Using a Blood Test and Software Tool to Guide Treatment for Venous Thromboembolism

The purpose of this study is to find out whether a software tool, ctDNA/VTE (Venous Thromboembolism) risk score model, is an effective way to predict the likelihood of VTE coming back in people who have received anticoagulant treatment.

Inclusion Criteria: * Age ≥ 18 with a history of cancer-associated VTE (objectively confirmed symptomatic or incidental/unsuspected proximal lower-limb DVT, symptomatic pulmonary embolism \[PE\] or incidental PE in a segmental or more proximal pulmonary artery) and completion of between 3 and 12 months of anticoagulation with a therapeutic dosing of enoxaparin, dalteparin,rivaroxaban, or apixaban without current VTE-related symptoms (imaging to confirm resolution not required). Diagnosis of DVT requires evidence of one or more filling defects at compression ultrasonography, venography, CT venography, or MR venography involving at least the popliteal or more proximal veins. Diagnosis of PE requires an intraluminal filling defect in segmental or more proximal arteries. * Diagnosis of one of the following solid tumors in either advanced (i.e. unresectable) stage or receiving systemic anticancer treatment within six weeks of enrollment (maintenance therapy included): * breast cancer regardless of cytotoxic-chemotherapy status * hepatobiliary cancer regardless of cytotoxic-chemotherapy status * prostate cancer regardless of cytotoxic-chemotherapy status * non-small cell lung cancer with cytotoxic-chemotherapy received within 30 days * pancreatic cancer with cytotoxic-chemotherapy received within 30 days * bladder cancer with cytotoxic-chemotherapy received within 30 days * Signed and dated informed consent by study participant/Legally Authorized Representative (LAR). Exclusion Criteria: * Contraindication to ongoing anticoagulation * Contraindication to discontinuation of anticoagulation (examples include but not limited to: known antiphospholipid syndrome or factor V leiden, active arterial thrombus, catheter-associated thrombus, on anticoagulation for atrial fibrillation or other non-oncologic reasons) * History of major bleeding in the last six months (major bleeding defined as fatal bleeding, and/or symptomatic bleeding in a critical area or organ, such as intracranial, intraspinal, intraocular, retroperitoneal, intra-articular or pericardial, or intramuscular with compartment syndrome; bleeding that necessitates acute surgical intervention; bleeding causing a fall in hemoglobin levels of 1.24 mmol/L (2 g/dL or greater) or more; or bleeding leading to a transfusion of 2 U or more of whole blood or red cells). * Known diagnosis of disseminated intravascular coagulation (DIC) * Suspicion for tumor thrombus on the imaging leading to original diagnosis of VTE * Enrolled in hospice care * Currently has inferior vena cava (IVC) filter * Diagnosis of an active hematologic malignancy