Prevention of thrombotic disorders in cancer patients undergoing chemotherapy.

The etiology of thrombosis in malignancy is multi-factorial, and mechanisms include release of procoagulants by tumor cells, comorbid predisposing factors in anti-cancer drugs. The most reliable information on the incidence of thromboembolism in patients receiving chemotherapy comes from breast cancer. The rate of thrombosis in women with Stage II breast cancer receiving adjuvant chemotherapy is approximately 5%. The highest risk is in postmenopausal women and the addition of tamoxifen to chemotherapy increases the thrombotic risk over chemotherapy alone. The rate of thrombosis in metastatic breast cancer is likely to be much higher than that in Stage II breast cancer. Cancer patients with central venous catheters, e.g. Hickman, portacath, should receive 1 mg of warfarin daily. A recent trial has demonstrated that low molecular weight heparin can prevent catheter-related clots. There has been only one trial conducted evaluating prophylaxis in ambulatory cancer patients receiving chemotherapy. In this study, very low dose warfarin (INR 1.3-1.9) substantially reduced the risk of venous thromboembolism in breast cancer patients receiving chemotherapy.