Background: Intravascular extension to the inferior vena cava and right atrium is a well-recognized complication of Wilms tumour (WT), with incidence of 4-10% and 0.7 -1%, respectively. Neoadjuvant chemotherapy is commonly used to decrease the size of the tumour thrombus prior to resection in cases of extensive vascular extension. Complications of intravascular tumour thrombus include pulmonary embolism, disease progression despite chemotherapy, and death.

Aims: Explore the utility, efficacy, and safety of anticoagulation in patients with intravascular extension of WT.

Methods: Searches conducted in PubMed used the following terms: Wilms*, anticoagula*, tumor thrombus, intracaval, and intra-atrial. Studies were included if patients had WT with intravascular extension. Data was retrieved from 8 case reports, 2 case series, and 14 retrospective analyses, one of which was abstract-only.

Results: Intravascular extension of WT was reported in 482 cases (6.9%). Pulmonary embolism (PE) was described in four patients (retrohepatic[1], intracaval[1], and intra-atrial[2]) across three studies. Disease progression was reported in 13 patients in four studies and death was reported in 30 cases across all studies. Of 24 retrieved articles, two reported anticoagulant use adjunctively with chemotherapy: a retrospective analysis in 9/29 patients and one case report. The only documented complication was minor bleeding in one patient (10%). Majority of cases did not report concurrent use of anticoagulation, apart from instances when patients underwent cardiopulmonary bypass or postoperatively after inferior vena cava manipulation.

Conclusions: Tumor thrombosis is an important complication in pediatric WT patients, however minimal literature exists addressing optimal management strategies including the utility of anticoagulation therapy. Literature suggests that renal vein thrombosis can lead to kidney damage. Use of anticoagulation may be considered to prevent propagation of the clot to the contralateral kidney. Risk of bleeding and of acquired von Willebrand Disease must also be considered prior to anticoagulation therapy. As limited literature is available, further study is needed.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/a-comprehensive-review-of-tumour-thrombus-in-pediatric-wilms-tumour-patients/