Incidence of Post-Thrombotic Syndrome Following Asymptomatic Thrombosis in Survivors of Childhood Acute Lymphoblastic Leukemia.
Authors: Kuhle Stefan , Spavour Maria , Halton Jacqueline , Massicotte Patricia , Cherrick Irene , Dix David , Mahoney Donald , Desai Sunil , Mitchell Lesley G. 
Published: April 2020

Abstract
BACKGROUND: Asymptomatic deep venous thrombosis (DVT) are well-known complications of treatment of acute lymphoblastic leukemia (ALL) in children. However, the clinical significance of radiographically detected, asymptomatic DVT is unclear and controversial, as there are no studies on long-term outcome of asymptomatic DVT in children available. There are two likely reasons for the studies not being done in this area. First, there is a lack of defined cohorts of pediatric patients screened for DVT and secondly, there is a great deal of difficulty in following patients over many years. The study, Prophylaxis with Antithrombin Replacement in Kids with ALL treated with L-Asparaginase (PARKAA) was a multicentre randomized controlled trial in which children with ALL were screened for DVT. As survivors of childhood cancer, the PARKAA cohort continues to be followed in their respective centers. Therefore, establishment of the PARKAA cohort (1997–99) and the ability to locate these patients provided a unique opportunity to study the long-term outcome of asymptomatic DVT.
OBJECTIVE: To assess the incidence of PTS in children with ALL who previously had an asymptomatic DVT. The objective were approached in two ways. Firstly, to assess the outcome of asymptomatic DVT by determining the prevalence of PTS in children with a history of ALL with radiographically diagnosed DVT (PARKAA cohort); secondly, to corroborate the findings by determining the prevalence of PTS in an unselected group of survivors of childhood ALL.
METHODS: Cross-sectional study in two separate populations: Group I comprised of children enrolled in the PARKAA multicentre study who had been screened for, and diagnosed with, DVT in the upper venous system. Group II consisted of non-selected patients &lt; 21 years with a history of ALL followed at Stollery Children’s Hospital, Edmonton. Patients were invited for a follow-up at their treatment centre (Group I) or were assessed for PTS childhood cancer survivor clinic (Group II). PTS was assessed by two of the investigators (Group I) or by the attending oncologist (Group II), respectively, using a standardized scoring sheet.
RESULTS: Group I: 13 PARKAA patients with a history of ALL and objectively diagnosed DVT were assessed for PTS (4 males; median age 11.9 years; median age at diagnosis of ALL 4.4 years). 7/13 patients had PTS (54%, 95%CI 25;81). All patients with PTS had collaterals on examination, 3 also had increased arm circumference. Group II: 41 patients with a history of ALL were enrolled (61% males; median age at diagnosis 3.0 years; 28% high-risk, 67% standard risk). Mean length of follow-up since diagnosis was 9.5 years. PTS was diagnosed in 10/41 (24%; 95%CI 11–38) patients. All patients with PTS had collaterals on examination, 5 (50%) also had increased arm circumference.
CONCLUSIONS: There is a clinically significant prevalence of PTS in children with a history of ALL and radiographically diagnosed DVT. A significant proportion of survivors of ALL develop PTS, indicating previously undiagnosed DVT in this population.