Therapeutic significance of a D-dimer cut-off level of >3 µg/ml in colorectal cancer patients treated with standard chemotherapy plus bevacizumab.

OBJECTIVE The risk of venous thromboembolism has been reported to increase when receiving bevacizumab. Many cancer patients are reported to have elevated D-dimer levels. It is not clear what D-dimer level might indicate an increased risk of venous thromboembolism in the colorectal cancer patients treated with bevacizumab-containing chemotherapy. METHODS The D-dimer levels and any event concurrent with an elevated D-dimer level were evaluated in patients receiving bevacizumab. The D-dimer cut-off level was determined using the receiver-operating characteristic analysis. The selection criteria were as follows: histologically proven metastatic and unresectable colorectal adenocarcinoma; no prior chemotherapy containing bevacizumab; D-dimer test performed repetitively on the baseline and during bevacizumab administration; no venous thromboembolism identified at the baseline; and enhanced computed tomographic scan performed every 2 months. RESULTS Sixty-nine patients were included. The chemotherapy regimens with bevacizumab included the regimen of 5-fluorouracil, leucovorin and oxaliplatin (FOLFOX), the regimen of 5-fluorouracil, leucovorin and irinotecan (FOLFIRI), and leucovorin-modulated 5-fluorouracil. The median baseline D-dimer level was 1.2 µg/ml. The appropriate D-dimer cut-off level was 3 µg/ml with the negative predictive value of 98% and relative risk of 6.9. Twenty-one of 69 patients showed elevated D-dimer levels of >3 µg/ml, with 11 patients for unknown reasons, 6 with tumor progression, 3 with venous thromboembolism and 1 with sepsis. In the remaining 48 patients whose D-dimer levels were ≤3 µg/ml, only one patient developed a venous thromboembolism. CONCLUSIONS A D-dimer cut-off level of 3 µg/ml might be a useful indicator level to exclude venous thromboembolism or show an increased risk for venous thromboembolism in colorectal cancer patients treated with bevacizumab-containing chemotherapy.