Increasing Incidence and Recurrence Rate of Venous Thromboembolism in Paediatric Oncology Patients in One Single Centre Over 25 Years.

Venous thromboembolism (VTE) is a serious complication in paediatric oncology patients. To identify the incidence, risk factors and recurrence rate of VTE in paediatric oncology patients, an observational, retrospective cohort study of all consecutive children (≤18 years) with malignancies, treated at the Emma Children's Hospital Academic Medical Centre between January 1989 and December 2013, was done. A matched case-control study in children with lymphomas was performed, to identify thrombotic risk factors. Cumulative recurrence-free survival after first VTE was estimated by the Kaplan-Meier method. Of the 2,183 children included (male: female = 1.4:1.0; median age, 6.6 years) with cancer, 78 patients developed VTE (3.6%; 95% confidence interval [CI], 2.8-4.4). The incidence increased from 0.8% (4/478, 95% CI, 0.0-1.6) between 1989 and 1993 to 10.4% (44/423, 95% CI, 7.6-13.4) between 2009 and 2013. Independent risk factors for VTE were age ≥ 12 years, acute lymphoblastic leukaemia (ALL) and lymphoma. The case-control study in lymphoma patients showed a trend for increased VTE incidence in stage IV lymphoma. Twelve (15.4%) patients developed recurrent thrombosis, 7 patients while on therapeutic or prophylactic anticoagulation. The cumulative recurrence-free survival after first VTE was 88.5, 87.1 and 80.6% after 1, 5 and 10 years, respectively. In conclusion, we demonstrated an increasing incidence of VTE in children with malignancies, with age ≥ 12 years, ALL and lymphoma as independent risk factors. The elevated recurrence rate underlines the importance of full anticoagulant therapy and might warrant prophylactic anticoagulation after first VTE during cancer treatment.