) or incidental finding (n=16); in 15 pts VTE was CVL-related (4 with infection) and 6 cases presented in tumor adjacent areas. The most common VTE sites were right atrial and jugular veins (16), subclavian veins and superior vena (2), kidney and inferior vena cava (6), pulmonary embolism (2), femoral and iliac vein (3), cerebral sinovenous thrombosis (5) [ischemic cerebral infracts, cavernous sinus (after XRT), upper sagittal and transverse sinus], with some patients presenting with multiple VTE sites. Additionally, 2 pts presented with VOD, as well. WBC or PLTs count at diagnosis did not have a statistically significant impact on the probability of VTE. Thrombophilia evaluation that was performed in 16/32 pts did not reveal an increased incidence of predisposing factors [factor G20210A variant homozygous or heterozygous (1/1), heterozygous MTHFR variant (8), elevated FVIII (7)]. Treatment consisted mainly of sc LMWHs as anticoagulation therapy in 28/32 pts. Median time of treatment duration was 6 months (range 3-12) and was guided by the continuing presence of CVL, CR status and until establishing vascular patency and stable imaging findings. Within a median follow-up time of 33.8 months (range 2.1-195.1) no VTE recurrence occurred while overall survival was 78.12% with morbidity not related to VTE.

In our study, VTE was not very common among our pediatric haematology-oncology pts and continuation of chemotherapy was feasible in all cases, with no VTE recurrence. Furthermore, thrombophilia evaluation neither revealed an increased incidence of predisposing factors nor altered our therapeutic decisions; thus, extensive baseline screening or DVT prophylaxis are not supported in pediatric pts who can be successfully diagnosed and treated with current recommendations.