Colorectal cancer patients with central venous catheters (CVC) for pharmacokinetic modulating chemotherapy (PMC) have a substantial risk of venous thromboembolism (VTE). PMC, designed as a hybrid of lower metronomic and higher shorter plasma 5-FU concentrations, has been clinically successful. To determine the effectiveness and safety of D-dimer tests and multidetector-row CT (MDCT) for diagnosis in cancer patients with suspected VTE, we carried out a clinical outcome study on PMC outpatients. Patients received a D-dimer test before and after commencing the PMC regimen. MDCT was performed additionally if the D-dimer test appeared positive or showed signs of VTE. When CT results were positive for thromboembolism, anticoagulation was started. The overall prevalence of VTE in PMC patients was 2.0% (7 of 350 patients). In this study, 34 out of 102 colorectal cancer patients gave a positive D-dimer test (33.3%). CT identified venous thrombi in 2 of the 102 patients (2.0%), mural thrombosis on catheterized veins in another 3 patients (2.9%), and endothelial hyperplasia on catheterized veins in 8 patients (7.8%). The catheters of these patients did not show any significant abnormalities. Patients with negative D-dimer tests showed no signs or symptoms of VTE. In colorectal cancer patients receiving continuous 5-FU infusion via CVC, a D-dimer test can be safely used as the primary diagnostic test for ruling out VTE. We suggest 7.0 µg/ml as the D-dimer cut-off value. Thromboprophylaxis should be considered in the patients showing values >7.0 µg/ml.

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